Effective Diets for MRSA Infection

Staph Infection Secrets By Dr. Walinski

Discover a Simple 3-Step Program to Permanently Eradicate Mrsa & Staph Infections Without Using Antibiotics. Here is what's provided in Staph Infection Secrets. Get Rid of Your Staph / Mrsa Infection. Best ways to quickly get rid of the most common conditions caused by Mrsa and Staph, such as: Impetigo, Cellulitis, Folliculitis, Boils / Carbuncles and more. An easy remedy for nasal infections than can completely eradicate the presence of the bacteria in less than 7 days. How to treat internal infections using a naturally occurring powerful antibiotic with a proven success rate. Learn how to get the most out of Western medicine learn what kinds of treatment is available and how to work with your doctor for best results. More here...

Staph Infection Secrets By Dr Walinski Overview

Rating:

4.6 stars out of 11 votes

Contents: 82 Pages EBook
Author: Dr. Hubert Walinski
Official Website: www.staphinfectionsecrets.com
Price: $29.95

Access Now

My Staph Infection Secrets By Dr Walinski Review

Highly Recommended

All of the information that the author discovered has been compiled into a downloadable ebook so that purchasers of Staph Infection Secrets By Dr. Walinski can begin putting the methods it teaches to use as soon as possible.

When compared to other ebooks and paper publications I have read, I consider this to be the bible for this topic. Get this and you will never regret the decision.

Staphylococcus aureus

Staphylococcus aureus has long been recognized as one of the most important human pathogens. It colonizes and infects both hospitalized and healthy people in the community (Waldvogel 2000). It is responsible for a wide range of infections ranging from skin and soft tissue infections to bacteraemia, infections of the central nervous system, bone and joints, skeletal muscles, respiratory and urinary tracts, and infections associated with intravascular devices and foreign bodies. Before the introduction of penicillin in the early 1940s, invasive S. aureus infections had mortality over 90 (Smith and Vickers 1960). At that time, S. aureus strains were fully susceptible and penicillin treatment cured formerly untreatable infections (Abraham et al. 1941), but resistance, mediated by a plasmid-borne beta-lactamase capable of degrading the antibiotic, quickly emerged and spread. The same history happened to other antibiotics (streptomycin, tetracycline, chloramphenicol, erythromycin) soon...

Box 78 Spread of MRSA

Military recruits at training facilities are at risk for community-associated (CA) MRSA. Between October 2000 and June 2002, a large U.S. military facility recorded 235 cases of CA-MRSA. In November 2002, military authorities implemented a variety of hygienic measures including an emphasis on hand washing and showering. In addition, sharing personal items was prohibited, and antibiotic therapy was instituted to eliminate nasal colonization. The outbreak ended in December 2002. In many of these cases, infections were on arms and legs where skin abrasions were expected from training exercises.168 Another example surfaced in September 2005 when five members of the St. Louis Rams professional football team reported MRSA infections at turf-abrasion sites. The abscesses were large (more than 2 inches 5 cm in diameter) and required surgical incision and drainage. Molecular analysis of the infecting bacteria showed that all cases were due to USA300, which was common in the community. A...

Methicillin Resistant Staphylococcus aureus

Overall, S. aureus is reported to be the most common cause of bacterial infections involving the bloodstream, lower respiratory tract (CAP and HAP), and skin soft tissue.84 It is reported to be the leading organism responsible for VAP in Europe.85 VAP due to MRSA significantly extends ICU length of stay and increases hospital costs.86 A wide array of virulence mechanisms, an ability to persist in different environments, and an extraordinary potential to develop antimicrobial resistance contribute to the success of this organism as a human pathogen.87,88 Naturally occurring MRSA isolates were identified soon after methicillin was introduced. Since methicillin resistance in S. aureus was first reported in the early 1960s, the proportion of Gram-positive pathogens that are resistant to antimicrobial agents continues to increase both in the hospital setting, particularly in the ICU, and in the community.84 In 1991, MRSA accounted for 35 of isolates in the United States, but that incidence...

Methicillin Resistant Staphylococcus aureus MRSA

Reports of penicillin resistance in S. aureus began to appear within only a few years of the introduction of penicillin in the early 1940s, and now, 60 years later, virtually all staphylococcal strains have acquired genes that allow them to produce b-lactamases that make them resistant to the natural penicillins, aminopenicillins, and the so-called anti-pseudomonal penicillins (insert reference). Oxacillin and methicillin were developed and successfully used clinically in the early 1960s, but over relatively short periods of time, resistance to oxacillin and methicillin emerged. Similar to penicillin-resistant organisms, these strains, collectively called methicillin-resistant S. aureus or MRSA have appeared and spread, in a clonal fashion, initially within the hospital environment and more recently in the community, where new strains have been described.

Community Associated Mrsa Camrsa

MRSA began to be detected as a common cause of infection in the community in persons who had not had contact with the health-care system as recent as the mid-1990s and prevalence is increasing rapidly (CDC 2003 Kazakova et al. 2005 Moran et al. 2006). Organisms responsible for these infections are new strains as defined by molecular typing and have spread throughout the globe. These MRSA isolates express the smaller and more basic type IV SCCmec and are less often multi-resistant. Strains of CA-MRSA show various degrees of susceptibility to clindamycin, TMP-SMX, and tetracyclines. They have a high prevalence of genes encoding the Panton-Valentine leukocidine, an exotoxin associated with necrotizing skin and pulmonary disease and abscess formation and have been associated with significant morbidity and mortality. The first report of CA-MRSA from Latin America was from Brazil in 2003 (Ribeiro et al. 2005). Three well-characterized strains harbored the SCC mec type IV, Panton-Valentine...

Staphylococcal Biofilms

2 Biofilms and Staphylococcal 2.3 Other 2.4 Interaction of Staphylococci with Other Pathogens 3 The Molecular Basis of Biofilm Formation in 4 Regulation of Biofilm Formation in 5 Physiology of Staphylococcal Biofilms Lessons from Transcriptional Profiling 220 7.1 Interfering with Essential Staphylococcal Biofilm Factors Abstract Staphylococcus epidermidis and Staphylococcus aureus are the most frequent causes of nosocomial infections and infections on indwelling medical devices, which characteristically involve biofilms. Recent advances in staphylococcal molecular biology have provided more detailed insight into the basis of biofilm formation in these opportunistic pathogens. A series of surface proteins mediate initial attachment to host matrix proteins, which is followed by the expression of a cationic glucosamine-based exopolysaccharide that aggregates the bacterial cells. In some cases, proteins may function as alternative aggregating substances. Furthermore, surfactant peptides...

Biofilms and Staphylococcal Infections

The Nosocomial Infections Surveillance System (http www.cdc.gov ncidod hip NNIS 2004NNISreport.pdf) recognizes S. aureus and CoNS (coagulase-negative staphylococci, i.e., S. epidermidis and most other staphylococci other than S. aureus) as the most frequently isolated nosocomial pathogens from intensive care unit patients. An extremely high percentage of these isolates are resistant to methicillin (89 CoNS compared to 59.5 for S. epidermidis). In addition to specific antibiotic resistance, which is based on the acquisition of genetic resistance factors and may be chromosomally, or more often plasmid-encoded, staphylococci have nonspecific mechanisms of resistance, of which biofilm formation is undoubtedly the most important.

Interaction of Staphylococci with Other Pathogens in Mixed Species Medical Biofilms

In contrast to many other medical biofilms, such as multispecies dental plaque formation, biofilm-associated infections with staphylococci are usually not mixed with other species (Arciola et al. 2005). In addition, it is rare to find more than one strain in an infection. A possible explanation for this phenomenon is interspecies communication by quorum-sensing signals, which in staphylococci leads to inter-species inhibition of virulence factor expression (Ji et al. 1997). Similarly, bacterial interference by quorum-sensing signals may explain why P. aeruginosa outgrows S. aureus and other bacterial pathogens in progressed lung infections (Renders et al. 2001 Qazi et al. 2006). However, these phenomena are poorly understood and there may be a simpler explanation based on the evolutionary adaptation of the bacteria to a specific environment, such as of S. epidermidis on the skin.

Precautions Can Be Taken with MRSA

MRSA emerged in the 1960s as a cause of healthcare-associated infections (HA-MRSA). Thirty years later, a different form of MRSA appeared in the community (CA-MRSA), generally among children and young adults. The organism invades wounds and even hair follicles. There, it establishes abscesses, which are often treated successfully by surgical drainage. Skin and soft-tissue infections are by far the most common consequences of CA-MRSA. Severe cases, such as deep-tissue infections and pneumonia, require antibiotic treatment. Because MRSA is spread by contact, avoiding the pathogen is largely a matter of hygiene, as discussed in previous chapters. (Another example is given in Box 12-4.) Antiseptics may be useful when applied to skin abrasions as prophylaxis. Tests with liquid cultures of MRSA indicate that a mixture of benzethonium chloride with essential oils is more bactericidal than neomycin polymyxin B or polymyxin B gramicidin combinations.257 Keep bacterial numbers down by cleaning...

Box 125 MRSA in Pigs Their Handlers and Food

In Northern Europe, where high-density food animal farming occurs, pigs are emerging as a reservoir for a type of MRSA called CC398. (This strain of MRSA is also found in horses and dogs in Austria and Germany.) CC398 exhibits resistance to six or seven drugs, including tetracycline, a compound commonly used to promote growth of food animals. CC398 first surfaced in 2004 in France where four pigs and a healthy pig farmer were colonized. The strain subsequently appeared in Holland and Denmark, two countries that employ a search and destroy policy to control MRSA. (Thirty-nine percent of Dutch pigs are thought to carry MRSA.) CC398 is traced by DNA methods, which now reveal pig-to-human and human-to-human transfer. In a study of veterinarians, 4 (179 total tested) carried the bacterium. Because Denmark has a sizable pig population (25 million are slaughtered each year), pigs could serve as a reservoir for human infection.261 In a 2006 report, roughly 80 raw meat samples, obtained from...

