Ann Clin Microbiol.  2016 Sep;19(3):65-69. 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

• Kim YA
• Yong D
• In YH
• Park HS
• Lee K

• KMID: 2353042
• DOI: http://doi.org/10.5145/ACM.2016.19.3.65

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.

Keyword

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

MeSH Terms

Bacteria
Clone Cells
Escherichia coli*
Escherichia*
Mass Screening
Mass Spectrometry*
Methods
Pandemics
Sensitivity and Specificity
Serogroup

Figure

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  Fig. 1. Visual inspection of 9,713 m/z for ST131 E. coli with relative intensity 15% (cutoff). Test performance: sensitivity 100%, specificity 56.2%, positive-predictive value 58.8%, and negative-predictive vale 100%.

Reference

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