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

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pISSN 2288-0585 eISSN 2288-6850

Application of Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry to Screen the Extended-Spectrum β-Lactamase-Producing ST131 Escherichia coli Strains

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2016 September, Volume 19, Issue 3, pages 65-69.

https://doi.org/10.5145/ACM.2016.19.3.65

Application of Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry to Screen the Extended-Spectrum β-Lactamase-Producing ST131 Escherichia coli Strains

Young Ah Kim1, Dongeun Yong2, Yong Ha In3, Hyung Soon Park3, Kyungwon Lee2
1Department of Laboratory Medicine, National Health Insurance Service Ilsan Hospital, Goyang, 2Department of Laboratory Medicine and Research Institute of Bacterial Resistance, Yonsei University College of Medicine, 3R&D Center, ASTA Inc, Suwon, Korea

Abstract

Background: Sequence type 131 (ST131) O25b serogroup Escherichia coli, producing CTX-M type extended-spectrum β-lactamase (ESBL), is a major clone involved in worldwide pandemic spread in both community- and healthcare-associated infections. Recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has become a routine tool for the identification of bacteria in many laboratories. This study aimed to assess the performance of MALDI-TOF MS for the screening of ESBL-producing E. coli ST131 in a rapid, inexpensive, and simple way.

Methods: A total 26 clinical E. coli, isolated from blood between 2013 and 2014, were used. The characteristics are ST131-O25b ESBL producers (n=6), ST131-O16 ESBL producers (n=4), non-ST131 ESBL producers (n=11), and non-ST131 non-ESBL producers (n=5). Specific biomarker peaks to distinguish the ST131 clonal group from others were investigated by MicroIDSys (ASTA, South Korea) and ASTA Tinkerbell 2.0 software.

Results: A peak at 9,713 m/z peak is useful to screen for ST131 E. coli, regardless of serogroup O25 or O16, showing a sensitivity of 100%, specificity of 56.2%, positive predictive value of 58.8%, and negative predictive value of 100% when using a relative intensity cutoff of 15%.

Conclusion: We can screen for ST131 E. coli using MicroIDSys (ASTA), MALDI-TOF MS in a rapid, inexpensive, and simple way. However, other confirmatory tests are needed to confirm ST131 E. coli due to the low specificity of this method. (Ann Clin Microbiol 2016;19:65-69)

Keywords

Escherichia coli, Extended-spectrum β– lactamase, Matrix-assisted laser desorption ionization time-of-flight mass spectrometry, Sequence type 131, Serogroup O16, Serogroup O25b