Interfering with Essential Staphylococcal Biofilm Factors

An ideal anti-biofilm drug in staphylococci would inactivate a factor that is indispensable for every case of staphylococcal biofilm-associated infection. However, such a factor very likely does not exist, because staphylococcal biofilm formation, as we now know, is multifactorial. Still, targeting the biosynthesis of a factor that appears to be involved in at least the majority of staphylococcal biofilm-associated infection, such as PIA, seems worth considering. Interestingly, some bacteria produce a PIA-degrading enzyme, which - although not present in staphy-lococci - can degrade staphylococcal PIA and destroy staphylococcal biofilms (Kaplan et al. 2004a). This PIAse, named dispersin B, has first been found in Actinobacillus actinomycetemcomitans and appears to have potential as an anti-biofilm drug (Kaplan et al. 2003). Similarly, although not biofilm-specific, the pep-tidoglycan-degrading enzyme lysostaphin is being evaluated for therapeutic use against biofilm-forming...

Culture Based Methods Dedicated to MRSA Identification

Liquid cultures have been instrumental to the nascent field of microbiology and are still used routinely in laboratories to recover minute amounts of bacteria or are employed as backup media. For example, Mueller-Hinton supplemented by oxacillin is still currently used to detect or confirm presence of MRSA from swabs sampled for surveillance programs. This medium appears in the guidelines for the prevention and control of antibiotic-resistant organism from the NCCLS recommendations (NCCLS,2002). However, solid media are now commonly used for organism isolation and identification, allowing MRSA identification in approximately 24 h. Agar plates provide numerous advantages, such as the possibility for microbiologists to detect the presence of relevant colony morphologies, isolate them by sub-plating, and assess their purity on isolation plates. Pure isolates are essential for further phenotypic testing, including speciation (when required), antimicrobial susceptibility testing, and...

Impact of Recent Hybridization Technologies on the Identification of MRSA

Oligonucleotides able to hybridize with complementary target sequences. PCR-amplified products are detectable with low-density oligoarrays, enabling the parallel detection of several targets during the same experiment. The basic principle of DNA probe technology is hybridization, relying on denaturation of double-stranded DNA and detection of hybridized labeled-DNA. Recent reports relying on ribosomal or other specific markers demonstrated the identification of Staphylococcus at the species level (Hamels et al., 2001 Couzinet et al., 2005a) and even provided an overview of the virulence factors harbored by clinical isolates during the same experiment (Saunders et al., 2004 Couzinet et al., 2005b).

Risk Assessment for MRSA at Hospital Admission

Although previously considered a purely nosocomial pathogen, recovered from hospitalized patients only, MRSA is now being recovered with increasing frequency at hospital admission (Eveillard etal. 2002, Huang etal. 2002, Tacconelli et al. 2004a). In an outpatient military clinic, MRSA colonization was present in 2 of screened patients with a tendency to be more frequent in men, those who were older, or with previous hospitalizations (Kenner et al. 2003). These community-acquired MRSA strains arise from two different patient populations those with true community-acquired MRSA strains which have emerged de novo from community-based S. aureus strains in specific populations as in children, inmates, and military personnel, and health care-associated strains which have been acquired in the hospital during a recent exposure to a health care setting or surgical procedures (Charlebois et al. 2002, Weber 2005). A meta-analysis of MRSA infections identified within 24-72 hours of...

Grampositive Resistant Organisms Mrsa And

The acquisition of the staphylococcal cassette chromosome mec by a sensitive strain confers resistance to methicillin (and all beta-lactams currently marketed) (132). Exceptions to this include certain beta-lactams that target penicillin-binding protein 2a such as 2 cephalosporins in development (ceftaroline and ceftobiprole) and an early investigational carbapenem. Epidemiologic evidence suggests that the spread of MRSA has been due to a few clonal types, introduced into a population by infected or colonized patients, rather than the frequent de novo development of new MRSA clones (132-138). Interrupting transmission is an appropriate strategy in controlling this type of spread (43). Antimicrobials exert selective pressure that favors the growth of acquired VRE strains in the stool, making transmission more likely (42). The colonization pressure of VRE in a given unit is a strong predictor of VRE acquisition, and the effect of selective pressure exerted by antimicrobials may be...

Risk Assessment for MRSA During Hospitalization

Epidemiology of nosocomial acquisition of MRSA is well described in numerous reports (Grundmann et al. 2002, Graffunder and Venezia 2002, Campbell et al. 2003). Risk factors include underlying disease, prior hospitalization, prior antimicrobial use, prior surgery, length of hospitalization, central venous catheterization and endotracheal intubation, enteral feeding, admission to ICU, nursing staff work load, and compliance with hand disinfection procedures (Grundmann et al. 2002, Graffunder and Venezia 2002, Campbell et al. 2003). Specific analysis of antibiotic exposure showed that quinolones (i.e., levofloxacin and ciprofloxacin) and macrolides were associated with MRSA but not with MSSA isolation (Graffunder and Venezia 2002, Weber et al. 2003). A 1-year study carried out at an ICU in a U.K. university hospital showed, using a multivariate model, that urgent admission, value of APACHE II score at 24 hours, bronchoscopy, and days of staff deficit were all independent risk factors...

Interventions for the Control of MRSA and VRE

Both VRE and MRSA can survive on the hands of healthcare workers, and persistence on environmental surfaces can be a source of contamination of healthcare workers' hands and gloves (44,45,145). Proximity to patients Some transmission of DROs is probably the result of contamination of healthcare workers' clothing. While the efficacy of gowns is not entirely clear, they have been shown to reduce transmission of VRE and MRSA, and most studies appear to support their utility (43). Slaughter et al. could not demonstrate that gowns added additional benefit over gloving, whereas Puzniak and colleagues demonstrated a beneficial effect of gowns in reducing VRE transmission in a medical ICU when colonization pressure was high (60,146). The utility of masks has not been established for preventing the transmission of MRSA. Because of potential airborne transmission of staphylococci, nasal colonization, and shedding of staphylococci by patients and healthcare workers, there is, at...

Risk Assessment for Mortality Caused by MRSA

The debate about the risk of excess mortality caused by MRSA is still open. The majority of the studies demonstrated that MRSA infections are significantly associated with longer hospitalization, more days of antibiotic treatment, and higher costs when compared to MSSA infections (Osmon et al. 2004, Cosgrove et al. 2005). In a cohort study of 348 patients with MRSA (96 patients) or MSSA bacteremia (252 patients) methicillin resistance was associated with significant increases in length of hospitalization and hospital charges. MRSA bacteremia had a median attributable duration of hospitalization of 2 days and a median attributable hospital charge of 6916 dollars (Cosgrove et al. 2005). In a prospective cohort study, Melzer and colleagues (2003) observed that patients with MRSA bacteremia were older and had more frequent ICU admissions and wounds. After adjusting for confounders (except for the appropriateness of initial empirical antibiotic therapy), attributable mortality was...

What Do We Do with Methicillin Resistant Staphylococcus aureus in Surgery

Methicillin-resistant Staphylococcus aureus (MRSA) is typical of the burden of antimicrobial resistance in nosocomial infections. S. aureus is one of the most frequent nosocomial pathogens, and the prevalence of methicillin resistance has been constantly rising among S. aureus strains over the last four decades. This has been responsible for an increase in length of hospital stay, treatment-related complications, costs, and, in some instances, attributable mortality. Because MRSA, like methicillin-susceptible S. aureus (MSSA), frequently colonizes the skin, it is of particular concern as a cause of infection in surgical patients. However, the antibiotics commonly recommended for perioperative prophylaxis do not target MRSA. Therefore, one can legitimately wonder if current preventive measures are still sufficient.

Epidemiology of MRSA Trends Relevant to Surgical Patients

Methicillin-resistant strains of S. aureus were first isolated in the 1960s, shortly after the introduction of methicillin (Jevons et al. 1963). In the 1970s and 1980s, the epidemiology of MRSA infections was characterized by small outbreaks that could be controlled by standard measures. A decade later, strains emerged that became endemic in many hospitals. Methicillin resistance is characterized by wide geographical variations. In Europe, the prevalence of resistance to methicillin in S. aureus isolated from blood varies almost 100-fold, from < 1 in northern countries to > 40 in southern and western countries (The European Antimicrobial Resistance Surveillance System EARSS 2004). In addition, this prevalence differs notably among hospitals within countries, the highest variance being observed in countries with a prevalence of 5 to 20 (Tiemersma et al. 2004). In the United States, MRSA accounted for nearly 60 of nosocomial S. aureus infections acquired in intensive care units in...

Physiopathology of MRSA Infections in Surgical Patients

MRSA and MSSA infections share common pathogenic mechanisms. Although asymptomatic nasal colonization with S. aureus is common, it appears to be an important factor in the development of most infections due to this organism (vonEiff etal. 2001). Conflicting results have been published on risk factors for nasal carriage in patients. In the context of a clinical trial evaluating whether mupirocin prevented surgical site infections due to S. aureus, Herwaldt et al. prospectively collected data on 70 characteristics in a population of 4030 patients before surgery. Twenty-two percent of these patients carried S. aureus in their nares the proportion of MRSA was not specified. Independent risk factors for S. aureus nasal carriage were obesity, male gender, and a history of cerebrovascular accident (Herwaldt et al. 2004).

Burden of MRSA Infection in Surgical Patients

The burden of MRSA infection can be inferred from two distinct perspectives. Some studies describe it as a part of all S. aureus infections. Their results are instructive but poorly generalizable because this part varies from one hospital to the other. Other studies describe the burden of MRSA through comparison with MSSA. S. aureus has consistently been reported as the most frequent cause of infections at surgical sites (Jernigan 2004). According to NNISS data, for instance, 30.9 of SSIs following CABG, cholecystectomy, colectomy, and total hip replacement were due to S. aureus the proportion of S. aureus infections attributable to MRSA increased from 9.2 in 1992 to 49.3 in 2002 (Anonymous 2004). In another study, S. aureus accounted for 49 of sternal SSI developing after CABG (Sharma et al. 2004). Thirty-six percent of these S. aureus were MRSA. Bacteremia was noted in 31.4 of patients with sternal SSI, and all were due to S. aureus. The most devastating infectious complication of...

Systemic Perioperative Prophylaxis with Antibiotic Active Against MRSA

The impact of perioperative antibiotic prophylaxis on SSI due to staphylococci has been mainly studied in patients undergoing cardiac surgery. SSI is indeed a frequent complication of cardiac surgery. The most severe SSIs, deep sternal wound infection and mediastinitis, occur in 0.25 to 2 of the patients. They often require reoperation and prolonged antibiotic therapy, and are associated with mortality rates of up to 30 . Guidelines typically recommend antibiotic prophylaxis with a first- or second-generation cephalosporin, based on many clinical studies conducted before the 1990s that have been summarized in a meta-analysis published in 1992 (Kreter and Woods 1992). The use of a cephalosporin is frequently challenged because of the escalating prevalence of resistance to methicillin in Gram-positive cocci that are responsible for SSI after cardiac surgery. S. aureus and coagulase-negative staphylococci indeed account for 34-54 and 12-44 of these infections, respectively (Borger et al....

