Use of matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) to detect carbapenem-resistant Enterobacteriaceae.

Abstract

Antimicrobial drug resistance is increasing worldwide at a frightening rate and is found among different species of bacteria causing nosocomial and community-acquired infections. Carbapenem-resistant Enterobacteriaceae (CRE’s) are one of the multi-drug resistant bacteria increasingly reported in the past decade, leaving the health care system unable to control the spread of antibiotic-resistant infections. A rapid and efficient method to identify drug resistant bacteria could advance the containment of this scourge. We thus investigated the use of MALDI-TOF MS technology, recognized as an accurate method for microorganism identification, as a potential tool for the detection of CRE based on the protein profiling for specific fingerprints. From 24 hours sub-cultured bacterial isolates known to carry and/or express single genes of a variety of carbapenemases, proteins were extracted using the formic acid ethanol extraction method and subjected to MS-based identification by MALDI-TOF MS Biotyper technology. The mass spectrometry spectra were then analyzed employing the programmed software flexAnalysis version 3.4 build 70 and ClinProTools version 2.2 build 83 to detect carbapenemases. The spectra were subjected to visual inspection for specific peaks characterization. Despite their close relationship, the method was able to differentiate between CRE and susceptible bacteria. The differences within carbapenemases were better distinguishable by visual observation of specific biomarker peaks and the modified main spectrum (MSP) method demonstrated that these differences could be more obvious by focusing on matchless low intensity peaks. Although the differentiation of CRE remains a challenge using MALDI Biotyper MS based on the protein profiling, according to our data and pending further investigation in clinical isolates of CRE, MALDI-TOF MS has potential as a diagnostic tool for the rapid detection of these multi-drug resistant bacteria.