B. colias an Index of Faecal Pollution of Water Supplies

Abstract

THE quantitative determination of B. coli in a given sample of water has long been accepted as affording a good measurement of the probability of recent contamination with excreta.The systematist uses the term B. coli to define a single definite type; but the sanitary bacteriologist, who is not concerned with botanical classifications, places a much broader interpretation upon it and includes a whole group of organisms under this heading; yet most workers agree that a bacillus of this class should have the following characteristics-a short bacillus with rounded ends, Gram negative, non-sporing and a facultative anaerobe. It should ferment lactose and dextrose with the production of acid and gas, give a clot in milk, fail to liquefy gelatine, and produce indol in a medium containing peptone.It has been known for some time that organisms of the B. coli group may be present in soil and on grain where there has been little apparent opportunity for faecal pollution, and recent investigations have yielded evidence indicating that certain cultural reactions are highly correlated with different natural habitats. It has therefore become possible, by the use of laboratory tests, to assign an excretal or non-excretal origin to a given strain of B. coli with a reasonable degree of probability.Early conceptions of B. coli.Bacilli of the colon group were first isolated in 1885 by Escherich in the course of his investigations on the organisms in the faeces of young children. He described B. coli as a Gram negative bacillus producing characteristic colonies on gelatine, agar and potato, coagulating milk, and forming gas in glucose.Several bacteriologists, including Dyar and his co-workers (1894)-who used the cultural characteristics on agar, gelatine and potato, the reduction of nitrates and the clotting of milk as differential tests-have shown that B. coli is normally present in the intestines of goats, pigs, rabbits and other animals; and Kruse (1894) pointed out that the term "B. coli" applies not to a single type but to a whole group of organisms which is very widely distributed.Laurent (1899), while investigating certain diseases of potato, noted the occurrence of a bacillus which on testing proved to be of the colon type-a facultative anaerobe, incapable of liquefying gelatine, but able to reduce nitrates, produce a clot in milk and give acid and gas in glucose and in lactose broth. He cultivated these organisms on plants which had received large amounts of chalk, and also on potatoes which had been immersed in alkaline solution, and he found that B. coli tended to become parasitic when the resistance of the tubers had been artificially reduced in this way.

68. The Occurrence of Coliform Bacteria in Milk

“…A large proportion (94 out of 133) of the exceptions gave negative Voges-Proskauer and negative indole reactions. According to Koser and others, strains of this type are common in soil and water but are rare in faeces (3,6,7,8,9). The Koser reaction showed a very much higher degree of association with the indole reaction, the coefficient of association between the two reactions being -0-9905.…”

Coli-aerogenes Differentiation in Water Analysis

“…aerogenes (----H +) the majority of them remain unchanged. Such strains have been reported isolated from soil by (1926) anid from water by Bardsley (1926) Raghavachari (1926) and Lewis and Pittman (1928). We have found these strains extremely rare in human and animal feces (see table 12).…”

“…This led to confusion' in interpretation of the results obtained with it in water laboratories. Bardsley (1926) in England used this test in conjunction with the M.R., V.P. and indol tests and, apparently, because it failed to correlate as expected with these tests, dropped the citrate test as the least valuable.…”

“…Nevertheless the indol test is still used and considered important by Houston (1928). Bahlman and Sohn (1924), Bardsley (1926) and Lewis and Pittman (1929) all used the indol test in conjunction with other tests with interesting results which we will discuss later.…”

The Occurrence of Coli‐aerogenes Organisms on Plants

“…For this reason they have been referred to frequently as 'non-faecal' or 'vegetation' types of coli-aerogenes bacteria. Aerobacter types, however, are apparently capable of a commensal existence as they have been found to be present normally in the human and animal intestine and in faeces (Ford, 1927;Cruickshank & Cruickshank, 1931 ;Hay, 1932 ; Bardsley, 1926;Sherman, 1935;Malcolm, 1938), but in smaller numbers thin Escherichia so that enrichment methods may be necessary for their isolation.…”