ABSTRACT
BACKGROUND: The aim of this study was to determine a nation-wide prevalence of Ambler class A and D extended-spectrum-lactamases (ESBL) in Klebsiella pneumoniae isolates in Korea. METHODS: During the period of April to May 2005, 189 isolates of K.pneumoniae were collected from 11 Korean hospitals. Antimicrobial susceptibilities to ceftazidime and cefotaxime were tested by the disk diffusion method, and ESBL production was determined by double-disk synergy test. Determinants of ceftazidime or cefotaxime-resistance were transferred to Escherichia coli J53 (azide-resistant) by transconjugation. Genotypes of class A and D ESBL genes were determined by PCR amplification and sequencing. RESULTS: One hundred-sixty isolates of K.pneumoniae showed positive results in double-disk synergy test. The most prevalent ESBL was SHV-12 (n=148). Also detected were genes encoding ESBLs including TEM-52 (n=1), SHV-2a (n=2), CTX-M-3 (n=15), CTX-M-9 (n=6), CTX-M-12 (n=2), CTX-M-14 (n=9), CTX-M-15 (n=1), PER-1 (n=1), GES-5 (n=3), and OXA-30 (n=2) beta-lactamases. CONCLUSION: With the emergence of CTX-M-12, PER-1, and OXA-30 beta-lactamases, the ESBLs in K.pneumoniae isolates are becoming more diverse in Korea.