염색체성 AmpC β-lactamase 생성 Enterobacteriaceae 균종에서의 CTX-M형 extended-spectrum β-lactamase 검출과 분자유전학적 특성 규명
Other Titles
Detection of CTX-M-Type Extended-Spectrum β-Lactamase in Clinical Isolates of Chromosomal AmpC β-Lactamase-Producing Enterobacteriaceae from Korea and Their Molecular Characteristics
Authors
김창기 ; 염종화 ; 용동은 ; 정석훈 ; 이경원 ; 정윤섭
Citation
Korean Journal of Clinical Microbiology (대한임상미생물학회지), Vol.11(2) : 90-97, 2008
Background: Clinical isolates of AmpC β-lactamase producing Enterobacteriaceae were evaluated to determine the prevalence of CTX-M extended-spectrum β-lactamases (ESBLs) and their genetic environments.
Methods: A total of 250 non-duplicate isolates of Eneterobacter aerogenes, E. cloacae, Citrobacter freundii, Serratia marcescens and Morganella morganii were collected at a Korean hospital. ESBL production was determined by double disk synergy test. For ESBL producers, bla genes were sequenced and
blaCTX-M environment was characterized by PCR mapping and sequencing.
Results: Among the 250 isolates 29 (11.6%) produced ESBL, and 14 of the 29 isolates produced CTX-M ESBLs, including CTX-M-9 by 8 isolates, CTX-M-3 by 4 isolates, CTX-M-12 by 1 isolate, and CTX-M-14 by 1 isolate. ISEcp1 was present upstream of blaCTX-M-3, 12, and 14. Three of the four CTXM-3 producers had the same genetic environment (pemK-ISEcp1-blaCTX-M-3-orf477-mucA). An IS903-like element was found downstream of blaCTX-M-14. ISCR1 was identified upstream of blaCTX-M-9 and ISCR1 and blaCTX-M-9 were located on sul1-type class 1 integron. The variable region between the 5’-CS and the first 3’-CS contained dfrA16 and aadA2. Its structure was similar to that of In60, but our isolates did not have IS3000 or second 3’-CS.
Conclusion: CXT-M type ESBL was prevalent in AmpC β-lactamase-producing Enterobacteriaceae, particularly E. cloacae. blaCTX-M genes were associated with ISEcp1 or ISCR1. This is the first report on the genetic environment of blaCTX-M in Korean isolates.