Abstract
From one of the variants (C16) obtained by Nungester and Anderson 1 in a study of a recently isolated B. coli-like organism, Nungester 2 has in later work obtained 7 additional variants. These agglutinate in similar high dilutions of the parent immune serum but differ from each other in their reactions on lactose, maltose and sucrose Andrade agar as indicated in the table.
In carbohydrate broth medium 2 types of reactions occurred: (1) in broths containing the same kind of sugars as in the indicator plates which gave positive reactions, acid was produced in one day; (2) in broths containing the same kind of sugars as in the indicator plates which gave negative reactions, acid production was delayed and appeared after one to 10 days.
Jones, Orcutt and Little 3 have reported atypical slow lactose fermenting colon bacilli which appear somewhat similar to those described above. Alkalinity was maintained in broth for several days before acid was evident. In all cases, however, quantitative analysis showed that lactose was being consumed from the first day of growth. The authors postulate that although lactose is used from the start, sufficient alkali is produced to mask the fermentation.
It therefore seemed advisable to determine whether the same mechanism was operative in the case of C16 and its variants or whether this delay in acid production corresponded to a postponement of sugar utilization. For this purpose, two basic mediums were used: (1) sugar-free beef infusion broth and (2) 2% peptone 0.5% sodium chloride solution. To each was added 10% lactose or maltose solution, sterilized by filtration, to make a final concentration of about 0.8%. These mediums were then tubed (10-15 cc. per tube), incubated several days for sterility, and inoculated either from agar slants or from 24-hour carbohydrate indicator agar plate cultures.
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