title: Plasmid encoded beta-lactamases resistant to inhibition by clavulanic acid produced by calf faecal coliforms.
abstract: Two new plasmid encoded beta-lactamase enzymes produced by a strain of Escherichia coli and a strain of Citrobacter freundii isolated from calf faeces have been characterised. Both enzymes were similar to TEM-1 in terms of substrate and inhibition profiles and physical properties but differed from TEM-1 in being far less susceptible to the beta-lactamase inhibitors clavulanic acid or tazobactam. In each case transfer of the plasmid E coli K12 rendered it clinically resistant to the combination of amoxycillin and clavulanic acid. The beta-lactamase from the E coli had an iso-electric point (pI) of 5.4 and was encoded on a plasmid of 95 Kbp which also mediated resistance to tetracycline, sulphonamides, apramycin, streptomycin and gentamicin. The beta-lactamase from the C freundii had a pI of 5.2 and was encoded on a 75 Kbp plasmid which also mediated resistance to trimethoprim, chloramphenicol, apramycin, gentamicin and tobramycin.
authors.affiliation: Department of Medical Microbiology, University of Liverpool.
authors.forename: J E
authors.initials: JE
authors.lastname: Hunter
authors.forename: J E
authors.initials: JE
authors.lastname: Corkill
authors.forename: A G
authors.initials: AG
authors.lastname: McLennan
authors.forename: J N
authors.initials: JN
authors.lastname: Fletcher
authors.forename: C A
authors.initials: CA
authors.lastname: Hart
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology; D019980:Amoxicillin-Potassium Clavulanate Combination; D000818:Animals; D002417:Cattle / Q000382:microbiology*; D016971:Citrobacter freundii / Q000201:enzymology / Q000302:isolation & purification; D002969:Clavulanic Acids / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D004755:Enterobacteriaceae / Q000201:enzymology*; D004926:Escherichia coli / Q000201:enzymology / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D011815:R Factors; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D002969:Clavulanic Acids; D065093:beta-Lactamase Inhibitors; D019980:Amoxicillin-Potassium Clavulanate Combination; D000658:Amoxicillin; D001618:beta-Lactamases