Published online by Cambridge University Press: 15 May 2009
Since the original definition of the coli-aerogenes group of organisms by MacConkey (1905,1909), research has been continually directed in an endeavour to find a more rapid and definite distinction between its respective members.
In general, for the purposes of water analysis, the conform organisms can be divided into two main groups: faecal coli, of which Bact. colitype I can be considered the typical member, and the non-faecal organisms comprising the intermediate-aerogenes-cloacae (I.A.C.) organisms. All available evidence tends to show that Bact. colitype I is by far the most frequent organism in the human and animal intestine. Levine (1921) has summarized the figures of various workers and obtained a percentage ratio of 93·4:6·6 as the ratio of coli:aerogenes in faeces, while Bardsley (1938) has shown that in only a very few cases does the number of I.A.C. organisms exceed the faecal coli in faeces.