Sinusitis generally develops as a complication of viral or allergic
inflammation of the upper respiratory tract. The bacterial pathogens in acute
sinusitis are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, while anaerobic bacteria and Staphylococcus aureus are predominant in chronic
sinusitis. Pseudomonas aeruginosa has emerged as a potential pathogen in immunocompromised patients and in those who have nasal tubes or
catheters, or are intubated. Many of these organisms recovered from
sinusitis became resistant to
penicillins either through the production of
beta-lactamase (H. influenzae, M. catarrhalis, S. aureus, Fusobacterium spp., and Prevotella spp) or through changes in the
penicillin-binding protein (S. pneumoniae). The pathogenicity of
beta-lactamase-producing bacteria is expressed directly through their ability to cause
infections, and indirectly through the production of betalactamase. The indirect pathogenicity is conveyed not only by surviving
penicillin therapy, but also by 'shielding'
penicillin-susceptible pathogens from the
drug. The direct and indirect virulent characteristics of these bacteria require the administration of appropriate antimicrobial
therapy directed against all pathogens in
mixed infections. The antimicrobials that are the most effective in management of acute
sinusitis are
amoxycillin-
clavulanate (given in a high dose), the newer
quinolones (
gatifloxacin,
moxifloxacin) and the
second generation cephalosporins (
cefuroxime,
cefpodoxime,
cefprozil or
cefdinir). The antimicrobials that are the most effective in management of chronic
sinusitis are amoxycillinclavulanate,
clindamycin and the combination of
metronidazole and a
penicillin.