Treatment of MRSA Infections

The therapeutic approach to patients with MRSA infection depends on the site of infection and the in vitro susceptibility pattern of the infecting strain. The site of infection, and the removal of an infected device or drainage of an abscess, are often more important than antimicrobial therapy, as is the case for all staphylo-coccal infections. Superficial infections often do not require systemic antimicrobial treatment. The emergence of MRSA infections in the community also places emphasis on the importance of nonantibiotic management of localized infections. Although sometimes neglected, appropriate drainage is the optimal management of many skin and soft tissue infections. Antibiotic therapy is merely an adjunct in deeper, closed-space infections. Cutaneous abscesses typically resolve with proper drainage and or debridement alone, and collections left without drainage in the setting of antibiotic treatment promote the emergence of resistance. The current drug of choice for serious...

The Epidemiology of MRSA

S. aureus is a human commensal, colonizing predominantly the anterior nares of approximately 30 of the general population, with subgroups such as insulin-dependent diabetes mellitus, or dialysis-dependent renal failure having higher carriage rates (Kluytmans et al. 1997). Risk factors for MRSA colonization and infection change over time and with the evaluated population identified risk factors vary depending on whether patients with MRSA infection or colonization were studied and vary by geographical location and demographic characteristics of the patient population. Numerous studies have looked at risk factors for MRSA colonization and infection, both at admission and during hospitalization. Risk factors that have been described for hospital acquisition of MRSA include antimicrobial exposure, length of stay in the hospital or intensive care unit, colonization pressure, and illness severity. Risks for colonization or infection at admission have included previous hospitalization,...

Genome Comparisons of Diverse Staphylococcus aureus Strains

As with other pathogens, the genome of Staphylococcus aureus can be subdivided into core and accessory segments, comprising roughly 75 and 25 of the genome. Particular attention is given to the MRSA252 strain, which is phylogenetically distinct from other S. aureus genomes, is epidemic in the United Kingdom and North America, and is closely related to methicillin-susceptible clinical isolates that are hypervirulent in musculoskeletal infection models. This strain contains a number of unique or unusual small-scale variations compared with other genomes, and their potential significance as mediators of virulence is discussed. With respect to horizontally transferred virulence determinants of the core genome, another focus is to assess the integration sites of toxin-carrying prophage, in terms of a potential cost-benefit relationship. The Staphylococcal Cassette Chromosome is discussed in terms of its role in promoting the evolution of antibiotic resistance, and as a potential mediator...

Healthcare Associated MRSA

Most nosocomial MRSA is multidrug resistant. They tend to colonize and infect patients during hospitalization or stays in long-term care facilities, after surgery or after contact with persons who had an MRSA infection or used illicit drugs. In the 1970s, periodic outbreaks were described in various parts of the world, in association with high levels of oxacillin or methicillin use and in intensive care environments, but since the 1980s, MRSA became a significant worldwide problem, first in large hospitals and later in smaller community hospitals. Nosocomial MRSA is a growing problem in the region. Information gathered in the PAHO-sponsored program of nosocomial infections (PAHO 2006), reported for the year 2004, country MRSA prevalence as follows Argentina 42.5 of 5851 isolates, Bolivia 36 of 1167, Chile 80 of 246, Colombia 47 of 4214, Costa Rica 58 of 674, Cuba 6 of 80, Ecuador 25 of 1363, Guatemala 64 of 1483, Honduras 125 of 393, Mexico 52 of 497, Nicaragua 20 of 296, Paraguay 44...

The Molecular Basis of Biofilm Formation in Staphylococci

Biofilm Formation

Fig. 1 Phases of biofilm development in staphylococci. Biofilms form by initial attachment to a surface, which can occur on tissues or after covering of an abiotic surface by host matrix proteins in the human body (specific, protein-protein interaction) or directly to an abiotic surface (nonspecific). Subsequently, biofilms grow and mature. The molecules that connect the cells in a staphy-lococcal biofilm are predominantly the exopolysaccharide PIA, teichoic acids, and some proteins such as the accumulation-associated protein Aap. Finally, cell clusters detach. Detachment is facilitated by expression of the surfactant-like PSM peptides, which are also important in producing the three-dimensional structure of the biofilm. During infection, attachment is a crucial part of the colonization on host tissues or on indwelling medical devices, whereas detachment is a prerequisite for the dissemination of an infection Fig. 1 Phases of biofilm development in staphylococci. Biofilms form by...

Mechanism of Resistance and Molecular Background of HAMRSA

Resistance to methicillin confers resistance to all beta-lactam antibiotics and requires the presence of the mecA gene, encoding the production of PBP 2a (Chambers 1997). The origin of the mec element is not known. The assembly of the several mec element structures that have been found may have evolved from multiple hosts, possibly among coagulase-negative staphylococci. PBP 2a is a transpeptidase that catalyzes the formation of cross-bridges in bacterial cell wall peptidoglycan, and has a low affinity for all p-lactam antibiotics. It takes over the function of cell wall biosynthesis in the presence of p-lactam antibiotics when normally occurring PBPs are inactivated by ligating p-lactams. The mecA gene is carried on a mobile genetic element known as the staphylococcal cassette chromosome (SCC) mec. Besides the mecA gene itself, the SCCmec element contains regulatory genes, an insertion sequence element, and a unique cassette of recom-binase genes responsible for the integration and...

Autophagy in Staphylococcus aureus Infection

A substantial increase in resistance to antimicrobial agents among bacterial pathogens has been found, particularly in Gram-positive bacteria this compromises traditional therapies (Finch 2006). Staphylococcus aureus, one of the most ubiquitous Gram-positive pathogens, is a major cause of infections in both hospitals and care centers, and has exhibited significant resistance to methicillin (methicillin-resistant S. aureus, MRSA) (Kollef and Micek 2006). MRSA is generally considered to be a nosocomial pathogen that is associated with higher levels of morbidity and mortality as compared to other diseases caused by pathogens susceptible to methicillin. The prevalence of MRSA is increasing significantly in many parts of the world, with resistance rates of greater than 50 in the United States (Wisplinghoff et al. 2004) and some European countries (EARSS Management Team 2006). Like GAS, S. aureus was previously thought to be an extracellular bacterium however, the adhesion and invasion of...

Inducible Clindamycin Resistance in Staphylococci and Streptococci

Some staphylococcal and streptococcal strains that are resistant to erythromycin and susceptible to clindamycin may have inducible clindamycin resistance, referred to as macrolide-lincosamide-streptogramin B (MLSB) resistance, due to the presence of erythromycin ribosomal methylase erm(A) or erm(B) (Hamilton-Miller and Shah, 2000). This family of enzymes methylates the N-amino group of adenine residue 2058 in 23S rRNA, which prevents access of the antimicrobial to its binding site on the ribosome. The resistance is referred to as macrolide-lincosamide-streptogramin resistance, as it affects the activities of all three drug groups (Eady et al., 1993 Siberry et al., 2003). The second mechanism that produces macrolide resistance in staphylococci is mediated by msr(A) gene. The gene encodes an ATP-dependent efflux pump that only confers resistance to macrolides and streptogramin B but not to lincosamide, such as clindamycin (Eady et al., 1993 Siberry et al., 2003). Although some strains...

Methicillin Resistance in Staphylococci

Methicillin resistance in clinical isolated staphylococci is mostly mediated through acquisition of mecA gene encoding a mutant penicillin binding protein (PBP)2a by bacterial genome. PBPs are the enzymes that catalyze the reaction that crosslinks the peptidoglycan of the bacterial cell wall. Binding of PBP to (-lactam antimicrobials inhibits the enzyme activity and prevents bacteria growth by interfering with cell wall formation. In contrast to the PBPs in methicillin-susceptible strains, which have high affinity for most (-lactam antimicrobials, PBP2a has low affinity for binding ( -lactams. In methicillin-resistant strains, the essential function of PBP is undertaken by PBP2a to maintain survival of the bacterium in the presence of antimicrobials (Chambers, 2003). Heterogeneity is an important feature of methicillin-resistant staphylococci. The level of resistance varies according Due to the heterogeneous nature of the methicillin resistance, testing of the presence of mecA gene by...

Box 124 MRSA and a Beauty Salon

In late 2004, a beautician in Holland experienced recurring infection with MRSA that required surgical drainage. After antibiotic treatment, she was declared MRSA-free (December 2005), but 3 months later, she tested positive for colonization. An epidemiologic study was performed that included 45 persons she contacted between July 2005 and December 2006. Fifteen persons had skin infections, and 10 of these individuals were colonized with MRSA. Overall, 11 persons were MRSA-positive, each with the USA300 strain. Two salon customers had skin lesions caused by MRSA one was hospitalized. Waxing to remove unwanted hair was suspected as a route of bacterial transmission, but screening of 19 regular customers, employees, and waxing implements was negative.258 Thus, waxing may not contribute frequently to transmission of MRSA. When a person is infected with MRSA, infections can recur, probably from bacterial colonization of the patient's body. (Persons with hospital infections are often...

General Costs Of Mrsa

Most authorities would agree that MRSA is probably the most important resistant bacterium associated with HAI. Staphylococci themselves are the most common pathogens causing bacteraemia according to national surveillance of bloodstream infections (Pfaller et al., 1998). Along with Escherichia coli, they account for over 55 of all bacteraemias from one recent study (Diekema et al., 2000). The only major change from similar previous studies was the increase in methicillin (oxacillin) resistance in both coagulase negative staphylococci and S. aureus (Diekema et al., 2000 Pfaller et al., 1998 Schaberg et al., 1991). S. aureus was the most common pathogen referred to the SENTRY Antimicrobial Surveillance Program from 1997 to 1999, where it was found to be the most prevalent bloodstream infection, skin and soft tissue infection, and cause of pneumonia in all geographic areas studied (Diekema et al., MRSA does not appear to replace MSSA in the overall burden of infection, as the attack rate...

