Novel, plasmid-encoded, TEM-derived extended-spectrum beta-lactamase in Klebsiella pneumoniae conferring higher resistance to aztreonam than to extended-spectrum cephalosporins

Abstract

A clinical isolate of Klebsiella pneumoniae was more resistant to aztreonam than to cefotaxime and ceftazidime. It produced a clavulanate-susceptible beta-lactamase with an isoelectric point of 6.3 which readily hydrolyzed penicillins, cefotaxime, and ceftazidime, but which hydrolyzed aztreonam poorly. The enzyme was encoded by a gene on a 15-kb plasmid; the gene hybridized with an intragenic DNA probe of blaTEM.