Ann Lab Med.  2015 Jan;35(1):62-68. 10.3343/alm.2015.35.1.62.

Evaluation of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry-Based VITEK MS System for the Identification of Acinetobacter Species from Blood Cultures: Comparison with VITEK 2 and MicroScan Systems

• Lee SY
• Shin JH
• Kim SH
• Shin MG
• Suh SP
• Ryang DW

• KMID: 2363149
• DOI: http://doi.org/10.3343/alm.2015.35.1.62

Abstract

BACKGROUND
Acinetobacter species are the leading cause of bloodstream infection (BSI), but their correct identification is challenging. We evaluated the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)-based VITEK MS (bioMerieux, France), and two automated systems, VITEK 2 (bioMerieux) and MicroScan (Siemens, USA) for identification of Acinetobacter BSI isolates.
METHODS
A total of 187 BSI isolates recovered at a university hospital in Korea between 2010 and 2012 were analyzed. The identification results obtained using VITEK MS and two automated systems were compared with those of rpoB sequencing.
RESULTS
Of 187 isolates analyzed, 176 were identified to the species level by rpoB sequencing: the Acinetobacter baumannii group (ABG; 101 A. baumannii, 43 A. nosocomialis, 10 A. pittii isolates) was most commonly identified (82.4%), followed by Acinetobacter genomic species 13BJ/14TU (5.3%), A. ursingii (2.1%), A. soli (2.1%), A. bereziniae (1.1%), and A. junii (1.1%). Correct identification rates to the species group (ABG) level or the species level was comparable among the three systems (VITEK MS, 90.3%; VITEK 2, 89.2%; MicroScan, 86.9%). However, VITEK MS generated fewer misidentifications (0.6%) than VITEK 2 (10.8%) and MicroScan (13.1%) (P<0.001). In addition, VITEK MS demonstrated higher specificity (100%) for discrimination between ABG and non-ABG isolates than the other systems (both, 31.8%) (P<0.001).
CONCLUSIONS
The VITEK MS system is superior to the VITEK 2 and MicroScan systems for identification of Acinetobacter BSI isolates, with fewer misidentifications and better discrimination between the ABG and non-ABG isolates.

Keyword

VITEK MS; VITEK 2; MicroScan; Acinetobacter; Identification

MeSH Terms

Acinetobacter/*genetics/isolation & purification
Acinetobacter Infections/diagnosis/microbiology
Bacterial Proteins/genetics
Bacterial Typing Techniques/*instrumentation/*methods
Blood/*microbiology
DNA, Bacterial/*analysis/metabolism
Databases, Genetic
Humans
*Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
Bacterial Proteins
DNA, Bacterial