Staphylococcus aureus with Decreased Susceptibility to Vancomycin

Clinical emergence of vancomycin intermediate or resistant S. aureus has been reported, even though the prevalence of the strains with reduced vancomycin susceptibility is still low (Srinivasan et al., 2002 Liu and Chambers, 2003). Although the molecular mechanism of the intermediate resistance in staphylococci is not yet established, studies have suggested that a novel mechanism that differs from the one used by enterococci are employed by staphylococci (Walsh and Howe, 2002) Currently, CLSI defines staphylococci with vancomycin MIC of < 4 Mg mL as susceptible, isolates with MIC of vancomycin 8 16 Mg mL as intermediate, and isolates with vancomycin MIC of > 32 Mg mL as resistant. Accordingly, VISA and VRSA refer to S. aureus with a vancomycin MIC of 8-16 Mg mL and a MIC of > 32 Mg mL, respectively. Detection of VISA requires MIC methods with 24 h incubation. Disk diffusion tests with the standard 30 Mg vancomycin disk have been shown to have low sensitivity (Tenover et al.,...

Community Acquired Methicillin Resistant Staphylococcus aureus CAMRSA

Community-acquired MRSA infection (CAMRSA) emerged during the last decade and causes considerable morbidity and mortality. Like nosocomial MRSA infection, clonal spreading of CAMRSA between community and hospital has been noted (Boucher and Corey 2008). The isolates of sequence type (ST59) identified by the multilocus sequence typing (MLST) method appeared to be the major clone of CAMRSA in northern Taiwan, accounting for more than 90 of CAMRSA (Boyle-Vavra et al. 2005). In Hong Kong, three MLST types of CAMRSA have been identified ST30-IV (the more common), ST59-V, and ST8-IVA, exhibiting a diverse genetic distribution (Ho et al. 2007). In Japan, CAMRSA was found in 10-17 of S. aureus isolates from bullous impetigo and could be divided into three sequence types ST89 (66.7 ), ST8 (20 ), and ST91 (13.1 ) (Takizawa et al. 2005). An increasing incidence of CAMRSA-related soft tissue infection in Singapore has been reported with a predominant ST30 strain (Hsu et al. 2006). In Korea,...

Physiology of Staphylococcal Biofilms Lessons from Transcriptional Profiling

After complete genome sequences of S. aureus, S. epidermidis, and other staphylococci had become available, transcriptional profiling of biofilm gene expression was soon initiated. Three transcriptional profiling-based manuscripts have been published, two on S. aureus (Beenken et al. 2004 Resch et al. 2005) and one on S. epidermidis (Yao et al. 2005), and in addition, proteomics were used to confirm results obtained by the microarray experiments (Resch et al. 2006). The general lessons learned from these studies are comparable, although differences exist that originate most likely from different experimental setups. In addition, it has to be taken into consideration that two studies (Resch et al. 2005, 2006) were conducted in the SA113 strain of S. aureus, which is a natural agr mutant. First and foremost, staphylococcal biofilms have a physiological status that is characterized by a general downregulation of active cell processes, such as protein, DNA, and cell wall biosynthesis,...

Molecular Methods for MRSA Identification

Rapid detection of MRSA by standard clinical microbiological procedures appears then tedious and time consuming, as it first requires identification of isolated S. aureus colonies from mixed flora samples before assessing their antibiotic susceptibility profile. Direct or indirect particle agglutination assays using antibody-coated beads offer a rapid alternative to oxacillin susceptibility testing. For example, MRSA-Screen (Denka Seiken, Tokyo, Japan) provides sensitive and specific immuno-detection of MRSA in a pure culture by using anti-PBP2' antibody-coated latex beads, and reveals similar to standard oxacillin disk diffusion or oxacillin salt agar screening (Cavassini et al., 1999 Hussain et al., 2000). However, the specific immuno-detection of MRSA based on PBP2' cannot be performed in the presence of other methicillin-resistant staphylococcal species, organisms that are frequently recovered as commensal contaminant of mixed flora samples (Cavassini et al., 1999). Indeed, the...

Risk Factors for MRSA Infection in Surgical Patients

The main and most frequently reported risk factors for colonization with or infection by MRSA in all hospitalized patients include a history of previous MRSA colonization or infection, previous hospital stay, the length of the current hospital stay, the presence of invasive devices, previous antibiotic treatments, contact with a roommate who carries MRSA, chronic skin ulcers, and diabetes mellitus (Graffunder and Venezi 2002, Tacconelli et al. 2004, Troillet et al. 1998). In addition, belonging to specific patient populations (e.g. intravenous drug users, nursing home residents) may be predictive of MRSA carriage in some regions as a consequence of local epidemic situations. Dodds Ashley et al. undertook a case-control study comparing 64 patients who developed an MRSA mediastinitis after a median sternotomy to 79 patients with mediastinitis due to MSSA and 80 uninfected control patients (Dodds Ashley et al. 2004). In a multivariate analysis, patients who were diabetic, female, and >...

Preoperative Use of Topical Antibiotics Active Against MRSA

The impact of topical antibiotic for eradication of MSSA and or MRSA is best known for mupirocin, a compound synthesized by Pseudomonas fluorescens that inhibits bacterial protein synthesis by reversibly binding to bacterial isoleucyl-tRNA synthetase. Several studies have demonstrated the efficacy of mupirocin for the eradication of MRSA and MSSA in different populations (Laupland and Colby 2003). Its effect in healthy healthcare workers (Doebbeling et al. 1993, Fernandez et al. 1995, Reagan et al. 1991, Scully et al. 1992) may be particularly relevant for prevention in surgical patients. By pooling six double-blind, randomized studies in 339 healthcare workers who carried S. aureus in their nose, Doebbeling et al. reported that the application of mupirocin twice daily for 5 days eradicated 91 of participants, compared with 6 of those who received a placebo. No emergence of resistance to mupirocin was observed (Doebbeling et al. 1993). Early studies in the surgical setting were...

MRSA Is Putting Resistance in the News

MRSA is the acronym for methicillin-resistant Staphylococcus aureus. (Acronyms are usually pronounced letter by letter, as in DNA scientific names are always italicized after an initial spelling of the entire name, the first name is often abbreviated by its first letter.) S. aureus is a small, sphere-shaped bacterium (see Figure 1-1) that causes skin boils, life-threatening pneumonia, and almost untreatable bone infections. It often spreads by skin-to-skin contact, shared personal items, and shared surfaces, such as locker-room benches. When the microbe encounters a break in the skin, it grows and releases toxins. Figure 1-1 Staphylococcus aureus. Scanning electron micrograph of many MRSA cells at a magnification of 9,560 times. Figure 1-1 Staphylococcus aureus. Scanning electron micrograph of many MRSA cells at a magnification of 9,560 times. Sixty years ago, S. aureus was very susceptible to many antibiotics, including penicillin. Susceptibility disappeared, and the pharmaceutical...

Other Staphylococci

Similar to S. epidermidis, most other staphylococci have a benign relationship with their host and develop from commensals to pathogens only after damage of a natural barrier such as the skin. In comparison with S. epidermidis and S. aureus, biofilm-associated infections with other staphylococci are far less frequent. It is not known if this is due to a difference in virulence or abundance on the human skin, or - which appears most likely - a combination of both factors. CoNS found in humans colonize different parts of the human skin and mucous membranes, with each species having a certain predominance on specific parts of the body (Kloos and Schleifer 1986). Notably, every species of CoNS that has been characterized as a resident of the human body (S. epidermidis, S. capitis, S. hominis, S. haemolyticus, S. saccharolyticus, S. warneri, S. lugdunensis, S. saprophyticus, S. cohnii) has also at least once been connected to an infection. The specific sites and frequency of infection seem...

Boils and Carbuncles

A boil is a collection of pus beneath the top layer of skin. It is caused by bacterial infection of a hair follicle, the tiny pit in the surface of the skin in which a hair grows. Boils can cluster under the skin such a cluster is known as a carbuncle. Boils may result from infection of a cut or scrape in the skin, poor hygiene, cosmetics that clog the pores, exposure to chemicals, and friction from tight clothing or shoes. Perspiration contributes to the development of boils and carbuncles and can make them worse. Boils and carbuncles usually appear on the scalp, beard area of the face, arms, legs, underarms, and buttocks. pus onto the surface of the skin. Carbuncles discharge their contents through a Skin and number of openings in the surface of the skin. Once they have ruptured, boils Hair and carbuncles are less painful, but inflammation may persist for a few days or weeks. Scarring occurs in most cases. You may be able to detect a boil on your own. Avoid squeezing or piercing a...

Interpretation of Significance

Several common blood isolates are almost always significant Staphylococcus aureus, Escherichia coli, and other members of the family Enterobacteriaceae, Pseudomonas aeruginosa, and Candida albicans. In contrast, common skin organisms, such as coagulase-negative staphylococci (CoNS), Coryneform bacilli, alpha-hemolytic streptococci, and Propionibacterium acne, are frequent contaminants. However, with many patients carrying an intravascular device that is prone to colonization and infection, each positive culture entails clinical correlation with other findings and sound judgment to make final assessment (Mirrett et al., 2001 Weinstein, 2003).

Aspects of Virulence Quorum Sensing

Quorum-sensing mechanisms in S. aureus differ from those already described but achieve similar objectives (Ji, Beavis and Novick 1995). Many staphylococcal virulence factors are regulated by the agr group of genes, which allow the transcription of genes responsible for encoding a variety of toxins. It is conceivable that staphylococci originally concentrate their genetic expression on adherence at a primary site before quorum-sensing molecules signal that the required growth density has been achieved. Thereafter, a genetic switch is triggered in order to activate the agr locus and thus secretion of known virulence determinants such as a-toxin, p-toxin, and 8-toxin (Recse et al. 1986).

Aspects of Virulence Horizontal Transfer of Virulence and Resistance Genes

P-Lactam antibiotics such as penicillin, ampicillin, cloxacillin, and ceftriaxone, induce the SOS response in S. aureus this results in promotion of replication and high-frequency horizontal transfer of pathogenicity island-encoded virulence factors (Maiques et al. 2006). These pathogenicity islands carry genes for virulence determinants such as TSST, other superantigenic toxins, and biofilm promoters. Fluoroquinolones and trimethoprim have also been implicated in similar SOS induction in staphylococci (Goerke, Koller and Wolz 2006). In addition, fluoro-quinolones induce an SOS response in E. coli, which results in horizontal transfer of bacteriophages encoding a Shiga-like toxin (Zhang et al. 2000). It appears that nonlethal use of many antibiotics can induce the SOS response and potentially enhance the transmission not only of resistance, but of virulence factors as well. Since MRSA continues to increase in hospitals, there is concern that heterogeneous populations of S. aureus will...

