A Study of the Identity, Distribution and Survival of Faecal Streptococci in Polluted Watercourses

Abstract

A study of the faecal streptococci of the River Blythe (West Midlands) was undertaken and the relevant literature was reviewed. Methods for the routine identification and separation of Streptococcus faecalis were investigated and the following tests were considered to be the most valuable and reliable in relation to maximum efficiency and minimum effort: growth in 0.04% potassium tellurite, growth at 50°C, triphenyltetrazolium chloride reduction in liquid medium at pH 6.0, acid production from citrate, glycerol and melezitose, and tyrosine decarboxylation. The efficiency of four different media used for the recovery of faecal streptococci from various sources was investigated and the Slanetz and Bartley medium (1957) was found most favourable. The river under study was sampled regularly at nine stations over a period of one year. Counts on Slanetz and Bartley medium were made and 169 isolates obtained. Only 15 of these were S. faecalis, 30 were considered to be Streptococcus bovis/Streptococcus equinus and the rest were Streptococcus faecium. The low incidence of S. faecalis suggests that pollution by farm animals is more significant than human faecal pollution in this river. No Streptococcus avium strain was isolated. To assist in the interpretation of this data, the survival in flowing water of the different species of faecal streptococci and Escherichia coli was tested in artificial streams. All strains survived longer at low than at high temperatures. S. bovis died out most rapidly followed by E. coli. Survival in S. faecium and S. faecalis was similar; both survived longer than E. coli. A numerical taxonomy of the river isolates together with 12 reference cultures and 16 isolates from horse, cow and human faeces was carried out. S. faecalis formed a cluster separate from that formed by S. faecium, S. bovis and S. equinus. The significance of the results obtained was discussed in relation to existing ideas.