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

P. M. Southern, M. K. Bagby

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


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 μg/ml ampicillin (97.5%) and 32 μg/ml carbenicillin (87.5%), and were susceptible to 8 μg/ml cephalosporins (≥90%). C. freundii strains were moderately susceptible to 8 μg/ml ampicillin (25%) and susceptible to 8 μg/ml carbenicillin (92%), and were resistant to 8 μg/ml cephalosporins (≥92%). Using these data one can separate C. diversus from C. freundii with 90% accuracy.

Original languageEnglish (US)
Pages (from-to)187-189
Number of pages3
JournalAmerican journal of clinical pathology
Issue number2
StatePublished - Jan 1 1977

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


Dive into the research topics of 'Antimicrobial susceptibility patterns (antibiograms) as an aid in differentiating citrobacter species'. Together they form a unique fingerprint.

Cite this