Abstract
Chromogenic members of the colon-group are not unknown. MacConkey 1 listed yellow colon-group liquefiers from horse feces, pond water, rain water, roof washings, oats, beans, malt and ears of corn, and he reported a yellow B. coli communis from rain water. Rogers, Clark, and Lubs 2 reported that but few grain cultures are without pigment, many being decidedly chromogenic. They stated that this property is correlated with other characters and consequently is of value in classification. In a collection of colon-bacteria from human feces they found chromogenesis almost entirely absent. All their fecal cultures gave a faint yellow color but this was so slight and showed so little variation that it was of no value in differentiation. They did state, however, that there were a few exceptions to this rule. Wood 3 reported that 7 of 20 colon-group strains isolated from grains, hay and dried eggs and milk produced yellow pigment. In his Pocomoke river series Perry 4 encountered 5 cultures of aërobic, non-sporulating bacteria producing gas from lactose which produced a distinct yellow pigment. He excluded these chromogenic strains from consideration as fecal coli.
On January 14, 1936, a fecal specimen was received for study. Although the patient complained of certain general symptoms none referred to the gastro-intestinal tract and the analysis was under-taken as part of a routine rather than as an indicated procedure. A suitable saline suspension was at once prepared and adequately plated on citrated agar, blood agar, and Endo's agar. A small bit of the stool was placed in a large tube containing 30 cc. of lactose-indicator-broth. In this enriched medium typical acid- and gas-formation was observed in 24 hours. No colonies appeared on the citrated agar although it was heavily inoculated.
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