Blackwell Publishing Journal Backfiles 1879-2005
Abstract LXA-1, a novel plasmid-mediated β-lactamase, was observed in clinical isolates of Klebsiella oxytoca, Klebsiella pneumoniae, Citrobacter freundii and Enterobacter cloacae. All the strains additionally produced TEM-1 β-lactamase. LXA-1 had an Mr of 24 000 and a pI of 6.7. It hydrolysed benzyl-penicillin, ampicillin, carbenicillin and first generation cephalosporins, but not methicillin, oxacillin or cefotaxime. Clavulanate and cloxacillin were inhibitors. Studies of one of the E. cloacae isolates showed that LXA-1 was encoded by a 41-MDa IncFII plasmid distinct from that encoding TEM-1 enzyme in the strain. Transconjugants which acquired LXA-1 production, but not TEM-1, exhibited only low-level resistance to substrate β-lactams.
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