Transferable DHA-1 cephalosporinase in Escherichia coli

Three Escherichia coli isolates resistant to third-generation cephalosporins but negative for extended-spectrum β-lactamase production were isolated from hospitalised patients in Zagreb, Croatia, during June 2003 to February 2004. Resistance was due to the inducible production of a DHA-1 cephalosporinase. Each isolate contained an integron-associated blaDHA-1–ampR sequence carried by similar-sized plasmids, of which one was self-transferable. Serotyping and polymerase chain reaction typing using ERIC2 primer indicated that the isolates were distinct. This is the first description of DHA β-lactamase production in E. coli.