Microbial factors leading to recurrent upper respiratory tract infections.

The treatment or prophylaxis of upper respiratory tract infections such as otitis media, sinusitis and tonsillitis with penicillins can generate bacterial resistance caused by production of beta-lactamase or changes in the penicillin-binding proteins. This resistance can spread in the community even to untreated individuals. The prevalence of resistant organisms tends to increase in the winter months. Beta-lactamase-producing bacteria may interfere with the eradication of penicillin-susceptible organisms and may account for substantial numbers of therapeutic failures among cases of otitis media, sinusitis and tonsillitis. The presence of normal flora that possess interfering capabilities against potential pathogens is beneficial to the host. Such flora may enhance recovery and prevent infections of the tonsils by group A beta-hemolytic streptococci. Therapeutic use of antimicrobial agents that preserve the normal flora but overcome penicillin-susceptible or -resistant pathogens may enhance recovery from upper respiratory tract infections.