120. The Types Of Coliform Bacteria in Bovine Faeces

Abstract

1. In an examination of the coliform flora of 114 specimens of bovine faeces, 342 cultures of coliform bacteria were isolated by the ordinary methods.Of the cultures obtained, 330 (or 96·4 per cent.) were typicalBact. coliandonly twelve (or 3·5 per cent.) were ofBact. aerogenes, Bact. cloacaeand other Koser-positive types. The most prevalent types ofBact. coliwere MacConkey's B, No. 71 orBact. coli communior(185 cultures or 56 per cent.), MacConkey's B, No. 34, orBact. coli communisEscherich (sixty-nine cultures or 20·9 per cent.), and MacConkey's B, No. 1 (twenty-three cultures or 6·9 per cent.).

The classification of coliform bacteria

“…They are also the most prevalent forms in milk (see Table II), their presence being due to direct or indirect contamination with faeces (Malcolm, 1933). While 882 of the 1636 cultures isolated from milk and bovine faeces (see Table I) were B. coli types, the number would have been much greater but for the fact that with the last hundred faecal specimens, methods of isolation were employed suitable for the enrichment of Koserpositive types, and all B. coli cultures obtained from these specimens were discarded.…”

“…The faecal cultures were obtained by brilliant green and other enrichment methods of isolation (Malcolm, 1935). It would therefore appear that such types are of comparatively rare occurrence in faeces and in milk.…”

“…108) and B. oxytocus perniciosus (MacConkey's type no. 65), fail to liquefy gelatin even after prolonged incubation (Malcolm, 1933(Malcolm, , 1935. Also, misleading results may be obtained under such conditions owing to the liquefaction being due merely to the action of endo-proteases which have been liberated from the dead bacterial cells (Committee on Bacteriological Technic of the Society of American Bacteriologists, 1934).…”

Distribution of coliform organisms in milk and the accuracy of the presumptive coliform test

“…Wilson (1935, p. 156) found that 70% of coli strains, 47 % of aerogenes, 84 % of cloacae and 44 % of intermediate strains were motile. Malcolm (1935), investigating 595 strains, finds the following proportions of motile strains: coli 88 %, aerogenes 11 %, cloacae 90 % and 65% intermediate. Chalmers (1928) also finds the majority of coli strains motile and the reverse true of aerogenes types.…”

“…Wilson (1935) finds that in raw milk the coli, intermediate and aerogenes-cloacae groups were present in about equal proportions. Malcolm (1933) isolated strains of coliform organisms from market milk in summer and winter periods and found that coli types were 40 % in summer and 71 % in winter, while aerogenes types fell from 22 % in summer to 7 % in winter. This evidence suggests that the majority of coliform organisms in raw milk are likely to be motile and that clumping is unlikely to take place.…”