Recent Experiences in the Rapid Identification of Bacterium coli Type I.

SUMMARY: When using MacConkey broth medium incubated at 44° as a confirmatory test for Bacterium coli Type I, positive reactions were produced by anaerobic lactose-fermenting bacteria such as Clostridium welchii. The use of brilliant green bile broth instead of MacConkey broth was completely successful in suppressing the growth of these organisms at 44°, but did not influence the growth of Bact. coli Type I. Two other coliform organisms, namely, Irregular Type II and Irregular Type VI were found to ferment lactose at 44°. A rapid test for their differentiation from Bact. coli Type I has been based upon the ability of that organism to produce indole at 44°, whereas the two irregular types are indole negative. By subculture of presumptive positive tubes in brilliant green bile broth and peptone water together with incubation at 44°, an estimation of the Bact. coli content of a water sample may be obtained within 48 hr. of primary inoculation.