beta-Lactamase-producing bacteria recovered after clinical failures with various penicillin therapy.

The presence of beta-lactamase-producing bacteria in clinical specimens was investigated in 185 children with orofacial or respiratory tract infections. All of these patients failed to respond to antimicrobial therapy, including penicillins, that was administered to 148 (80%) of them. beta-Lactamase-producing aerobic and anaerobic bacteria were detected in 75 (40.5%) of the 185 children. The beta-lactamase-producing strains included all 11 strains of the Bacteroides fragilis group, 30 (45.4%) of the 66 strains of Bacteroides melaninogenicus group, five (41.7%) of the 12 strains of Bacteroides oralis, and 41 (97.6%) of 42 strains of Staphylococcus aureus. All beta-lactamase-producing Bacteroides strains were resistant to penicillin as compared with the non-beta-lactamase-producing strains. Clinical cure was achieved after surgical drainage and a change in antimicrobial therapy in most of the patients. In treatment of orofacial and respiratory tract infections, the clinician should consider the presence of beta-lactamase-producing Bacteroides sp and S aureus as a possible cause of clinical failure with various penicillin therapies.