Aspects of Virulence Bacterial Adhesion

And orthopedic devices during the early stages of infection. It has been shown that subinhibitory concentrations of antibiotics can affect staphylococcal binding to fibrinogen and collagen (Proctor, Olbrantz and Mosher 1983, Butcher et al. 1994). Exposure of highly fluoroquinolone-resistant S. aureus to subinhibitory levels of ciprofloxacin significantly increases the expression of fibronectin adhesins. This leads to increased attachment of the bacterial cells to immobilized fibronectin in an in vitro model (Bisognano et al. 1997). Increased adhesion also occurs with other strains of staphylococci, including MRSA and methicillin-susceptible S. aureus. Indeed, staphylococcal expression of surface adhesins is altered following the acquisition of the methicillin resistance element mecA (Vaudaux et al. 1998). It is tempting to hypothesize that this antibiotic-promoted increase in adhesion might contribute towards the emergence of staphylococci expressing increased levels of antibiotic...

Pathogen Persistence Biofilms

It is known that bacteria in biofilms are more resistant to treatment with antimicrobial agents than the corresponding free-living or planktonic cells (Donlan 2002). Drug-resistant E. coli biofims have been shown to exhibit p-lactamase activity, enhancing resistance to antibiotics such as imipenem and cefoxitin (He, Li and Li 2001). Small-colony variants of staphylococci within biofilms may be highly resistant to the bactericidal action of oxacillin or vancomycin (Chuard et al. 1997). It appears that a fraction of cells within a biofilm population will always exhibit a resistant phenotype (Meyer 2003) these bacteria are often termed persister cells (Keren et al. 2004). Studies have suggested that persisters are neither defective cells nor cells created in response to antibiotics, but are rather specialized survivor cells. Keren et al. (2004) showed that tolerance of E. coli to ampicillin and ofloxacin is due to persister cells.

Aspects of Virulence Antibiotic Resistance

MRSA isolates obtained after clinical failure of vancomycin demonstrate physiological changes when compared with the original parent strain (Sakoulas et al. 2006). Analysis of the virulence regulatory group of agr genes from the initial bloodstream isolate showed little 8-hemolysin activity. After 9 months of vancomycin and a switch to linezolid, however, 8-hemolysin expression increased noticeably. There was also a decrease in autolysis, reduced killing by vancomycin in vivo, and increased biofilm formation in isolates obtained after prolonged exposure to vancomycin (Sakoulas et al. 2006). It has already been suggested that there is a link between pathogenicity and vancomycin tolerance in MRSA, since the discovery that the agr group of genes are implicated in the expression of penicillin-binding proteins that help establish the VISA phenotype (Schrader-Fischer and Berger-Bachi 2001). Staphylococcal resistance contributes toward the pathogenesis of wound infections. Resistant...

Epidemiologic Evidence That Influenza Increases the Risk of Bacterial CAP

With respect to CAP caused by S. aureus, Hageman recently reported 17 cases of culture-confirmed community-acquired S. aureus pneumonia among persons with either an influenza-like illness (i.e. fever plus sore throat or cough) or laboratory-confirmed influenza infection before onset of pneumonia symptoms 35 . Of the 13 cases from whom S. aureus isolates were available, 11 were methicillin resistant and 10 of these were identified as the USA300 strain, a pulsed-field gel electrophoresis type associated with severe necrotizing pneumonia 54 .

VITEK1 and VITEK 2 Systems

Sulbactam-Enterobacter spp., ampicillin sulbactam-Serratia spp., aztreonam-Pseudomonas spp., imipenem-Proteus spp., meropenem-Acinetobacter spp., piperacillin-Acinetobacter spp., piperacillin tazobactam-Acinetobacter spp., linezolid-Enterococcus spp., for resistance and linezolid-Staphylococcus spp for resistance. Alternative methods have to be used for testing these drug-organism combinations.

Bringing Evidence Based Medicine to Clinicians

Then individual relevant randomized trials. In a different example, a physician might ask whether early valve replacement will improve the outcome of a patient with Staphylococcus aureus endocarditis. In this case the briefest answer might be found in a narrative review and evidence can be shown in more detail from prospective and then retrospective observational studies.

Gen Probe Direct Nucleic Acid Detection Method

Staphylococcus auresus probes are available for Campylobacter, Enterococcus, Group A Streptococcus (Streptococcus pyogenes), Group B Streptococcus (Streptococcus agalactiae), Haemophilus influenzae, Neisseria gonorrhoeae, Staphylococcus aureus, Listeria monocytogenes, and Streptococcus pneumoniae. The advantage of these assays is they are nonisotopic, simple to use, and have high sensitivity (ranging from 92 to 100 ) and specificity (ranging from 99 to 100 ) (see Table 8.1).

Application to Gram Positive Bacteria

PFGE is considered the accepted standard for molecular typing of nosocomial pathogens such as Staphylococcus aureus and vancomycin-resistant enterococci (VRE). Nasal carriage of S. aureus occurs in 20-60 of the general population, and methicillin-resistant S. aureus (MRSA) pose a particular risk for nosocomial transmission (Kluytmans et al., 1997). It is clear that MRSA can be transferred between patients in the hospital setting and cause nosocomial infections. Rapidly assessing the clonal relatedness of these isolates is critical in determining the extent of transmission during an outbreak and in measuring the strategies for its containment. PFGE is often used to examine the genetic identity of MRSA isolates. In a recent publication from our medical center, PFGE results showed that vertical transmission of one clone of MRSA occurred from a mother to her preterm infants, followed by horizontal spread to other infants in the same neonatal intensive care unit (Morel et al., 2002). We...

Interpretation and Limitations of Data

Multiple individuals derive data from multiple sources, so there is a potential danger of transcription error, which can be minimized by suitable training. Data, critical for a prescribing decision, may also be missing (unrecorded), e.g., phone call advice from an infection specialist or not included in the data set being collected, e.g., MRSA carriage in a patient with a soft tissue infection treated with vancomycin. Prescribing surveys could certainly be enhanced if microbiological data could be linked directly to the data set.

Probe Amplification Systems

Another similar system, cycling probe technology, uses a unique chimeric DNA-RNA-DNA probe sequence that provides an RNase H sensitive scissile link when hybridized to a complementary target DNA sequence (Duck et al., 1990). The CPT reaction occurs at a constant temperature, which allows the probe to anneal to the target DNA. RNase H cuts the RNA portion of the probes, allowing the cleaved fragments to dissociate from the target DNA. A cycling probe has been designed for detection of a specific sequence with the mecA and vanA B genes, and the former one has been cleared by the Food and Drug Administration for in vitro diagnostic use as a culture confirmation assay for methicillin-resistant Staphylococcus au-reus (Beggs et al., 1996 Cloney et al., 1999 Fong et al., 2000 Modrusan et al., 2000).

Isolation Precautions

Many studies have shown that in the setting of multiple (simultaneous or sequential) interventions, implementation of surveillance cultures to identify colonized patients has led to a significant reduction in rates of colonization and infection of patients with MRSA or VRE. One study compared the rate of transmission of MRSA from colonized patients who were identified by active surveillance and placed in contact precaution with that from patients who were colonized but not yet identified or isolated. The rate of transmission was 15.6-fold higher for patients not identified to be colonized and for whom standard precautions were being used 21 . microbiological cultures from infections has been demonstrated in a hospital with an MRSA outbreak. A clonal outbreak of MRSA in a hospital was the cause of 40 of all hospital-acquired S. aureus bloodstream infections and 49 of all S. aureus surgical-site infections. During the first 3 years of the outbreak, patients with MRSA were identified for...

Prevention of Infection to Prevent Resistance

The application of infection control measures to prevent spread of resistant organisms may never be perfect, and even when control of resistance is nearly perfect there has been a striking lack of correlation of resistance and overall nosocomial infection rates. For example, those countries which have used active surveillance to almost eliminate MRSA have overall nosocomial infection rates similar to those of the United States, where MRSA is often rampant. This suggests that greater emphasis should be placed on prevention of infection, specifically related to devices.

Antimicrobial Resistance in the Community and Hospitals

The resistance problem is particularly serious in the hospital environment, where the selection pressure caused by massive antimicrobial use, combined with epidemic spread of selected strains, is responsible for the emergence of multidrug-resistant (MDR) microorganisms such as methicillin-resistant S. aureus (MRSA), vancomycin-resistant Enterococcus species (VRE), Pseudomonas aeruginosa, and Acinebacter baumannii.5-9 According to the Centers for Disease Control and Prevention (CDC), more than 70 of bacteria now causing hospital acquired infections are resistant to at least one of the drugs that are most commonly used to treat them.10 Especially the intensive care units (ICUs) contribute to nosocomial infections through catheter-related bloodstream infections, ventilator-associated pneumonias (VAP), and surgical site infections. Prevention of development of MDR pathogens should be the main goal of antimicrobial policy of ICUs, and adherence to preventive measures by ICU staff is thus...

Internal Transcribed Spacer

The diversity of the intergenic spacer regions is due in part to variations in the number and type of tRNA sequences found among these spacers. Sequence of ITS region has been used for identification of mycobacterial species, for staphylococcal species (Couto et al., 2001), streptococcal species (Chen et al., 2004), and for rapid identification of medically important yeast (Chen et al., 2001). In staphylococci, there are several copies of the rrn operon. Guirtler and Barrie (1995) characterized the spacer sequences of S. aureus strains, including methicillin-resistant S. aureus (MRSA) isolates, and identified nine rrn operons whose 16S-23S spacer region varied from 303 to 551 bp. Three of these spacers contain the tRNAIle gene and two contain both the tRNAIle and the tRNAAla genes, while the remaining four 16S-23S spacers have no tRNA gene. Forsman et al. (Forsman et al., 1997) sequenced the 16S-23S spacer of five staphylococcal species (S. aureus, S. epidermidis, S. hyicus, S....

