Failure of penicillin to eradicate group A streptococci during an outbreak of pharyngitis.

In an outbreak of group A streptococcal pharyngitis in a semi-closed community, 42 (25%) of 169 courses of antibiotic therapy failed to eradicate the organism. 16 (19%) of 85 individuals treated with intramuscular benzathine penicillin G and 9 (19%) of 47 patients treated with an oral antibiotic (penicillin V or erythromycin) continued to harbour the same serotype of group A streptococcus. 12 (48%) of 25 persons remained treatment failures after re-treatment; even after a third course of treatment 5 of 12 (42%) still harboured the organism. Neither antibiotic resistance of the epidemic strain nor reacquisition of the organism from contacts could be implicated as causes. The data suggest that many who did not respond to treatment were streptococcal carriers and raise the possibility that it is more difficult to eradicate the organism from the carrier than from the acutely infected individual.