Studies on Inhibition, Attenuation, and Rejuvenation of Bacillus Coli.

Elements of Water Bacteriology: with Special Reference to Sanitary Water Analysis

“…organisms other than B. coli by bile may both be obtained as pointed out above by inoculating lactose bile from THE COLON GEOUP OF BACILLI 129 the dextrose broth.Haleand Melia (1910) find that this gives results in as high a dilution as by the use of dextrose broth and with the clear-cut results of lactose bile.On the whole we do not think it has been shown that aesculin has sufficient differential value to warrant its inclusion in enrichment media to be used inthe colon test. It appears that the anaerobic B. welchii is practically the only form outside the colon group which produces a characteristic reaction in lactose bile and not in aesculin-bile salt media.…”

“…On the other hand, the high numbers of other bacteria present make the danger of overgrowths particularly great. With waters of fair quality, such as those with which we ordinarily deal in sanitary water analysis, lactose bile is open to the same objection as phenol broth and the Eijkman test though in less degree.It inhibits not only the overgrowing forms but the weaker representatives of the B. coli group itself, and the net effect is to diminish positive results.Haleand Melia (1910) inoculated unsterilized water (shown to contain no gas formers) with a pure culture of B. coli and stored it for different periods and under Comparison of presumptive tests with plate counts on litmus-lactose agar showed that a gas test in dextrose broth corresponded to an average of 4 bacteria and a positive test in lactose bile to 39 bacteria.…”