Microorganisms and Antibiotic Resistance

Recently, an emergence of infections, mostly skin infection but sporadically severe CAP, caused by so-called community-associated methicillin-resistant S. aureus (CA-MRSA), have been reported from the United States and Europe.64, 65 CA-MRSA are resistant to all p-lactam antibiotics, but are frequently still susceptible to clindamycin, co-trimoxazole, and fluoroquinolones.

Empiric Treatment of Ventilator Associated Pneumonia

Group I patients without risk factors, and less than 5 days' hospitalization. Potential microorganisms are methicillin-sensitive Staphylococcus aureus, anaerobes, Haemophilus influenzae, Streptococcus pneumoniae, and Enterobacteriaceae (Escherichia coli, Klebsiella pneumoniae, Enterobacter spp., Proteus spp., Serratia marcescens). Group II patients with risk factors or more than 5 days' hospitalization. The most likely microorganisms isolated would be those present in group I and resistant organisms such as Pseudomonas aeruginosa, Acinetobacter spp., Citrobacter spp., Stenotrophomonas maltophilia, or methicillin-resistant S. aureus (MRSA).

Empiric Treatment of Group I VAP

The critical factor for changes in the expected flora is prior antimicrobial use (Alvarez-Lerma 1996, Luna et al. 1997, Kollef et al. 1999, Kollef 2000. The patients with the highest risk of developing VAP with endogenic flora are probably those with acute neurologic injuries such as head injury or cardiac arrest. There is a tendency for patients with head injury to be infected colonized by S. aureus. The presence of MRSA needs to be considered in patients with recent hospitalizations or long-term institutionalization (Rello etal. 1992). Mortality from early onset VAP is about 24 . VAP also increases time on mechanical ventilation, ICU and hospital stay, morbidity, and, therefore, associated costs (Heyland et al. 1999).

Empiric Treatment of Group II VAP

Hospital units with a high prevalence of MRSA, especially if a p-lactam has been previously administered, must include a glycopeptide or linezolid in empiric therapy. Recent data show higher survival rates in patients receiving linezolid than in those receiving vancomycin (80 versus 64 ) (Rubinstein etal. 2001, Wunderink et al. 2003b).

Combination versus Monotherapy

Monotherapy should be used when possible, because combination therapy is often expensive and exposes patients to unnecessary antibiotics, thereby increasing the risk of MDR pathogens and adverse outcome. Patients who develop nosocomial pneumonia with no risk factors for drug-resistant organisms are likely to respond to monotherapy. Monotherapy is also the standard when Gram-positive HAP or VAP, including MRSA, is documented.

Multiresistant Infections

Methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant ente-rococci (VRE), Acinetobacter spp, and extended spectrum p-lactamase-producing Enterobacteriaceae (ESBL).10-13 The epidemiology and control of such multire-sistant organisms has been the subject of many previous publications and is not within the scope of this review. Suffice to say, they continue to plague many ICUs causing major problems.

Molecular Epidemiology

Molecular techniques dedicated to bacterial detection and identification have been recently reviewed (Nolte et al., 2003 Diekema et al., 2004). In the case of MRSA, the mecA gene encoding for the low-affinity penicillin-binding protein PBP2' is the genetic basis of methicillin resistance in MRSA isolates. This gene, originating from a mobile genetic element designated SCCmec staphylococcal cassette chromosome mec (Katayama et al., 2003) , flanked by terminal inverted and direct repeats (Ito et al., 2001), is invariably inserted into the orfX gene of S. aureus chromosome (Fig. 24.1). This element contains two site-specific cassette chromosome recombinases, ccrA and ccrB, responsible for the precise excision and integration of SCCmec within the bacterial chromosome (Katayama et al., 2003). To date, five differently organized SCCmec elements have been characterized (Ito et al., 2003). Three types of SCCmec elements are typically found in HA-MRSA strains (i) type I, a 34-kb element that...

Simultaneous Measurement of Microbes and Toxins

Novel methods for simultaneously measuring the levels of specific microbes and their products in complex specimens are also possible. As an example, a cytomet-ric bacteria and protein assay (CBPA) was developed (Bolton et al., 2002). For the sandwich flow cytometric immunoassay component of the CBPA, antibodies were generated against Staphylococcus aureus enterotoxin B (SEB) and ricin. The antibodies were used to prepare two distinct sets of single-color fluorescent capture beads and PE-conjugated DAb. Purified preparations of SEB and Ricin communis agglutinin II served as calibrators. In this case, the identification of bacteria used the capability of the flow cytometer to detect bacteria directly by light scatter or dye-mediated nucleic acid fluorescence. The specific identification was achieved with fluorochrome-labeled species-specific antibodies. The use of membrane permeable and impermeable nucleic acid dyes allowed for the discrimination of live and dead cells. For the...

Empiric Treatment Choices for Multiresistant Organisms

For understandable reasons there are few randomized clinical studies. Recent comparative studies of linezolid versus van-comycin or teicoplanin in VAP and skin and soft tissue infections (SSTI)59, 60 show superiority of linezolid in MRSA infections on subanalysis but no studies MRSA c MRSA, methicillin-resistant Staphylococcus aureus VRE, vancomycin-resistant Enterococcus spp. GISA VRSA, glycopeptide intermediate Staphylococcus aureus vancomycin-resistant Staphylococcus aureus ESBL, extended-spectrum p-lactamase producer. d Keep trough at 20 mg liter. e If bacteremic, delay rifampicin for 2 days. f To prevent selection of resistance to linezolid. g Depends on local susceptibilities. h Not E. faecalis. have compared linezolid against a glycopeptide in combination with another agent. Such combination therapy is now commonplace with the realization that the glycopeptides, while long thought to be the last option for MRSA, are only slowly bactericidal,...

Technology Comparison

Discrimination to the subspecies or strain level is essential to a clinical strain-typing system because many organisms, such as methicillin-resistant Staphylo-coccus aureus (MRSA), are extremely heterogeneous. Although some typing systems may be valid for more diverse organisms, many fail to discriminate at the strain level for these clinically important organisms. For example, ribotyping often has difficulty distinguishing among different subtypes (Kostman et al., 1995 Lobato et al., 1998), and 16S rRNA sequencing often shows low levels of subspecies and strain discrimination (Sander et al., 1998 Barney et al., 2001 Callon et al., 2004). Additionally, plasmid typing and MLEE provide only an estimate of genetic relatedness (Mayer, 1988 Seifert et al., 1994a, 1994b Trindade et al., 2003). The DiversiLab System provides genus-specific kits that have been developed for a high level of strain discrimination. However, universal kits, such as the DiversiLab Gram-negative kit, can be used...

Infections Caused by Community Acquired Organisms Colonization Recurrence or Reinfection

There has been awareness of community-acquired pathogens, but that phenomenon is now being more carefully studied as it appears that the level of community acquisition is somewhat organism dependent. The prevalence of community-acquired MRSA has increased, as confirmed by the use of microbial strain typing (Herold et al., 1998 Fey et al., 2003), and the increase of community-acquired infections makes the determination of HAI increasingly difficult. In order to understand the transmission and source of MRSA outbreaks, strain typing must be used to compare community-acquired and nosocomial pathogens at the genomic level The etiology of infectious diseases includes the potential infection not only from community sources but also from colonization of patients or health care workers. Because MRSA can colonize healthy individuals, screening of employee strains may indicate routes of transmission. One study using PFGE found that of seven staff members, three carried the same strain as found...

Surveillance for Potential Infections

Although the debate continues over what may be the most cost-efficient and necessary approach for prospective monitoring of health care-associated infections, it is clear that surveillance is the first step to understanding and management (Peterson and Brossette, 2002). One way the microbiology laboratory can aid in surveillance is by screening patient admission isolates. MRSA colonization of nares, either present at admission to the hospital or acquired during hospitalization, increases the risk of MRSA infection. Identifying MRSA colonization at admission could target a high-risk population that may benefit from interventions to decrease the risk for subsequent MRSA infection (Davis et al., 2004). However, there remains some controversy on how to best apply the results to infection-control practices. Surveillance cultures and genotyping of MRSA and Methicillin-Resistant Staphylococcus aureus (MSSA) isolates demonstrated the absence of cross-transmission among patients in the medical...

Infection Control Measures

Colonized and infected patients represent the main reservoir of MRSA in hospitals. Healthcare workers may carry MRSA, although most often transiently. More importantly, healthcare workers may transmit the bacterium from one patient to the other on their contaminated hands or clothes. Transmission also occurs through contamination of the environment or the equipment. Infection control measures are therefore pivotal in preventing hospital transmission of MRSA. This implies a strict application of standard precautions, especially hand hygiene. Additional measures are recommended in MRSA-positive patients and typically include contact precautions with or without isolation in individual rooms, disinfection of the environment, and decolonization protocols. These protocols have not been standardized. They most often include topical disinfection and intranasal mupirocin, and sometimes systemic antibiotics. Although the impact from the individual components of these preventive measures has not...

Policies for Appropriate Use of Antibiotics

The appropriate use of antibiotics is of interest for the prevention of MRSA infections not only for perioperative antibiotic prophylaxis but also because antibiotic consumption in general is a major contributor to emerging bacterial resistance. Several studies indeed suggest that antibiotic consumption is a risk factor for colonization or infection by MRSA at the level of the individual patient, as well as a determinant of the epidemiology of MRSA at the collective level. Receipt of antibiotics within the previous months predisposes the individual patient to infection with or carriage of MRSA (Hidron et al. 2005). This finding has been repeatedly reported with fluoroquinolones (Crowcroft etal. 1999, Dziekan et al. 2000, Graffunder and Venezia 2002, Harbarth et al. 2000). Weber et al. specifically designed a case-case-control study to determine whether exposure to fluoroquinolones was a risk factor for the subsequent isolation of MRSA or MSSA (Weber et al. 2003). Both levofloxacin and...

Culture Confirmation and Tissue Pathogen Detection by Direct In Situ Hybridization

Though in situ hybridization (ISH) is typically performed in histology rather than clinical microbiology laboratories, it can provide extremely useful information to clinical microbiologists. Several pathogen targets have been used for direct hybridization to nucleic acid probes in situ. Bacterial targets include Helicobacter pylori (Makristathis et al., 2004), and Legionella spp. (Hayden et al., 2001b). Yeast forms of the dimorphic fungi (Hayden et al., 2001a), and molds such as Aspergillus spp., Fusarium spp., and Pseudoallesheria spp. (Hayden et al., 2002, 2003) have also proven to be useful as ISH targets. Typically, in situ hybridization is chosen when it is useful for the pathogen to be identified in association with intact cells or tissue, but branched DNA probes have been used to identify the presence of human papilloma virus (HPV) and the gene expression signal from HPV mRNA (Kenny et al., 2002). As a method for culture confirmation, PNA FISH (peptide nucleic acid fluorescent...

