Ann Lab Med 2018; 38(3): 235-241
Same-Day Identification and Antimicrobial Susceptibility Testing of Bacteria in Positive Blood Culture Broths Using Short-Term Incubation on Solid Medium with the MicroFlex LT, Vitek-MS, and Vitek2 Systems
Jihye Ha, M.D.1, Sung Kuk Hong, M.D.2, Geum Hee Han, M.T.1, Myungsook Kim, M.T.1, Dongeun Yong, M.D.1, and Kyungwon Lee, M.D.1
Department of Laboratory Medicine1 and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul; Department of Laboratory Medicine2, National Cancer Center, Goyang, Korea
Corresponding author: Dongeun Yong
Department of Laboratory Medicine, Yonsei University College of Medicine, 50 Yonseiro, Seodaemun-gu, Seoul 03722, Korea
Tel: +82-2-2228-2442
Fax: +82-2-364-1583
Co-corresponding author: Sung Kuk Hong
Department of Laboratory Medicine, National Cancer Center, Goyang, 323 Ilsanro, Ilsandong-gu, Goyang 10408, Korea
Tel: +82-31-920-1324
Fax: +82-2-364-1583
Received: March 24, 2017; Revised: August 16, 2017; Accepted: December 14, 2017; Published online: May 1, 2018.
© Korean Society for Laboratory Medicine. All rights reserved.

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Background: Early and appropriate antibiotic treatment improves the clinical outcome of patients with septicemia; therefore, reducing the turn-around time for identification (ID) and antimicrobial susceptibility test (AST) results is essential. We established a method for rapid ID and AST using short-term incubation of positive blood culture broth samples on solid media, and evaluated its performance relative to that of the conventional method using two rapid ID systems and a rapid AST method.
Methods: A total of 254 mono-microbial samples were included. Positive blood culture samples were incubated on blood agar plates for six hours and identified by the MicroFlex LT (Bruker Daltonics) and Vitek-MS (bioMeriéux) systems, followed by AST using the Vitek2 System (bioMeriéux).
Results: The correct species-level ID rates were 82.3% (209/254) and 78.3% (199/254) for the MicroFlex LT and Vitek-MS platforms, respectively. For the 1,174 microorganism/antimicrobial agent combinations tested, the rapid AST method showed total concordance of 97.8% (1,148/1,174) with the conventional method, with a very major error rate of 0.5%, major error rate of 0.7%, and minor error rate of 1.0%.
Conclusions: Routine implementation of this short-term incubation method could provide ID results on the day of blood culture-positivity detection and one day earlier than the conventional AST method. This simple method will be very useful for rapid ID and AST of bacteria from positive blood culture bottles in routine clinical practice.
Keywords: Antimicrobial susceptibility testing, Rapid identification, Septicemia, MALDITOF-MS, Blood culture

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