Role of bacterial interference and beta-lactamase-producing bacteria in the failure of penicillin to eradicate group A streptococcal pharyngotonsillitis.

OBJECTIVE

To determine the association among bacterial interference and beta-lactamase production and penicillin failure in treating streptococcal pharyngotonsillitis.

DESIGN

Fifty-two children who had acute pharyngotonsillitis caused by group A beta-hemolytic streptococci (GABHS) were treated for 10 days with penicillin. Surface tonsillar cultures were obtained before therapy and at 10, 21, and 42 days after termination of therapy. The cultures obtained before and 10 days after completion of treatment were processed for aerobic and anaerobic organisms; the other cultures were processed for GABHS only.

RESULTS

Based on eradication of GABHS, 38 patients were in the classification bacteriologic "cure"; 14 were in the classification bacteriologic "failure" after therapy. In the cured group, before therapy alpha-hemolytic streptococci inhibiting their own GABHS were recovered in the cultures of 14 children (37%), and beta-lactamase-producing organisms (BLPB) were detected in the cultures of two children (5%). After therapy, inhibiting alpha-hemolytic streptococci were recovered in 31 cultures (82%), and BLPB were detected in five cultures (13%). In contrast, in the failure group, before therapy alpha-hemolytic streptococci were isolated in one culture (7%) and BLPB were recovered from nine cultures (64%). After therapy, alpha-hemolytic streptococci were recovered in four cultures (29%), and BLPB was recovered in 13 cultures (93%).

CONCLUSIONS

These data show that the absence of interfering alpha-hemolytic streptococci and the presence of BLPB is associated with penicillin failure in the treatment of GABHS pharyngotonsillitis.