Overnight Biochemical Tests

The overnight biochemical tests are a group of tests that require inoculating one or more culture media containing specific substrates and chemical indicators that detect pH change or specific microbial by-product. Similar to rapid tests, the choice of overnight tests is based on Gram-stain morphology and the results of preliminary testing with rapid enzyme tests. These tests are also inexpensive and easy to perform and may be used in three different ways. They may be used to obtain important initial information with respect to the identity of an unknown organism, such as the MILS test, which is used to screen for the presence of enteric pathogens. They may be used to verify the results of a preliminary positive negative test or they may be used to assess an indeterminate finding. For example, Taxo P is an overnight test that will demonstrate if an isolate with an equivocal bile solubility result is S. pneumoniae. Similarly, a tube coagulase test will substantiate if a suspicious...

Peptide Nucleic Acid Probe

PNA FISH probes have been developed and evaluated for S. aureus, C. albicans, E. faecalis, E. coli, coagulase-negative staphylococci, C. dubliniensis, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Among these probes, currently the S. aureus PNA FISH, C. albicans PNA FISH, and E. faecalis PNA FISH are FDA approved for in vitro diagnosis and are available from AdvanDx, (Woburn MA, USA). The PNA FISH procedures have been extensively evaluated for rapid diagnosis of positive blood cultures for S. aureus (Chapin and Musgnug, 2003 Oliveira et al., 2002, 2003), E. coli, and C. albicans (Oliveira et al., 2001, Rigby et al., 2002) with high sensitivity and specificity. A recent multicenter evaluation (Wilson et al., 2005) of the C. albicans PNA FISH assay (AdvanDx) demonstrated that this method is an accurate means of differentiating C. albicans from non-C. albicans species present in blood culture bottles. The overall sensitivity, specificity, positive predictive value, and negative...

Molecular Detection of Drug Resistance

Perhaps the most well-documented applied use of markers for bacteria are those of oxacillin-resistant Staphylococcus aureus (ORSA, formerly MRSA) and vancomycin-resistant enterococcus (VRE). The mecA gene mediates oxacillin resistance in most ORSA, and the vanA and vanB genes primarily mediate acquired vancomycin resistance in VRE. Commercially available tests for ORSA include latex agglutination tests for PBP2a (the product of mecA), cycle probe technology, and PCR for the detection of mecA in S. aureus. PCR has been used to detect and track both ORSA and VRE (Clark et al.,1993 Gordts et al. 1995 Aarestrup et al., 1996 Satake et al., 1997 Hussain et al., 2000 Padiglione et al., 2000 Grisold et al., 2002 Jonas et al., 2002 Louie et al., 2002 Maes et al., 2002 Francois

Source Tracking of Pathogens in Outbreak and Clonal Spread

Methicillin-resistant Staphylococcus aureus is currently the most common antibiotic-resistant pathogen reported associated with HAI in the United States (CDC, 2004). Even in previously unaffected countries, MRSA has become a common problem (Faria et al., 2005). Strain typing of MRSA is important for performing outbreak investigations of nosocomial infections. Tracking the strains of MRSA in a facility over time has previously demonstrated a shift in the type of organism most commonly seen (Perez-Roth et al., 2004). Strain typing can also reveal the spread of a clone not only through a hospital but to a different facility. For example, strains in Hong Kong were linked to clones with United Kingdom and Brazilian lineages (Ip et al., 2003). The resistance profiles of MRSA clones can vary widely strain typing provides a method of distinguishing these clones (Coombs et al., 2004). MRSA is a clonal organism that is difficult to strain type with many common genotypic techniques. PFGE is...

Disk Diffusion Testing

The diameters of growth inhibition zone should be measured from the edge of the ring with no bacteria growth. Discrete colonies within a clear inhibition zone are the results of either heterogeneous resistance among the bacteria population or contaminated culture. The heterogeneous resistance has been observed in staphy-lococci tested with oxacillin (Brown, 2001) and vancomycin (Liu and Chambers, 2003 Rybak et al., 2005), enterococci with vancomycin, and Enterobacter spp. with penicillins and cephalosporins (Hsieh, 2000). When such organism-drug combinations are tested, any amount of colony growth in the inhibition zone is an indication of resistance. Swarming Proteus spp. sometimes produce a thin film of swarming growth inside the inhibition zone. The margin around the heavy growth should be used for measuring the diameters of zones of inhibition. For bacterio-static agents, the zone diameters of 80 growth inhibition are measured. The disk diffusion test is easy to perform. It allows...

Signal Mediated Amplification of RNA Technology

Levi et al. evaluated the SMART assay (CytAMP assay kit, Cytocell Ltd., Adderbury, Oxford, UK) for the rapid detection of methicillin (oxacillin)-resistant Staphylococcus aureus (MRSA) (Levi et al., 2003). Two sets of probes were designed against the coa (coagulase) and mecA (methicillin resistance) genes, respectively, hence, simultaneous identification of S. aureus and methicillin (oxacillin) resistance is possible. The detection limit of the assay was 2 x 105 and 106 CFU assay for mecA and coa, respectively. When tested with S. aureus isolates, the assay detected 113 MRSA among 396 S. aureus with 100 sensitivity and specificity, compared with a mecA-femB PCR assay. When 100 enrichment broths containing sets of screening swabs from individual patients were tested, the presence of MRSA was detected in 19, 24, and 31 enrichment broths by SMART assay, conventional culture, and mecA-femB PCR, respectively. Six enrichment broths were found negative by SMART assay but positive by both PCR...

Molecular Differential Diagnostic System for Health Care Associated Infections

Staphylococcus aureus Staphylococcus aureus (MRSA) common in HAI. In addition to detecting common HAI pathogens, the MDD system for HAI I also detects two targets related to drug resistance the mecA gene and Class I integron. The mecA gene is specific for methicillin-resistant Staphylococcus aureus (MRSA). The Class I integron is commonly seen in Gramnegative bacteria that have resistance to multiple antibiotics.

Sequence Based Bacterial Genome Typing

Spa Typing of Staphylococcus aureus Many techniques are available to differentiate S. aureus, and specifically MRSA, isolates. Conventionally, isolates were distinguished by phenotypic methods, including antibiotic susceptibility testing and bacteriophage typing. Both methods have limitations, as genetically unrelated isolates commonly have the same antibiogram, and many S. aureus isolates are nontypeable by phage typing. With the advancement of molecular biology, strain typing focused on DNA-based methods restriction endonuclease patterns of chromosomal or plasmid DNA, Southern blot hybridization using gene-specific probes, ribotyping, polymerase chain reaction (PCR)-based approaches, and pulsed-field gel electrophoresis (PFGE). These methods require subjective interpretation and comparison of patterns and fingerprint images. Nucleotide sequence analysis is an objective genotyping method sequencing data can be easily stored and analyzed in a relational database. Recent advances in...

Infection Control Practices

Health care workers hands may not be the only source of transmission. The contaminated clothing of health care workers may also contribute to transmission of organisms. One study showed that 37 of health care worker's gowns were contaminated with VRE after care of a colonized patient. Another study has shown that 40 of the time, health care workers' gowns were contaminated with MRSA or VRE after caring for colonized patients and that gowns prevented clothing contamination. 'White coats' become contaminated with VRE or MRSA after examining a patient and the organisms may be transferred to the health care workers' hands 27 of the time after touching the coat 11 . In some health care settings, long-sleeved clothing has been banned for infection control purposes. Decontamination of patients' skin and the environment also can be important infection-control measures. VRE can be transferred from contaminated sites in the environment or on patients' intact skin to clean sites via health care...

Aspects of Virulence Toxin Production

S. aureus produces many toxins, one of which, the staphylococcal a-toxin, is a major virulence determinant encoded by the hla gene (Bhakdi and Tranum-Jensen 1991). It has been shown that growing S. aureus in the presence of the p-lactam antibiotic, nafcillin, induces a-toxin expression and increases the lethal activity of broth filtrates in rats (Kernodle et al. 1995). These findings led to the speculation that p-lactam therapy might enhance the virulence of some S. aureus strains, in turn worsening the symptoms of serious staphylococcal infection. Therefore, the effects of other antibiotics have been tested by measuring the induction of hla expression after exposure to different strains of S. aureus (Ohlsen et al. 1998). There was a strong induction of hla expression by subinhibitory concentrations of several p-lactam antibiotics, including some cephalosporins and imipenem. Fluoroquinolones slightly stimulated expression, glycopeptide antibiotics had no effect, and erythromycin and...

Relationship Between Past and Future Pandemics

The introduction of protein-conjugate vaccine for Haemophilus influenzae B in the 1990s led to important reductions in this invasive disease 94 . During that same decade, the prevalence of antimicrobial-resistant S. pneumoniae in the United States increased dramatically 95 . This increase reversed following the introduction of pneumococcal conjugate vaccine into the routine infant immunization schedule. Whether this trend will continue or reverse yet again remains to be seen 96 . Perhaps the most novel aspect of a pandemic now or in the future will be the role of community-associated MRSA. As mentioned previously, the increase in prevalence of methicillin resistance among S. aureus isolates has become an important concern among clinicians, both because of the rate of increase in prevalence and because of the dramatic clinical presentations 36-38, 42, 54, 73 .

Prevention and Control of Multiresistant Infections

This variance is not surprising as the non-European Mediterranean countries are, to a varying extent, also still developing their socioeconomic, educational, and healthcare infrastructures to reach levels comparable to those of their Western counterparts. In developing countries, substantial deficiencies in healthcare quality and delivery are often due to insufficient budgets, low salaries for health personnel, and diversion of resources to areas of higher priority or to produce more tangible investments (Meers 1998). Nevertheless, it would be difficult to explain the lack of IC initiatives based solely on these premises, as even in the more affluent European countries bordering the northern Mediterranean shores, implementation of IC programs has also been shown to be less than comprehensive. Moro and colleagues (2003) also showed that just 1.6 of surveyed Italian hospitals had a policy for the control of MRSA infections. Inadequate resources and lack of trained personnel were cited...

