54 



Scientific Proceedings (51). 



39 (735) 



Relative frequency of B. coli communior in contaminated water. 



By J. G. Fitzgerald. 



[From the Hearst Laboratory of Pathology and Bacteriology, 

 University of California.] 



Some recent work of my students has been interesting in con- 

 nection 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 



1 MacConkey, Journal Hygiene, 1905, Vol. 5, p. 333. 



2 Graham-Smith, Report of Local Government Board, London, 1909. 



3 Winslow and Walker, Science, 1907, Vol. 26, p. 675. 



Per Cent. 



B. communior. 

 B. communis . 

 B. aerogenes. . 

 B. acidi lactici 



37 

 15 

 25 



