Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

Evaluation of Combined Use of BacT/ALERT 3D Liquid Culture System and PCR-RFLP for Detection and Identification of Mycobacteria from Bronchial Specimens

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2009 March, Volume 12, Issue 1, pages 37-42.

https://doi.org/10.5145/ACM.2009.12.1.37

Evaluation of Combined Use of BacT/ALERT 3D Liquid Culture System and PCR-RFLP for Detection and Identification of Mycobacteria from Bronchial Specimens

Hae-Sun Chung, Chang-Seok Ki, Jang Ho Lee, Nam Yong Lee

Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea

Abstract

Background: We evaluated BacT/ALERT 3D liquid culture system (bioMerieux, USA) and PCR-restriction fragment length polymorphism (RFLP) for recovery and direct identification of mycobacteria, and the results were compared with a conventional culture system using an egg-based solid medium. 

Methods: A total of 3,037 bronchial specimens (2,309 bronchial washing fluids and 728 bronchoalveolar lavages) were collected. Decontaminated specimens were inoculated to both BacT/ALERT MP liquid media and Ogawa solid media (3%, Shinyang, Korea). Recovery rate and detection time were compared between the two systems. Liquid media from positive cultures were centrifuged and the pellets were tested for direct identification of mycobacteria by PCR-RFLP using Myco-ID (M&D Inc., Korea). 

Results: A total of 518 isolates, including 215 M. tuberculosis (MTB) and 303 non-tuberculosis mycobacteria (NTM), were recovered. The liquid media detected 492 isolates (16.2%), including 195 MTB and 297 NTM), whereas the solid media detected 416 isolates (13.7%), including 187 MTB and 229 NTM (P<0.001); 102 isolates (28 MTB and 74 NTM) were recovered only by the liquid media, while 26 (20 MTB and 6 NTM) isolates were recovered only by the solid media. The mean time to detection was 18.1 days by the liquid media and 29.3 days by the solid media (P<0.001). The overall time to species identification from inoculation was 21.8 days. Direct PCR-RFLP from the liquid media identified 39.1% of MTB, 6.3% of M. avium, 19.05 of M. abscessus, and 12.6% of M. intracellulare respectively. 

Conclusion: Combined use of a liquid culture system and PCR-RFLP improved the recovery rate and shortened the detection time. However, solid media is still necessary to maximize the diagnostic efficiency. (Korean J Clin Microbiol 2009;12:37-42)

Keywords

Mycobacteria, Culture, Liquid media, PCR- RFLP, Bronchial specimen