Association of penicillin-tolerant streptococci with epidemics of streptococcal pharyngitis in closed communities.

The association of penicillin-tolerant streptococci with reported epidemics of streptococcal pharyngitis in Israel was studied. The streptococcal strains had been isolated during 11 epidemics of community-acquired pharyngitis and 6 food-borne epidemics of pharyngitis occurring in the last 15 years. Strains were stocked lyophilized. Isolates were defined as tolerant if the MBC/MIC ratio for penicillin was greater than or equal to 32. All 122 group A streptococcal strains isolated during the epidemics of community-acquired infection showed tolerance to penicillin. In contrast, none of the 52 strains from food-borne epidemics (24 group A, 18 group C and 8 group G) was tolerant.