MALDI-TOF MS Approaches for the Identification of the Susceptibility of Extended-Spectrum β-Lactamases in Escherichia coli

The increase in multidrug-resistant microorganisms that produce extended-spectrum beta-lactamases (ESBLs) and carbapenemases is a serious problem worldwide. Recently, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) has been used for the rapid detection of antibiotic-resistant bacteria. The objective of this study was to establish a method to detect ESBL-producing Escherichia coli by monitoring the hydrolyzation of cefotaxime (CTX) using MALDI-TOF MS. According to the ratio of the peak intensity of CTX and hydrolyzed-CTX-related compounds, the ESBL-producing strains could be clearly distinguished after 15 min of incubation. Moreover, the minimum inhibitory concentration (MIC) values for E. coli were 8 mu g/mL and lower than 4 mu g/mL, which could be distinguished after 30 min and 60 min of incubation, respectively. The enzymatic activity was determined using the difference in the signal intensity of the hydrolyzed CTX at 370 Da for the ESBL-producing strains incubated with or without clavulanate. The ESBL-producing strains with low enzymatic activity or bla(CTX-M) genes could be detected by monitoring the hydrolyzed CTX. These results show that this method can rapidly detect high-sensitivity ESBL-producing E. coli.

Automated summary

The worldwide increase in multidrug-resistant microorganisms that produce extended-spectrum beta-lactamases (ESBLs) and carbapenemases is a serious public health concern. Recently, matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid method for detecting antibiotic-resistant bacteria. This study aimed to establish a method to detect ESBL-producing Escherichia coli using MALDI-TOF MS by monitoring the hydrolyzation of cefotaxime (CTX). The results showed that this method can rapidly and accurately detect ESBL-producing E. coli with high sensitivity.