Antimicrobial susceptibility patterns (antibiograms) as an aid in differentiating Citrobacter species

Am J Clin Pathol. 1977 Feb;67(2):187-9. doi: 10.1093/ajcp/67.2.187.

Abstract

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.

MeSH terms

  • Ampicillin / pharmacology
  • Carbenicillin / pharmacology
  • Cefazolin / pharmacology
  • Cephaloridine / pharmacology
  • Cephalothin / pharmacology
  • Citrobacter / classification*
  • Citrobacter / drug effects
  • Enterobacteriaceae / classification*
  • Microbial Sensitivity Tests
  • Species Specificity

Substances

  • Ampicillin
  • Carbenicillin
  • Cefazolin
  • Cephaloridine
  • Cephalothin