Korean Journal of Clinical Laboratory Science (대한임상검사과학회지)

Korean Society for Clinical Laboratory Science (대한임상검사과학회)
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Characterization of bft Genes among Enterotoxigenic Bacteroides fragilis Isolates from Extraintestinal Specimens at a University Hospital in Korea

국내 한 대학병원의 임상검체에서 분리된 Bacteroides fragilis 독소 유전자의 특성

  • Kim, Myungsook (Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Severance Hospital, Yonsei University College of Medicine) ;
  • Kim, Hyunsoo (Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Severance Hospital, Yonsei University College of Medicine) ;
  • Ji, Seung Eun (Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Severance Hospital, Yonsei University College of Medicine) ;
  • Rim, John Hoon (Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Severance Hospital, Yonsei University College of Medicine) ;
  • Gwon, Sun Yeong (Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University at Wonju) ;
  • Kim, Wan Hee (KOTITI Testing and Research Institute) ;
  • Rhee, Ki-Jong (Department of Biomedical Laboratory Science, College of Health Sciences, Yonsei University at Wonju) ;
  • Lee, Kyungwon (Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Severance Hospital, Yonsei University College of Medicine)
  • 김명숙 (연세대학교 세브란스병원 진단검사의학과 및 세균내성연구소) ;
  • 김현수 (연세대학교 세브란스병원 진단검사의학과 및 세균내성연구소) ;
  • 지승은 (연세대학교 세브란스병원 진단검사의학과 및 세균내성연구소) ;
  • 임정훈 (연세대학교 세브란스병원 진단검사의학과 및 세균내성연구소) ;
  • 권선영 (연세대학교 보건과학대학 임상병리학과) ;
  • 김완희 (KOTITI 시험연구원) ;
  • 이기종 (연세대학교 보건과학대학 임상병리학과) ;
  • 이경원 (연세대학교 세브란스병원 진단검사의학과 및 세균내성연구소)
  • Received : 2016.04.16
  • Accepted : 2016.05.26
  • Published : 2016.06.30
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Abstract

Enterotoxigenic Bacteroides fragilis (ETBF) produces enterotoxins known to be a virulence factor. Three isotypes of the B. fragilis toxin (BFT) gene have been identified: bft-1, bft-2, and bft-3. We investigated the presence of bft isotypes in clinical B. fragilis isolates and the antimicrobial resistance of BFT-negative and BFT-positive isolates. Overall, 537 B. fragilis isolates were collected from extraintestinal specimens over 8 years (2006~2013) from a university hospital in Korea. Samples were analyzed by multiplex PCR to identify the bft gene isotypes. Additionally, the antimicrobial susceptibility of 107 B. fragilis isolates (74 BFT-negative and 33 BFT-positive) was examined by the CLSI agar dilution method. PCR revealed a total bft gene detection rate of 30%, while 33% and 29% of blood and other extraintestinal isolates contained the gene, respectively. Among ETBF isolates, the most common isotype was bft-1 gene, followed by bft-2 and bft-3 (bft-1 77%, bft-2 14%, bft-3 9%). Resistance rates (%) for BFT-negative and positive isolates differed in response to various antimicrobial agents, with 3%, 5%, 1% and 38% of BFT-negative isolates and 3%, 6%, 3% an 42% of BFT-positive isolates being resistant to piperacillin-tazobactam, cefoxitin, imipenem, and clindamycin, respectively. Interestingly, neither BFT-negative nor positive isolates showed antimicrobial resistance to chloramphenicol and metronidazole. Overall, the proportion of ETBF from blood was similar to that of other extraintestinal sites and the bft-1 gene was the predominant isotype. Higher antimicrobial resistance rates were found in BFT-positive isolates than BFT-negative isolates, but these differences were not statistically significant.

Enterotoxigenic Bacteroides fragilis (ETBF)는 병독소 인자로 알려진 장독소를 생성하는 균종이다. B. fragilis enterotoxin (BFT)은 bft-1, bft-2 및 bft-3 세 개의 유전자 아형들이 밝혀졌다. 본 연구에서는 임상 검체에서 분리된 B. fragilis에서 bft 유전자의 유무와 BFT 음성 및 양성 균주의 항균제 내성을 조사하였다. 국내의 한 대학병원에서 8년간(2006~2013년) 장외 검체에서 분리된 B. fragilis는 총 537주이었다. 다중중합연쇄반응으로 시험하여 bft 유전자 아형을 확인하였다. BFT 음성 74주와 양성 33주를 포함한 B. fragilis 107주의 항균제 감수성은 CLSI 한천희석법으로 시험하였다. 임상 검체에서 분리된 B. fragilis의 bft 유전자 검출율은 30% 이었고, 이 중 혈액과 혈액 외 장외 검체 분리주에서는 각각 33%, 29% 이었다. ETBF 중에서 가장 흔한 아형은 bft-1 이었고, 그 다음은 bft-2, bft-3 순이었다(bft-1: 77%, bft-2: 14%, bft-3: 9%). BFT-음성과 양성 균주의 내성률은 일부 항균제에 대해서 차이가 있었다(BFT-음성 균주: piperacillin-tazobactam 3%, cefoxitin 5%, imipenem 1%, clindamycin 38%; BFT-양성 균주: piperacillin-tazobactam 3%, cefoxitin 6%, imipenem 3%, clindamycin 42%). BFT-음성 및 BFT-양성 균주 모두는 chloramphenicol과 metronidazole에 대한 내성은 없었다. 결론적으로, 혈액 분리주에서의 ETBF 검출율은 혈액 외 장외 검체 분리주에서와 비슷하였고, 가장 흔한 유전자 아형은 bft-1 이었다. 항균제 내성은 BFT 양성 균주가 음성 균주보다 대체로 높았으나 통계학적으로 유의한 차이는 없었다.

Keywords

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