title: Mutants of the TEM-1 beta-lactamase conferring resistance to ceftazidime.
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.
authors.affiliation: Department of Bacteriology, Medical School, University of Edinburgh, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Payne
authors.forename: M S
authors.initials: MS
authors.lastname: Marriott
authors.forename: S G
authors.initials: SG
authors.lastname: Amyes
mesh_terms: D002442:Ceftazidime / Q000494:pharmacology*; D003227:Conjugation, Genetic; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D007525:Isoelectric Focusing; D007700:Kinetics; D007709:Klebsiella / Q000201:enzymology / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009154:Mutation; D011815:R Factors; D014556:Urine / Q000382:microbiology; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D002442:Ceftazidime; D001618:beta-Lactamases