Relative frequency of B. coli communior in contaminated water

Abstract

Some recent work of my students has been interesting in connection with the relative frequency of occurrence of the species of the B. coli group in water contaminated with human feces. The B. coli group consists of four species: B. communior (Durham), B. communis (Escherich), B. aerogenes (Escherich), B. acidi lactici (Hueppe). The general characteristics common to all species are: short, Gram-negative, cocco-bacilli, with rounded ends, non-spore bearing, fermentation of dextrose, glucose and lactose with gas production, non-liquefaction of gelatin after 14 days, indol production, and reduction of nitrates to nitrites. In general, also, litmus milk is acidified and coagulated. Further differentiation of the members of the group is possible by means of fermentation tests in the sugars dulcite, saccharose, mannite and raffinose. B. communior and B. communis ferment dulcite; B. aerogenes and acidi lactici do not. B. communior and B. aerogenes ferment saccharose. B. communis and B. acidi lactici do not. MacConkey 1 isolated a large number of strains of these species from feces and found that their relative frequency was as follows:

Graham Smith 2 in the analysis of thirty-five strains isolated from flies found, on the other hand, a predominance of communior (43 per cent.), communis occurring much less frequently (17 per cent.). B. aerogenes (11 per cent.) and B. acidi lactici (29 per cent.) did not differ greatly in their occurrence.

Winslow and Walker 3 in twenty-five strains isolated from feces found 28 per cent. of communior, 60 per cent. communis, 4 per cent. aerogenes, and 8 per cent. acidi lactici.

The results of an analysis of thirty-two strains isolated in my laboratory from human feces were as follows:

The saccharose fermenting species, then, may predominate in water recently contaminated with human feces.