TEM-103/IRT-28 β-Lactamase, a New TEM Variant Produced by Escherichia coli BM4511

Clinical isolate Escherichia coli BM4511 was resistant to broad-spectrum penicillins in the presence or in the absence of β-lactamase inhibitors but remained susceptible to cephalosporins. Resistance was due to production of a new TEM-type β-lactamase, designated TEM-103/IRT-28, characterized by the Arg(275)Leu substitution and encoded by the ca. 62-kb pIP845 conjugative plasmid of the IncI1 incompatibility group.