The isolation of streptococci from human faeces

Three 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. faecalis and S. mitior were each found in over half the samples. Lancefield group B and G streptococci, S. bovis II, an atypical strain of S. bovis I, S. cremoris, S. durans and a dextran-positive strain of S. mitior were 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 X 10(3)-3 X 10(8) (geometric mean 7 X 10(5)) per g. The significance of these findings is discussed.