Penicillin tolerance among Beta-hemolytic streptococci and production of the group carbohydrates, hemolysins, hyaluronidases and deoxyribonucleases

Abstract

Penicillin tolerance among 67 strains of beta-hemolytic streptococci was examined by determining the ratio of the minimal bactericidal concentration to the minimal inhibitory concentration as 32 or greater. Tolerance was demonstrated in 15 group A strains and in 11.7, and 4 of groups B, C and G, respectively. Thereafter the effects of a subminimal inhibitory concentration (1/2 MIC) of penicillin on the bacterial products of four tolerant and four nontolerant strains (two of each Lancefield group) were analyzed and compared. The antibiotic caused a marked increase in the expression of the group carbohydrates for strains of group B. Penicillin was found to reduce the cell-bound hemolysin activities of the four tolerant strains and to increase the activity of the other (free) form of nontolerant groups A, C and G hemolysins. Penicillin caused an increase in the extracellular hyaluronidase activities of one group A and groups B, C and G streptococci. With added antibiotic the production of deoxyribonuclease by tolerant groups A, C and G was greatly enhanced and that of the group B streptococcus was arrested.

Isolamento de Streptococcus pyogenes em indivíduos com faringoamigdalite e teste de susceptibilidade a antimicrobianos

“…Todas as cepas de S. pyogenes isoladas até o momento são sensíveis à penicilina, entretanto, algumas cepas apresentam tolerância a este antibiótico, isto é, para estas cepas a concentração mínima bactericida da penicilina é 32 vezes mais alta que a concentração mínima inibitória 14 . Falhas de tratamento têm sido associadas a dosagens inadequadas da penicilina durante o tratamento, e a presença de amostras de S. pyogenes tolerantes a penicilina ou com capacidade de para invadir células epiteliais onde permanecem protegidas da ação do agente antimicrobiano 4,15 .…”