배경：부산의 한 대학병원에서 분리된 Enterobacter cloacae를 대상으로 Ambler class A extendedspectrum β-lactamase (ESBL)의 종합적인 생성 현황을 조사하고 이들 효소를 생성하는 균주의 감염역학을 조사하고자 하였다. 방법：2003년에 고신대학교 복음병원 환자에서 분리된 E. cloacae를 대상으로 항균제에 대한 감수성을 디스크확산법으로 시험하였으며, ESBL 생성은 double disk synergy (DDS) 시험으로 조사하였다. ESBL 생성 균주의 cefotaxime 내성 전달성을 접합으로 시험하였다. β-lactam 항균제의 최소억제농도를 한천희석법으로 측정하였으며, TEM형, SHV형, CTX-M형, PER-1형, VEB형, IBC형, GES형 및 TLA형 유전자를 polymerase chain reaction (PCR)으로 검출하였고 PCR 산물의 염기서열을 양방향으로 분석하였다. β-lactamase의 pI값을 Isoelectric focusing으로 측정하였다. CTX-M-9 유전자를 지닌 균주를 대상으로 enterobacterial repetitive intergenic consensus (ERIC) PCR로 유전형을 분류하고 균주의 역학적 연관성을 조사하였다. 결과：시험기간 중 분리된 E. cloacae 148주의 ceftazidime, cefotaxime 및 aztreonam에 대한 내성율은 각각 50.0%, 29.6% 및 48.0%이었으며, 광범위 β-lactam 항균제 하나 이상에 중간 혹은 내성인 50주 중 41주(27.7%)가 DDS 양성이었다. 대상 균주 중 1주(2%)는 blaTEM-52, 16주(32%)는 blaSHV-12, 4주(8%)는 blaCTX-M-9 유전자만을 지니고 있었으며, 19주(38%)는 blaSHV-12 와 blaCTX-M-9 유전자를 동시에 지니고 있었다. blaCTX-M-9 유전자를 지닌 균주(23주)는 ERIC PCR에 의하여 9가지 형으로 분류되었다. 결론：부산의 한 대학병원에서 분리되는 E. cloacae는 ESBL을 흔히 생성하며, SHV-12와 CTX-M-9이 가장 흔한 ESBL임을 확인할 수 있었다. CTX-M-9 생성 E. cloacae는 ERIC PCR에 의하여 다양한 유전형으로 분류되어 동일 감염원에서 유래되지 않았음을 확인할 수 있었다.

Background: The aim of this study is to assess the prevalence and to investigate the molecular epidemiology of Ambler class A extended-spectrum β-lactamase (ESBL)-producing Enterobacter cloacaeisolates in a university hospital in Busan, Korea. Methods: Non-duplicated clinical isolates of E. cloacae from patients admitted in Kosin University Gospel Hospital were collected during the period from January through September, 2003. ESBL-production was examined by the double-disk synergy test (DDST) and the transferability of cefotaxime-resistance by conjugation. MICs of β-lactam antibiotics were determined by the agar dilution method and Ambler class A ESBL genes were searched by PCR amplification. Enterobacterial repetitive intergenic consensus (ERIC) PCR was performed to investigate epidemiological relationships among blaCTX-M-9 gene-carrying E. cloacaeisolates. Results: Antimicrobial resistance rates of E. cloacae isolates (n=148) to ceftazidime, cefotaxime, and aztreonam were 50.0%, 29.6%, and 48.0%, respectively. Among 50 E. cloacae isolates intermediate or resistant to more than one expanded-spectrum β-lactam agent, 41 (27.7%) showed positive results in DDST; of these 41 isolates, 1 was found to carry blaTEM-52 gene, 16 carried blaSHV-12 gene, 4 blaCTX-M-9 gene, and 19 both blaSHV-12 and blaCTX-M-9 genes. The 23 E. cloacae isolates carrying blaCTX-M-9 gene showed 9 different profiles by ERIC PCR. Conclusion: ESBL-producing E. cloacae was not uncommon in a university hospital in Busan, Korea. The commonest types of ESBLs produced by E. cloacaeisolates were SHV-12 and CTX-M-9. CTX-M-9 ESBL-producing E. cloacaeisolates showed diverse ERIC-PCR profiles, indicating that they were not originated from a common source.

Background: The aim of this study is to assess the prevalence and to investigate the molecular epidemiology of Ambler class A extended-spectrum β-lactamase (ESBL)-producing Enterobacter cloacaeisolates in a university hospital in Busan, Korea. Methods: Non-duplicated clinical isolates of E. cloacae from patients admitted in Kosin University Gospel Hospital were collected during the period from January through September, 2003. ESBL-production was examined by the double-disk synergy test (DDST) and the transferability of cefotaxime-resistance by conjugation. MICs of β-lactam antibiotics were determined by the agar dilution method and Ambler class A ESBL genes were searched by PCR amplification. Enterobacterial repetitive intergenic consensus (ERIC) PCR was performed to investigate epidemiological relationships among blaCTX-M-9 gene-carrying E. cloacaeisolates. Results: Antimicrobial resistance rates of E. cloacae isolates (n=148) to ceftazidime, cefotaxime, and aztreonam were 50.0%, 29.6%, and 48.0%, respectively. Among 50 E. cloacae isolates intermediate or resistant to more than one expanded-spectrum β-lactam agent, 41 (27.7%) showed positive results in DDST; of these 41 isolates, 1 was found to carry blaTEM-52 gene, 16 carried blaSHV-12 gene, 4 blaCTX-M-9 gene, and 19 both blaSHV-12 and blaCTX-M-9 genes. The 23 E. cloacae isolates carrying blaCTX-M-9 gene showed 9 different profiles by ERIC PCR. Conclusion: ESBL-producing E. cloacae was not uncommon in a university hospital in Busan, Korea. The commonest types of ESBLs produced by E. cloacaeisolates were SHV-12 and CTX-M-9. CTX-M-9 ESBL-producing E. cloacaeisolates showed diverse ERIC-PCR profiles, indicating that they were not originated from a common source.

Enterobacter cloacae, SHV-12, CTX-M-9, Enterobacterial repetitive intergenic consensus, Polymerase chain reaction