Direct Identification and Antimicrobial Susceptibility Testing of Bacteria From Positive Blood Culture Bottles by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and the Vitek 2 System.
10.3343/alm.2016.36.2.117
- Author:
Sung Jin JO
1
;
Kang Gyun PARK
;
Kyungja HAN
;
Dong Jin PARK
;
Yeon Joon PARK
Author Information
1. Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea. yjpk@catholic.ac.kr
- Publication Type:Original Article ; Research Support, Non-U.S. Gov't
- Keywords:
Direct identification;
MALDI-TOF MS;
Vitek MS;
Vitek 2;
Positive blood culture
- MeSH:
Adult;
Ammonium Chloride/chemistry;
Anti-Infective Agents/*pharmacology;
Child;
Gram-Negative Bacteria/drug effects/*isolation & purification/metabolism;
Gram-Positive Bacteria/drug effects/*isolation & purification/metabolism;
Humans;
Reagent Kits, Diagnostic;
Saponins/chemistry;
*Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
- From:Annals of Laboratory Medicine
2016;36(2):117-123
- CountryRepublic of Korea
- Language:English
-
Abstract:
BACKGROUND: We evaluated the reliability and accuracy of the combined use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) bacterial identification and Vitek 2 antimicrobial susceptibility testing (AST) for bacteria from positive blood culture bottles. METHODS: Direct identification and AST were performed in parallel to the standard methods in monomicrobial positive blood culture bottles. In total, 254 isolates grown on aerobic and/or anaerobic bottles were identified with MALDI-TOF Vitek MS (bioMerieux, France), and 1,978 microorganism/antimicrobial agent combinations were assessed. For isolates from anaerobic bottles, an aliquot of the culture broth was centrifuged, washed, and filtered through a nylon mesh. For isolates from aerobic/pediatric bottles, a lysis step using 9.26% ammonium chloride solution and 2% saponin solution was included. RESULTS: The overall correct identification rate was 81.8% (208/254) and that for gram-positive/gram-negative isolates was 73.9%/92.6%, respectively, and it was 81.8%, 87.6%, and 57.9% for isolates from aerobic, anaerobic, and pediatric bottles, respectively. Identification was not possible in 45 cases, and most of these isolates were streptococci (N=14) and coagulase-negative staphylococci (N=11). Misidentification occurred only in one case. Compared with standard methods, direct AST showed 97.9% (1,936/1,978) agreement with very major error of 0.25%, major error of 0.05%, and minor error of 1.8%. CONCLUSIONS: This simple and cost-effective sample preparation method gives reliable results for the direct identification and AST of bacteria. For the identification of streptococci and coagulase-negative staphylococci, the method should be further improved.
