The role of anaerobic bacteria in sinusitis.

The normal oropharyngeal flora contained aerobic and anaerobic bacteria that can cause respiratory infections including sinusitis. Some of these bacteria can interfere with the growth of potential pathogens and may play a role in preventing infections. Anaerobic bacteria emerge as pathogens as the infection becomes chronic. This may be the result of the selective pressure of antimicrobial agents that enable resistant anaerobic organisms to survive, and from the development over time of conditions appropriate for anaerobic growth, which include the reduction in oxygen tension and an increase in acidity within the sinus cavity. Anaerobes were isolated in acute maxillary sinusitis of odontogenic origin and in over half of the patients with chronic sinusitis whenever proper techniques for their cultivation were employed. These organisms were also recovered in acute sinusitis that was associated with dental infections. The predominant isolates were pigmented Prevotella and Porphyromonas, Fusobacterium and Peptostreptococcus spp.