Annals of Laboratory Medicine

Korean Society for Laboratory Medicine (대한진단검사의학회)
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Usefulness of a Chromogenic Selective Agar for the Identification of Bacillus cereus Isolated from Blood Cultures

  • Jeong, Eun-Sun (Department of Laboratory Medicine, Chonnam National University Medical School) ;
  • Shin, Jong-Hee (Department of Laboratory Medicine, Chonnam National University Medical School) ;
  • Shin, Myung-Geun (Department of Laboratory Medicine, Chonnam National University Medical School) ;
  • Suh, Soon-Pal (Department of Laboratory Medicine, Chonnam National University Medical School) ;
  • Ryang, Dong-Wook (Department of Laboratory Medicine, Chonnam National University Medical School)
  • Received : 2010.03.15
  • Accepted : 2010.07.22
  • Published : 2010.08.31
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Abstract

Background : The incidence of Bacillus cereus bacteremia is increasing, but the identification of Bacillus species remains difficult. Brilliance Bacillus cereus agar (BBC agar; Oxoid, UK) is a new CHROMagar medium that allows selective isolation and identification of B. cereus; however, its clinical usefulness is seldom studied. We evaluated the usefulness of BBC agar to identify B. cereus isolates recovered from blood cultures. Methods : We analyzed a total of 53 blood isolates that showed a Bacillus-like morphology on Gram staining. All isolates were identified by using both the API Coryne (bioM$\acute{e}$rieux, France) and API 50CH/B (bioM$\acute{e}$rieux) systems. They were subsequently subcultured on BBC agar, incubated for 24 hr, and then examined for characteristic blue-green colonies. The clinical characteristics of patients whose isolates were identified as B. cereus were assessed. Results : Of the 53 isolates, 18 were identified as B. cereus by API 50CH/B. With the API 50CH/B system used as gold standard, the sensitivity and specificity for the identification of B. cereus were 100% (18/18) and 100% (35/35), respectively, using BBC agar, and 67% (12/18) and 100% (35/35), respectively, using the API Coryne system. Of the 18 patients with B. cereus bacteremia, 15 showed infectious signs, and 3 had more than 2 blood cultures positive for B. cereus on separate days. Conclusions : Our study shows, for the first time, that BBC agar, with its good agreement and ease of use, is a valuable alternative to the API 50CH/B system for the presumptive identification of B. cereus isolates from blood cultures.

배경 : 최근 Bacillus cereus에 의한 균혈증의 빈도가 증가되고 있으나, Bacillus 균종을 동정하는 것은 쉽지 않다. Brilliance Bacillus cereus agar (BBC 발색배지, Oxoid, UK)는 B. cereus를 선택적으로 분리하고 동정하기 위한 발색배지로 비교적 최근에 소개되었는데 임상 균주를 대상으로 한 평가는 접하기 어렵다. 본 연구에서는 혈액배양에서 분리된 B. cereus를 동정하는 데 있어 BBC 발색배지의 유용성을 조사해보았다. 방법 : 혈액배양에서 분리된 그람양성 막대균 중 Bacillus 모양을 보이는 53주를 대상으로 하였다. 대상 균주는 API Coryne system (bioM$\acute{e}$rieux, France) 및 API 50CH/B system (bioM$\acute{e}$rieux)으로 동정하였고, 동시에 BBC 발색배지에 접종하여 24시간 후 성장 및 발색 여부를 확인하였다. 혈액에서 B. cereus가 분리된 환자에 대해서는 임상적 특성을 조사하였다. 결과 : API 50CH/B system으로 53주 중 18주가 B. cereus로 동정되었고, API 50CH/B system 결과를 기준으로 할 때 API Coryne system을 이용한 동정의 민감도와 특이도는 각각 67% (12/18) 및 100% (35/35)인 반면, BBC 발색배지를 이용한 동정의 민감도와 특이도는 둘 다 100%이었다. 18명의 B. cereus 균혈증이 있었던 환자 중 15명이 감염의 징후를 보였고, 3명은 혈액배양에서 두 번 이상 균이 분리되었다. 결론 : 본 연구결과, 혈액배양에서 분리된 B. cereus의 동정에 있어 BBC 발색배지는 API 50CH/B system과 100%의 일치율을 보여 API 50CHB를 대신하여 혈액분리 B. cereus 균을 간편 동정하는데 이용될 수 있으리라 생각된다.

Keywords

Acknowledgement

Supported by : Chonnam National University Hospital Research Institute of Clinical Medicine

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