Plasmid encoded beta-lactamases resistant to inhibition by clavulanic acid produced by calf faecal coliforms
Hunter, J.E.; Corkill, J.E.; McLennan, A.G.; Fletcher, J.N.; Hart, C.A.
Research in Veterinary Science 55(3): 367-370
1993
ISSN/ISBN: 0034-5288 PMID: 8284502 Document Number: 421029
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 characterized. 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 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.