The isolation of streptococci from human faeces

Abstract

SummaryThree selective media were designed for isolation of streptococci from faeces. Samples of faeces from twelve normal adults were suspended and serially diluted in saline or broth saline, and equal volumes of each dilution were spread and incubated on the media. The number of colonies of each different type which developed was counted and one colony of each type was subcultured and identified.Altogether, streptococci of 13 taxa were found.S. faecium, S. mutans, S. milleri, S. faecalisandS. mitiorwere each found in over half the samples. Lancefield group B and G streptococci,S. bovisII, an atypical strain ofS. bovisI,S. cremoris, S. duransand a dextran-positive strain ofS. mitiorwere each present in 1 or 2 samples. Individual samples contained 2–7 (mean 4·6) streptococcal taxa, and total viable counts of streptococci of 3 × 103−3 × 108(geometric mean 7 × 105) per g. The significance of these findings is discussed.