Infections of the upper respiratory tract, head, and neck. The role of anaerobic bacteria.

Anaerobic bacteria predominate in the normal flora of the human oropharynx and therefore are a common cause of endogenous bacterial infections of the upper respiratory tract. They are found in chronic otitis media and sinusitis, play a pathogenic role in tonsillitis, and are important contributors to complications of these infections. Anaerobes also predominate in deep oral and neck infections and abscesses. Their direct pathogenicity in these infections is compounded by their ability to produce beta-lactamase, which allows anaerobes to "shield" non-beta-lactamase-producing bacteria from penicillin activity. Their slow growth, polymicrobial nature, and growing resistance to antimicrobial agents complicate treatment. Usually, antimicrobial therapy is all that is needed, but in some cases, it serves as an important adjunct to surgical intervention. Adequate antimicrobial coverage of both anaerobic and aerobic bacteria is essential because culture usually reveals a mixed infection. Failure to select the appropriate antibiotics may lead to clinical failure.