Survey of Klebsiella pneumoniae Strains Producing Extended-Spectrum β-Lactamases: Prevalence of SHV-12 and SHV-2a in Korea

Fifty-three clinical isolates of extended-spectrum β-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 β-lactamases: 27 strains showed the pI 8.2 β-lactamase, and another 12 strains showed the pI 7.6 β-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 β-lactamase was found to be identical to the sequences encoding SHV-12, and the gene of the pI 7.6 β-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 β-lactamase, with a pI of 8.0, and this was confirmed to be CMY-1 β-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.