Biochemical and antibiotic susceptibility studies of H2S-negative Citrobacter.

Ninety-four strains of H(2)S-negative Citrobacter were biochemically characterized and their antibiograms were determined. The antibiograms demonstrated not only a difference from Enterobacter cloacae but also a difference within the Citrobacter group between the indole-negative and indole-positive strains. These differences were statistically significant and emphasize the importance of the indole reaction as an aid to speciation of the H(2)S-negative Citrobacter.