Characterization of bacteroides melaninogenicus

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Abstract
Human isolates of B. melaninogenicus, 42 from a variety of clinical infections and 16 from normal flora, were studied for pigment production and UV light fluorescence and by 40 biochemical and other tests, including end-product analysis by GLC. In several instances, tests were repeated several times and the results were reproducible. Agar plate dilution susceptibility tests were also performed to 12 antimicrobial agents. These 58 strains could be reliably placed into 3 groups, corresponding to the 3 subspecies described [B. melaninogenicus ssp. asaccharolyticus, B. melaninogenicus ssp. intermedius, B. melaninogenicus ssp. melaninogenicus], based on 7 characteristics. These included acid production in peptone yeast glucose medium, production of n-butyric acid from peptone yeast glucose medium, esculin hydrolysis, starch hydrolysis, indole production, effect on milk and lipase production. Production of H2 in peptone yeast fructose medium may be another distinguishing characteristic. Generally there was not much difference in the susceptibility of the 3 groups to the various antimicrobial agents tested. Two strains had a minimal inhibitory concentration of penicillin G of 16 and 32 U[units]/ml, respectively. Three strains did not produce a black pigment despite prolonged incubation on blood-containing media.