ANTIBIOTICS PRODUCED BY MICROCOCCI AND STREPTOCOCCI THAT SHOW SELECTIVE INHIBITION WITHIN THE GENUS STREPTOCOCCUS

Abstract

Two strains of Micrococcus epidermidis and five of Micrococcus pyogenes were found to produce antibiotics that were detected by using a mucoid Streptococcus pyogenes as test organism. The antibiotics were also active against some other Gram-positive organisms, but not against Gram-negative bacteria. The M. epidermidis strains inhibited most β-haemolytic streptococci with the exception of mucoid Lancefield Group C. The M. pyogenes strains were active against the majority of mucoid S. pyogenes (Group A), but few or none of the nonmucoid strains were inhibited. Streptococci of Groups B, C, and G were not affected. On the basis of antibacterial spectrum and characteristics of the antibiotics (dialysis, stability, and production curves) the seven strains were divided into four groups producing antibiotics of different types.Three strains of β-haemolytic streptococci were tested which were known to produce antibiotics. Two of these showed a selective inhibition similar to the micrococci. They inhibited all of the mucoid S. pyogenes but few of the nonmucoid; they inhibited all strains of Group C, both mucoid and nonmucoid, but did not inhibit the Group G strains tested.These observations suggest that, apart from capsulation, there may be a fundamental metabolic difference between the majority of mucoid and nonmucoid strains of S. pyogenes.