Some observations on the influence of the micro-environment on loss of M substance in strains of Streptococcus pyogenes

Abstract

1. An M-producing strain of Streptococcus pyogenes type-12 was shown to be carried on the surface of apparently healthy tonsils for at least 3 years.2. Loss of M substance in a strain of type-3 in a tonsillar carrier was shown to be by gradual replacement of matt forms by glossy variants. This pair of naturally occurring variants showed very different growth rates as mixtures in liquid media.3. Under suitable conditions, glossy variants regularly appeared and replaced the M-producing strain from which they were derived in these and all other strains of type-3 and type-12 tested from a wide variety of sources.4. It is suggested that the selection of variants by the differential nutrient value of the micro-environment is the deciding factor in carrier strains showing loss of M substance.