The Role of the Microbiology Laboratory

The greatest challenge for the microbiology laboratory in the treatment of infection on the ICU is to make results available on a time scale that can influence treatment and there is reasonable hope that molecular tests will facilitate this. For bacterial infections, however, the only widely available molecular test, commonly relevant to the ICU, is PCR for the mecA gene of MRSA.44 No molecular test is generally available for rapid diagnosis of invasive fungal infection, and while PCR for viral infections is making great inroads, it is outside the scope of this review. It is common now to screen all admissions to the ICU for MRSA. Isolation precautions can then be taken to prevent spread and early decolonization of MRSA-positive patients attempted.50 Early assessment of MRSA carriage status can also inform empiric therapy should it be necessary.

Molecular Differential Diagnostic System for Gram Positive Cocci in Clusters

Rapid identification of methicillin-resistant Staphylococcus aureus (MRSA) is critical for the effective treatment of patients and to control the spread of the pathogen (Farr et al., 2001). An ideal MDD test should be able to distinguish coagulase-positive Staphylococcus (Staphylococcus aureus) from coagulase-negative Staphylococcus (CoNS) methicillin-sensitive Staphylococcus aureus (MSSA) from MRSA and hospital-acquired MRSA (HA-MRSA) from community-acquired MRSA (CA-MRSA). An added benefit would be if such a test could identify some of the most common drug-resistance genes in the same assay. for the simultaneous detection of Staphylococcus aureus and coagulase-negative Staphylococci in positive blood cultures. Louie et al. (2002) reported the development of a multiplex PCR assay that identifies three genes (nuc, mecA, and bacterial 16S rRNA genes) for the differentiation of MSSA and MRSA. Samples were collected from blood culture bottles, and PCR products were analyzed using gel...

Conclusion and Recommendation

HA-MRSA is a major nosocomial pathogen with major impact on the healthcare systems of almost every country in the world. In countries with high rates of HA-MRSA, mortality and morbidity attributed to infections caused by this organism is high, as is the financial burden of therapy and prolonged hospitalization. In countries with low rates, the prevention of MRSA from becoming endemic is responsible for a lower, but still significant financial outlay. However, prevention is less expensive than therapy of MRSA infections, and intensive infection control aimed at reducing MRSA rates is strongly recommended in low-prevalence settings. Unfortunately, in most countries MRSA has become endemic. It is not clear how to reduce MRSA rates most effectively in these settings. Screening for asymptomatic carriage, screening of HCWs, and reliable laboratory methods are crucial for success. Infection control programs that do not take into account the role of asymptomatic carriers (both patients and...

Isbn 9783805593236

1 Community-Associated Methicillin Resistant Staphylococcus aureus Since antimicrobial drugs were first discovered and used during the Second World War, they have saved countless lives and eased the suffering of millions of people. Unfortunately, in recent years we have seen the emergence and spread of microbes that have acquired resistance to many of the antibiotics in widespread use. Some of the most important of these are penicillin-resistant Streptococcus pneumoniae, van-comycin-resistant enterococci, multidrug-resistant salmonellae and Mycobacterium tuberculosis, and methicillin-resistant Staphylococcus aureus (commonly known as MRSA). community-acquired infections and Enterococcus spp. that cause bloodstream infections in hospitalized patients), carbapenems (resistance in Klebsiella pneumoniae that causes healthcare-associated infections), quinolones (resistance in various Gram-negative and Gram-positive bacteria such as Escherichia coli causing urinary tract infections and...

Conclusion

It is not impossible that in the future we might experience a global pandemic of some multiply resistant pathogen that seeks to rival the postulated impact of avian influenza. Indeed the impact of any strain of pandemic influenza would be significantly accentuated by MRSA. Events such as this would put antimicrobial resistance firmly on the political agenda and help prioritize the research required for finding another way of treating infection.

Agar Dilution

Agar dilution is one of the standardized antimicrobial testing methods. Mueller-Hinton agar (MHA) is used for testing nonfastidious aerobic and facultatively anaerobic bacteria that require no special supplement for growth. To prevent the interference to drug activity, any calcium and magnesium containing supplement should not be added (NCCLS, 1996). Culture medium mentioned above in dehydrated form is commercially available. Preparation of the agar plates should follow the manufacturer's recommendations. Drugs are tested at serials of twofold dilutions with each plate containing one concentration. The range of concentration tested for each drug should cover the CLSI break points and the expected MICs for quality control reference strains. Studies show that the oxacillin MIC for Staphylococcus spp. carrying the mecA gene are detected with increased sensitivity by the agar containing NaCl (Huang et al., 1993). Therefore, MHA with 2 NaCl is recommended for the testing of staphylococci...

Broth Dilution

Similar to agar dilution method, broth dilution methods test the organisms in medium containing antimicrobial agents in serials of twofold dilutions. Instead of growing bacteria on solidified medium, bacteria are grown in liquid medium during susceptibility test process, and at the end of the test, bacterial growth is evaluated by the turbidity of broth. Macrodilution testing is performed in serials of 13 x 100 mm tubes with each one containing 2 mL of broth. Microdilution testing uses multiwell microdilution trays with each well containing 0.1 mL of broth. Because the microdilution trays with prepared panels of antimicrobial dilutions either frozen or freeze-dried are commercially available, allowing testing of multiple organisms simultaneously, the method has replaced macrodilution and has been widely used in clinical microbiology laboratories. Cation-adjusted Mueller-Hinton broth (CAMHB) is recommended for standardized broth dilution methods (NCCLS, 2003). The cations Ca2+(20 to 25...

Genomics

The sequence of one isolate is not necessarily representative of the species, so there is now a trend toward comparative genomics whereby several isolates of one species are sequenced and compared with each other. For example, seven sequences of Staphylococcus aureus are publicly available, including hospital- and community-acquired MRSA (Diep et al. 2006) and a vancomycin intermediate-level resistant MRSA isolate from Japan (Kuroda etal. 2001). This approach enables comparison between sequence and phenotypic characteristics, particularly for virulence traits and antibiotic resistance, and may ultimately help discover ways to prevent new resistance arising and to find susceptibility in already resistant pathogens.

Overview

Antimicrobial resistance in health care facilities is a global public health concern. Over 70 of bacterial pathogens found in US hospitals are resistant to at least 1 antibiotic, and more than 14,000 patients die annually from resistant nosocomial infections. Antimicrobial-resistant microorganisms can be associated with increased mortality and morbidity, prolonged hospital stay and higher costs. For example, patients with bacteremia caused by methicillin-resistant Staphylococcus aureus (MRSA) have longer hospitalizations and higher hospital costs and mortality than do patients with bacteremia caused by methicillin-susceptible S. aureus. Fear of resistance leads physicians to prescribe newer, more expensive antibiotics, costing at least USD 4-5 billion in 1998 in the United States. The combination of highly susceptible patients, prolonged and complex antibiotic use, cross infection due to poor infection control practices (especially lapses in hand hygiene), and shuttling of patients...

Literature Review

Methicillin-Resistant Staphylococcus aureus In terms of cost, MRSA is by far the most studied antibiotic-resistant organism (table 1). Reported costs vary widely between studies due to differences in study populations, Table 1. The economic cost associated with methicillin-resistant Staphylococcus aureus Table 1. The economic cost associated with methicillin-resistant Staphylococcus aureus

Cost of Prevention

The study by Chaix et al. 19 examined the cost of MRSA screening cultures and contact isolation practices in a medical ICU. Costs of the infection-control program, which included screening at-risk patients at admission, weekly surveillance cultures, contact precaution, and hand washing, were computed by summing the cost of supplies, labor, and other operating costs. The total cost of infection-control measures per patient ranged from USD 340 to USD 1,480. Based on the current MRSA prevalence in the ICU (4 ) and an estimate of the effectiveness of contact precautions (reduced MRSA transmission and infection by 15-fold), the authors concluded the MRSA screening cultures and isolation practices were cost effective. In sensitivity analyses, to remain cost effective, a higher MRSA prevalence on admission would be needed (up to 14 ) if the effectiveness of contact precautions were reduced and if fewer infections occurred as a result of MRSA exposure. Perhaps one of the most strict...

Etiology

Worldwide, Streptococcus pneumoniae is by far the most important pathogen for CAP. Other frequently isolated bacteria are Haemophilus influenzae and Staphylococcus aureus.11--3 Incidences of atypical pathogens, such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila, are generally lower than those of the afore-mentioned bacteria, although variations may be large.17, 18, 20, 23 Pseudomonas aeruginosa can be relevant in patients with structural lung damage, such as those with bronchiectasis or COPD.24 Most frequent viral causes of CAP include influenza virus and parainfluenza virus.23, 25 Viral pneumonias due to infection with influenza, respiratory syncytial virus, coronaviruses, parainfluenza virus, and even rhinoviruses can be life threatening in elderly and immunocompromised patients. Influenza pneumonia may be complicated by secondary bacterial infections caused by S. aureus, S. pneumoniae, H. influenzae, or other Gram- negative pathogens.21, 26

Clinical Relevance

Staphylococcus aureus is a major pathogen responsible for both nosocomial and community-acquired infections. Although the first S. aureus isolates displaying resistance to methicillin (MRSA) were reported in the early 1960s (Barber, 1961), endemic strains of MRSA carrying multiple resistance determinants did not become a worldwide nosocomial problem until the early 1980s (Hryniewicz, 1999). The presence of MRSA in an institution is paralleled by an increased rate of bacteremia or other severe MRSA infections (Harbarth et al., 2000). MRSA-related bacteremia carries a threefold attributable cost and a threefold excess length of hospital stay when compared with methicillin-susceptible S. aureus (MSSA) bac-teremia (Abramson and Sexton, 1999). Recently, the apparition of endemic community-acquired MRSA (CA-MRSA) has been reported (Naimi et al., 2003 Saiman et al., 2003). In contrast to hospital-acquired MRSA (HA-MRSA), CA-MRSA are frequently isolated from healthy people and strains are...

Download Instructions for Staph Infection Secrets By Dr. Walinski

The best part is you do not have to wait for Staph Infection Secrets By Dr. Walinski to come in the mail, or drive to a store to get it. You can download it to your computer right now for only $29.95.

Download Now