Detection of SHV-5 extended-spectrum beta-lactamase in Klebsiella pneumoniae strains isolated in Italy.

Thirty-five Klebsiella pneumoniae strains isolated during 1993-1994 in intensive care units of a large Italian hospital were examined for the presence of extended-spectrum beta-lactamases. Five strains showed a high level of simultaneous resistance to beta-lactam agents, including ceftazidime and aztreonam, conferred by a large (130 kb) self-transferable plasmid (in 4 of 5 strains). Isoelectrofocusing and hybridisation studies suggest that these enzymes can be identified as SHV-5 extended-spectrum beta-lactamases. Pulsed-field get electrophoresis analysis showed three different genomic fingerprinting profiles, while plasmid restriction enzyme digestion revealed three different patterns, demonstrating that the diffusion of SHV-5 beta-lactamase is not the result of a single strain or plasmid dissemination.