임상검체에서 분리된 Enterobacteriaceae 균종의 extended-spectrum β-lactamase 유형 및 분자유전학적 특성

Abstract

Background No significant information on the prevalence of extended-spectrum -lactamase (ESBL)-producing Enterobacteriaceae in Korea has been available, because a few studies conducted to date in Korea have involved only discontinuous isolates of Klebsiella pneumoniae and Escherichia coli. In this study, a survey of clinical isolates of Enterobacteriaceae was carried out to assess the prevalence of ESBL-producing Enterobacteriaceae and to investigate the ESBL derivatives for phenotypical and genotypical characteristics. Methods A total of 500 consecutive clinical isolates of Enterobacteriaceae were screened for the presence of ESBL according to the new guidelines of the National Committee for Clinical Laboratory Standards. A double-disk synergy test, as a confirmatory test, was performed in screening positive strains. The presence of the ESBL gene was determined using polymerase chain reaction (PCR). The types of the -lactamase gene were determined by isoelectric focusing and nucleotide sequence analysis. Results Among the collected strains, 21 of 293 E. coli (7.2%), 46 of 108 K. pneumoniae (42.6%), 10 of 20 Enterobacter cloacae (50.0%), 1 of 12 E. aerogenes (8.3%), 12 of 16 Citrobacter freundii (75.5%), and 1 of 14 Serratia marcescens (7.2%) were ESBL-producing strains. DNA sequencing and deduced amino acid sequence analysis revealed TEM-52 specific mutations in five strains (1 E. coli, 3 K. pneumoniae, and 1 E. cloacae) expressing pI 6.0 -lactamases, SHV-2a in two K. pneumoniae of pI 7.6, and SHV-12 in four strains (1 E. coli of pI 8.2, 1 K. pneumoniae of pI 7.8, and 2 K. pneumoniae of pI 8.4). Conclusion ESBLs were present in other genera of the family Enterobacteriaceae, such as Enterobacter, Citrobacter, and Serratia in Korea. ESBL types in E. coli isolates were TEM-52, SHV-12, and SHV-2a in decreasing order, and in K. pneumoniae isolates were TEM-52, SHV-2a and SHV-12 in decreasing order. The pIs of SHV-12 were 8.4 and 7.8 as well as 8.2, and a TEM-52 producing E. cloacae was first found.