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 (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)

서지정보

· 발행기관 : 대한임상미생물학회
· 수록지 정보 : Annals of Clinical Microbiology / 11권 / 2호 / 90 ~ 97페이지
· 저자명 : 김창기, 염종화, 용동은, 정석훈, 이경원, 정윤섭

초록

배경: 세계 여러 지역에서 CTX-M형 extended-spectrum β-lactamase (ESBL)를 생성하는 그람음성 간균이 증가하고 있다.
본 연구에서는 AmpC β-lactamase 생성 Enterobacteriaceae 균종에서 CTX-M형 ESBL유전자를 검출하고, blaCTX-M의 주변
유전구조를 규명하고자 하였다.
방법: 2006년 4월부터 9월까지 국내 1개 대학병원에서 분리된 Enterobacter cloacae, E. aerogenes, Citrobacter freundii,
Serratia marcescens, Morganella morganii의 일련 균주를 50주씩 수집하였다. ESBL생성은 ceftazidime, cefotaxime, cefepime
및 amoxicillin-clavulanic acid 디스크를 이용한 double disk synergy로 시험하였다. ESBL 유전자형 규명을 위해 blaTEM,
blaSHV, blaCTX-M, blaGES 및 blaVEB 유전자를 PCR로 증폭한 후 염기서열을 분석하였다. CTX-M이 양성인 경우 IS element와
integron 등의 주변 구조를 분석하였고 염색체를 XbaI으로 처리해 pulsed-field gel electrophoresis를 시행하였다.
결과: 시험된 250주 중 ESBL 생성주는 E. cloacae 10주, S. marsescens 8주, E. aerogenes 6주, C. freundii 4주, M. morganii
1주의 29주(12%)이었다. SHV-12와 CTX-M-9 유전자를 동시에 가진 균주가 6주, SHV-12가 9주, SHV-2a가 1주, TEM-52가
5주, CTX-M-3가 4주, CTX-M-9가 2, CTX-M-14와 CTX-M-12가 각각 1주이었다. 모든 blaCTX-M-9는 ISCR1을 포함하는 class
1 sul1-type integron에 있었으며, blaCTX-M-3, blaCTX-M-12 및 blaCTX-M-14 유전자의 상류에는 ISEcp1이 있었다. CTX-M-3 양성주
중 3주는 pemK-ISEcp1-blaCTX-M-3-mucA의 유전자 구조를 갖고 있었다.
결론: 염색체성 AmpC β-lactamase 생성 Enterobacteriaceae 중에 ESBL 생성균주가 흔하였으며 가장 흔한 ESBL형은
SHV-12이었고, 그 다음은 CTX-M-9이었다. CTX-M유전자는 ISEcp1와 연관되거나 complex integron에 존재하였다.

영어초록

Background: Clinical isolates of AmpC β-lactamaseproducing
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.

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