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Availability of MADLDI-TOF MS for Identification of Gram Positive Bacilli Isolated from Blood Culture
Biomed Sci Letters 2018;24:108-115
Published online June 30, 2018;  https://doi.org/10.15616/BSL.2018.24.2.108
© 2018 The Korean Society For Biomedical Laboratory Sciences.

Jin-Un Choi1,짠, Sang-Ha Kim2,짠, Su-Jeong Hwang3, Young-Bin Yu5, Sunghyun Kim4, and Young-Kwon Kim5,

1Department of Laboratory Medicine, Chonnam National University Hospital, Gwangju 61469, Korea
2Department of Laboratory Medicine, Konyang University Hospital, Daejeon 35365, Korea
3Department of Dental Hygiene, College of Medical Sciences, Konyang University, Daejeon 35365, Korea
4Department of Clinical Laboratory Science, College of Health Sciences, Catholic University of Pusan, Busan 46252, Korea
5Department of Biomedical Laboratory Science, College of Medical Sciences, Konyang University, Daejeon 35365, Korea
Correspondence to: Sunghyun Kim. Department of Clinical Laboratory Science, College of Health Sciences, Catholic University of Pusan, Busan 46252, Korea.
Tel: +82-51-510-0560, Fax: +82-51-510-0568, e-mail: shkim0423@cup.ac.kr
Young-Kwon Kim. Department of Biomedical Laboratory Science, College of Medical Sciences, Konyang University, Daejeon 35365, Korea.
Tel: +82-42-660-6371, Fax: +82-42-543-6370, e-mail: ykkim3245@konyang.ac.kr
Jin-Un Choi and Sang-Ha Kim contributed equally to this article.
Received March 5, 2018; Revised April 25, 2018; Accepted May 17, 2018.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
 Abstract
In the present study, results of the identification of Gram-positive bacilli (GPB) were analyzed by using the MALDI-TOF MS technique to score each 2-year blood culture at a university hospital. In addition, 16S rRNA sequence analyses and MALDI-TOF MS results are compared to targeting strains that had been isolated two or more times within the same patient, to evaluate the usefulness of MALDI-TOF MS in GPB identification. According to the cut-off (돟 1.7) criteria, there were 410 (57.5%) reliable strains and 303 (42.5%) non-identified strains among the GPB identification results of 713 strains, using a microflex MALDI Biotyper (Bruker Daltonik GmbH, Bremen, Germany). The isolation appeared most often in the following order: Corynebacterium striatum, Bacillus cereus, Bacillus subtilis, Paenibacillus urinalis, and Listeria monocytogenes. Nearly three-fourths, 66 out of 89 (74.2%) of the strains for Corynebacterium striatum; 44 out of 60 (73.3%) strains for Bacillus cereus; and all (25 out of 25, 100%) Listeria monocytogenes strains were identified by their high scores of 2.0 or higher. Most (293 strains out of 303) non-identified strains were strains isolated only once and not significant as infectious bacilli. A total of 43 out of 50 (86.0%) strains matched and were able to be identified based on the 16 rRNA sequencing comparison results of strains that were isolated twice or more within the same patient and significant as infection bacilli. Non-matching among 5 out of 7 strains was not identified, even with MALDI-TOF MS. In conclusion, GPB can be identified in blood cultures using MALDI-TOF MS. This can be done accurately with ease, rapidly, and at a low cost. It is also thought to be helpful in GPB diagnosis and treatment.
Keywords : Blood culture, Gram positive bacilli, MADLDI-TOF MS, 16S rRNA sequencing