Coli‐aerogenes Bacteria From Farm Dairy Equipment and Raw Milk

Abstract

SUMMARY: A series of 1,040 cultures of coli‐aerogenes bacteria isolated at 30° from farm dairy equipment and raw milk was classified according to the recommendations of the Coliform Sub‐Committee of the Society for Applied Bacteriology (Report, 1949). The distribution of species and types isolated from milk did not differ materially from that for dairy equipment, Klebsiella cloacae, K. aerogenes and Citrobacter freundii being the dominant species, while the incidence of Escherichia coli was relatively low. There was no marked seasonal incidence of any type, though E. coli I formed a slightly higher proportion of the coli‐aerogenes microflora in winter, whereas K. aerogenes I was slightly higher in summer. Many of the cultures of the dominant types, K. cloacae, K. aerogenes I and Cit. freundii I, did not form acid and gas from lactose in two days at 37°. Consequently 37° negative, anaerogenic and paracolon strains constituted a relatively high proporton (49%) of the coli‐aerogenes microflora.

Coli‐aerogenes Bacteria in Farm Water Supplies

“…Thus the formation of acid and gas in MacConkey's broth at 37" and at 44" is retained aa the essential criterion for the determination of the coliaerogenes and E. coli I contents respectively in the assessment of the sanitary quality of water in Britain (Report, 1956a). However, incubation at 30" is used in England and Wales for the routine enumeration of coli-aerogenes bacteria in milk and milk products, where 'low temperature' strains of Klebsiella and Citrobacter are among the most active spoilage organisms (Thomas, 1955; Thomas, Hobson t Elson, 1958).…”

Psychrotrophic Coli‐aerogenes Bacteria in Refrigerated Milk: A Review

“…It has been recognized in Brtain for many years that strains not fermenting at 37" constitute a relatively high proportion of the coli-aerogenes microflora of raw milk (Mattick & Hiscox, 1935), and since 1950 the presence of coliforms in milk, milk products and rinses of farm dairy equipment has been determined at advisory laboratories in England and Wales by incubation of McConkey's broth at 30" for 72 h or Violet Red-Bile Agar at 30" for 20-24 h. A rather similar procedure with incubation at 30 " has recently been incorporated in International Standards promulgated by the International Dairy Federation (1966a, 6 ) . In this connection, it is of interest to observe that of 1040 strains of coli-aerogenes bacteria isolated at 30" from farm dairy equipment and farm milk supplies by Thomas, Hobson & Elson (1958), 49% failed to form gas in lactose broth at 37" within 48 h, while 63% of the 321 strains of K. cloacae were 37" negative.…”

The Significance of Various Organisms of Faecal Origin in Foods and Drinking Water

“…(i) Coli-aerogenes tests. The determination of the most probable numbers of coliaerogenes bacteria in foods using enrichment methods in liquid media is of limited value because it has become increasingly apparent that the technique has three essential shortcomings : a very high coefficient of variation ; a limited reliability due to bacterial antagonism (Habs & Langeloh, 1960) and synergism ; and the impossibility of detecting anaerogenic types which nevertheless occur quite frequently (Thomas, Hobson & Elson, 1958).…”