Citrobacter diversus ULA27 produces two forms of a chromosomal beta-lactamase

J Antimicrob Chemother. 1987 Jul;20(1):23-35. doi: 10.1093/jac/20.1.23.


A multi-resistant clinical isolate of Citrobacter diversus, particularly resistant to penicillins and cephalosporins, has been studied. The strain produced constitutively high levels of beta-lactamase which efficiently hydrolysed cephaloridine but not ampicillin. The apparent Km value for cephaloridine (125 +/- 25 microM) was within the range usually observed for beta-lactamases in similar bacteria. The strain possessed two forms of the enzyme as indicated by isoelectric focusing patterns, HPLC analysis and two pH optima. SDS-PAGE analysis indicated a single protein responsible for both forms. The strain possessed a single plasmid, as revealed by agarose gel electrophoresis, but beta-lactamase production was not plasmid encoded. The available data indicate the beta-lactamase(s) of C. diversus ULA27 to be chromosomally encoded.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Chromatography, High Pressure Liquid
  • Citrobacter / drug effects
  • Citrobacter / enzymology*
  • Citrobacter / genetics
  • Drug Resistance, Microbial / genetics
  • Electrophoresis, Polyacrylamide Gel
  • Genetic Code
  • Isoelectric Focusing
  • Molecular Weight
  • beta-Lactamases / analysis*
  • beta-Lactams


  • Anti-Bacterial Agents
  • beta-Lactams
  • beta-Lactamases