Antimicrobial susceptibility patterns (antibiograms) as an aid in differentiating Citrobacter species.
The hydrogen sulfide-negative Citrobacter group represents a taxonomic problem. Various investigators have proposed such designations as Padlewskia, Levinea, atypical Enterobacter cloacae, H2S-negative variants of Citrobacter, Citrobacter koseri and Citrobacter diversus. This problem has been investigated with emphasis on antibiograms as a means of discrimination. Clinical isolates fitting the designation Citrobacter were studied and, using the criteria of Ewing and Davis, separated into two groups: C. diversus (40 strains) or C. freundii (25 strains). Susceptibilities to ampicillin, carbenicillin, cefazolin, cephaloridine and cephalothin were determined by the agar-dilution method. C. diversus strains were resistant to 8 mug/ml ampicillin (97.5%) and 32 mug/ml carbenicillin (87.5%), and were susceptible to 8 mug/ml cephalosporins (greater than or equal to 90%). C. freundii strains were moderately susceptible to 8 mug/ml ampicillin (25%) and susceptible to 8 mug/ml carbenicillin (92%), and were resistant to 8 mug/ml cephalosporin (greater than or equal 92%). Using these data one can separate C. diversus from C. freundii with 90% accuracy.
D000667:Ampicillin / Q000494:pharmacology; D002228:Carbenicillin / Q000494:pharmacology; D002437:Cefazolin / Q000494:pharmacology; D002509:Cephaloridine / Q000494:pharmacology; D002512:Cephalothin / Q000494:pharmacology; D002954:Citrobacter / Q000145:classification* / Q000187:drug effects; D004755:Enterobacteriaceae / Q000145:classification*; D008826:Microbial Sensitivity Tests; D013045:Species Specificity
D000667:Ampicillin; D002228:Carbenicillin; D002437:Cefazolin; D002509:Cephaloridine; D002512:Cephalothin