Penicillin failure in the treatment of streptococcal pharyngo-tonsillitis.

The inadequate penetration of penicillins into the tonsillar tissues and tonsillar surface fluid and microbiologic interactions between Group A beta-hemolytic streptococci (GABHS) and other pharyngo-tonsillar bacterial flora can account for their failure in eradicating GABHS pharyngo-tonsillitis (PT). These interactions include the presence of beta-lactamase producing bacteria (BLPB) that "shield" GABHS from penicillins, the absence of bacteria that interfere with the growth of GABHS, and the coaggregation between GABHS and Moraxella catarrhalis. In the treatment of acute tonsillitis, the use of cephalosporins can overcome these interactions by eradicating aerobic BLPB, while preserving the potentially interfering organisms and eliminating GABHS. In treatment of recurrent and chronic PT, the administration of clindamycin or amoxicillin-clavulanatecan eradicates both aerobic and anaerobic BLPB, as well as GABHS.