Antibiotic Resistance Occurs with Avian Flu H5N1

Strategic use of antiviral agents requires that a pandemic virus be susceptible to existing antiviral drugs. Susceptibility may be true at the beginning of an outbreak, but it cannot be known in advance because the pandemic virus is unknown. The government plan also assumes that the virus will remain susceptible to the drugs during widespread use. Given what we know about influenza viruses, this is problematic. Adamantane resistance has been developing for several years (see Box 11-2), as these...

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...

Most Antifungal Agents Attack Membranes and Cell Walls

All cells are surrounded by a semi-permeable membrane that contains a variety of proteins, lipids (fats), and sterols. Cholesterol is one of the sterol components of mammalian cell membranes. Fungal cells are biochemically similar to human cells, but their membranes contain ergosterol rather than cholesterol. The enzymes responsible for making ergosterol differ from those involved in making cholesterol consequently, drugs that interfere with ergosterol formation are specific to fungal cells....

Box 14 Vaccine Resistant Pathogens

Vaccines typically instruct the human immune system to recognize a pathogen and destroy it. In some circumstances, the pathogen can alter its surface properties to make it less responsive to the immune system. For example, the malaria parasite frequently changes its surface consequently, the human immune system is always a step behind the parasite. In other cases, the pathogen species exists in many varieties. Shortly after the U.S. anthrax scare of 2001, considerable concern arose because the...

Herpes Virus

Herpes viruses are large DNA viruses (see Figure 3-4) categorized into eight distinct types that replicate in skin cells where the virus causes lesions. In the case of herpes simplex, the lesions are often called cold sores or fever blisters. These sores heal within a couple of weeks, but they recur, often when a person is under stress. A variety of stressors, such as sunlight, activate the virus. The source of recurring outbreaks appears to be infected nerve cells that harbor the virus in a...

Box 81 Surveillance Networks for Antibiotic Resistance

Many of the major surveillance networks were established in the late 1990s,182 a time when resistance became recognized as a widespread problem. However, nosocomial infections had been recognized for decades, as evidenced by establishment of the National Healthcare Safety Network (NHSN) in 1970 for U.S. hospitals.182 By the end of the 1990s, several networks were in place for European hospitals (HELICS, 1994 EARSS, 1998) and U.S. intensive care facilities ((ICARW, 1995). Respiratory infections...

Antiviral Resistance Has Emerged Among Seasonal Influenza Virus

Flu vaccines are only 70-90 effective.229 Consequently, antiviral drugs have been developed for persons unable to develop a good immune response to the vaccine. Influenza viruses fall largely into two general types called A and B. (In the 2008-09 season, 77 were type A, 23 were type B.230) Two antibiotic classes have been used for influenza A. The adamantanes (amantadine, rimantadine) inhibit influenza virus membrane protein-2 (M2). This protein is part of a channel required for passage of...

Avian Flu H5N1 Is a Candidate for Deadly Pandemic

Since 2003, avian flu has received considerable attention as a potential pandemic virus. This version of influenza A, caused by subtype H5N1, is endemic to Southeast Asia. In the late 1990s, it began its worldwide spread via birds, and between 2003 and September 2008 it caused 387 documented human deaths.232 The human death toll was small, largely because transmission of virus occurred from bird to human rather than from human to human. The unsettling number was the crude mortality rate a...

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...

Fungi Are Eukaryotes Having Cell Walls But Not Chloropasts

Yeasts, molds, and mushrooms are fungi. Unlike bacteria, fungal cells store their DNA in true nuclei. Such subcellular structures, called organelles, localize particular cellular functions. For example, mitochondria are power plants that convert chemical energy from sugars into molecules such as ATP. Lysosomes are the cellular equivalent of garbage disposal units. They are filled with enzymes that destroy other macromolecules. Bacterial cells lack such localization of cellular activity. In...

Box 103 Vaginal Yeast Infections

The female genitourinary tract is colonized with yeasts, in particular Candida albicans. These fungi are normally balanced by bacterial flora. The use of antibiotics or changes in the local environment due to hormones or other physiological conditions can result in proliferation of yeasts. As a society, we encourage individuals to self-diagnose and self-treat by making available over-the-counter antifungal agents that are applied topically to the surface of mucosal membranes. Although...