Microbiology

Acute Sinusitis

The most commonly identified organisms in children with acute sinusitis are Streptococcus pneumoniae in 30-40%, Haemophilus influenzae in 20-25%, and Moraxella catarrhalis in 20%. In adults, S.pneumoniae and H. influenzae are the two leading causes of sinusitis, whereas Moraxella is unusual. Anaerobic organisms are primarily identified in cases of acute sinusitis originating from dental root infections, but are otherwise uncommon. Hospital-acquired sinusitis is most often seen as a complication of nastogastric tube placement and is typically caused by Gram-negative enteric organisms such as Pseudomonas and Klebsiella.

Chronic Sinusitis

Bacterial isolates in children with chronic sinusitis are usually the same as those seen in acute disease. in children with more severe and protracted symptoms, anaerobic species (such as Bacteroides) and staphylococci are cultured more frequently.

Anaerobic organisms and increasingly Staphylococcus epidermidis predominate in adults with chronic sinusitis. Among the anaerobes, species of Bacteroides and anaerobic cocci account for most of the isolates. However, the role played by these organisms in adults with chronic sinusitis is not entirely clear. Some investigators have suggested that coagulase-negative staphylococcal species may act as antigens that elicit a chronic inflammatory response in the mucosa.

Fungi may cause invasive infection in immunocompromised hosts, including diabetics and patients with defective cell-mediated immunity. These infections may progress rapidly and eventuate in severe complications are even death. Rarely, Aspergillus, Nocardia, and Bipolaris species have also been identified as causes of chronic, indolent, yet invasive sinusitis in patients who are otherwise healthy. Allergic fungal sinusitis is a syndrome that has been attributed to Aspergillus, Bipolaris, and Curvularia species.

Table 4

Antibiotic Treatment of Acute Sinusitis

• Mild symptoms

Amoxicillin 45 mg/kg given in two doses For non-type-1 hypersensitivity reactions: Cefdinir 14 mg/kg/d in one or two doses Cefuroxime 30 mg/kg/d in two doses Cefpodoxime 10 mg/kg/d in one dose For type 1 hypersensitivity reactions: Clarithromycin 15 mg/kg/d in two doses

Azithromycin 10 mg/kg/d on day 1, with 5 mg/kg/d4 d in one dose Clindamycin 30-40 mg/kg/d in three doses

• Moderate-severe symptoms" (or failure to respond to amoxicillin or recent use of antibiotics or attendance at day care) Amoxicillin-clavulanate 80-90 mg/kg/d of amoxicillin component, with 6.4 mg/kg/d of clavulanate in two doses Cefdinir, per above Cefuroxime, per above Cefpodoxime, per above

"Moderate-severe symptoms defined as a temperature of >102°F (39°C) and purulent nasal discharge present for at least 3 consecutive days in a patient who seems ill.

It is characterized by severe, hyperplastic sinusitis and nasal polyposis and is associated with an elevation of specific immunoglobulin (Ig)E to the fungus in question, total IgE, and eosinophilia of sinus tissue and blood. Although some investigators have suggested that fungi may cause chronic sinusitis via a noninfectious, non-IgE-mediated mechanism, there is at present insufficient evidence to support this theory.

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