Beta-lactamase-producing bacteria in mixed infections.

Beta-lactamase-producing bacteria (BLPB) can play an important role in polymicrobial infections. They can have a direct pathogenic impact in causing infections, as well as an indirect effect through their ability to produce the beta-lactamase. BLPB may not only survive penicillin therapy themselves, but can also protect other penicillin-susceptible bacteria from penicillin by releasing free beta-lactamase into their immediate environment. This phenomenon occurs in upper respiratory tract, skin, soft tissue, surgical and other infections. The in-vitro and in-vivo clinical evidence supporting the role of BLPB in the increasing failure of penicillin to resolve such infections, and the implications of this phenomenon for the management of infections, are discussed.