Mutants of the TEM-1 beta-lactamase conferring resistance to ceftazidime

J Antimicrob Chemother. 1989 Aug;24(2):103-10. doi: 10.1093/jac/24.2.103.

Abstract

Spontaneous ceftazidime resistant mutants were obtained from an Escherichia coli K12 J62-2 expressing the TEM-1 beta-lactamase (mutation frequency = 10(-9). These mutants produced beta-lactamases with similar molecular weights, kinetic parameters and isoelectric points (pI) to the beta-lactamases produced by ceftazidime resistant clinical isolates which have recently been identified in this laboratory. Mutant enzyme A focused as a doublet band at pI 5.3 with an additional weak pI 5.4 band. The doublet co-focused with the TEM-E2 beta-lactamase, produced by a ceftazidime resistant Klebsiella oxytoca isolate, which was originally obtained in a Liverpool hospital. Mutant enzyme B had a pI identical to the TEM-E1 beta-lactamase produced by a ceftazidime resistant clinical isolate of E. coli found in Belgium. These results suggest that the two beta-lactamases in the clinical strains may have come from simple mutations of the TEM-1 beta-lactamase gene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ceftazidime / pharmacology*
  • Conjugation, Genetic
  • Drug Resistance, Microbial / genetics
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Humans
  • Isoelectric Focusing
  • Kinetics
  • Klebsiella / enzymology
  • Klebsiella / genetics
  • Microbial Sensitivity Tests
  • Mutation*
  • R Factors
  • Urine / microbiology
  • beta-Lactamases / genetics*

Substances

  • Ceftazidime
  • beta-Lactamases