Role of beta-lactamase-producing bacteria in the failure of penicillin to eradicate group A streptococci.

Ninety-eight children who had acute tonsillitis due to Group A beta-hemolytic streptococci were treated for 10 days with orally administered penicillin B, potassium. Surface tonsillar cultures were obtained before therapy, at the end of therapy and 10, 21 and 42 days after termination of therapy. The cultures obtained before and after completion of treatment were processed for aerobic and anaerobic organisms, while the other cultures were processed only for Group A beta-hemolytic streptococci. On the basis of bacteriologic results 62 patients were considered "cured" (Group A) and 36 "failed" (Group B) following therapy. Before therapy 18 isolates of beta-lactamase-producing organisms (BLPO) were detected in 16 (26%) children in Group A; after therapy 30 BLPO were detected in 19 (30%) children. In contrast, before therapy 40 BLPO were recovered from 25 (69%) children in Group B; this number increased to 62 BLPO in 31 (86%) of those children. The study demonstrates an association between failure to eradicate Group A beta-hemolytic streptococci and the presence of aerobic and anaerobic BLPO.