Survey of Klebsiella pneumoniae strains producing extended-spectrum beta-lactamases: prevalence of SHV-12 and SHV-2a in Korea.

Fifty-three clinical isolates of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae collected from three hospitals in Korea were investigated for phenotypical and genotypical characterizations. Among these, 39 strains (74%) were shown by isoelectric focusing to carry SHV-type beta-lactamases: 27 strains showed the pI 8.2 beta-lactamase, and another 12 strains showed the pI 7.6 beta-lactamase. The SHV gene of each of these strains was amplified by PCR, followed by nucleotide sequencing analysis. The gene of the pI 8.2 beta-lactamase was found to be identical to the sequences encoding SHV-12, and the gene of the pI 7.6 beta-lactamase was identical to the sequences encoding SHV-2a. A total of eight cefoxitin-resistant strains were found to have the plasmid-mediated AmpC-type beta-lactamase, with a pI of 8.0, and this was confirmed to be CMY-1 beta-lactamase by PCR and hybridization analysis. Noteworthy in this study is the fact that SHV-12 and SHV-2a have been the most commonly identified SHV-type ESBLs in Korea.