A step towards the discrimination of beta-lactamase-producing clinical isolates of Enterobacteriaceae and Pseudomonas aeruginosa by MALDI-TOF mass spectrometry

Abstract

SummaryBackgroundMatrix-Assisted Laser-Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) has already proven to be a powerful tool for species identification in microbiological laboratories. As adequate and rapid screening methods for antibiotic resistance are crucially needed, the present study investigated the discrimination potential of MALDI-TOF MS among extended-spectrum-beta-lactamase (ESBL) or metallo-beta-lactamases- (MBL) producing and the nonproducing strains of Escherichia coli (n=19), Klebsiella pneumoniae (n=19), and Pseudomonas aeruginosa (n=38), respectively.Material/MethodsWe used a MALDI-TOF MS protocol, usually applied for species identification, in order to integrate a screening method for beta-lactamases into the routine species identification workflow. The acquired spectra were analyzed by visual inspection, statistical similarity analysis and support vector machine (SVM) classification algorithms.ResultsNeither visual inspection nor mathematical similarity analysis allowed discrimination between spectra of beta-lactamase-producing and the nonproducing strains, but classification within a species by SVM-based algorithms could achieve a correct classification rate of up to 70%.ConclusionsThis shows that MALDI-TOF MS has definite potential to discriminate antibiotic-resistant strains due to ESBL and MBL production from nonproducing strains, but this performance is not yet sufficiently reliable for routine microbiological diagnostics.

Evaluation of the βLacta Test, a Rapid Test Detecting Resistance to Third-Generation Cephalosporins in Clinical Strains of Enterobacteriaceae

“…Moreover, the continuous discovery of new ESBL has decreased interest in these techniques because of their limited coverage of the whole range of variants. Matrix-assisted laser desorption ionizationtime of flight (MALDI-TOF) mass spectrometry was recently proposed to detect antibiotic resistance mechanisms (11) but is to date not reliable enough for routine diagnosis (12,13).…”

Incidence of fecal Enterobacteriaceae producing broad-spectrum beta-lactamases in patients with hematological malignancies

“…12 ). The strains were selected in such a manner that from each patient, a single strain of each species isolated as the first one was included.…”

Recent Technology of Clinical Microbiology; Whole Genome Sequencing (WGS) and Matrix-Assisted, Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS)

“…A specific antimicrobial resistance gene can be detected by real-time polymerase chain reaction (RT-PCR), microarray assay or fluorescence in situ hybridization (FISH) and beta-lactamases or carbapenemases have been detected using MALDI-TOF [11,12]. In MDR species such as MRSA, VRE, MDR Enterobacteriaceae, MDR Pseudomonas and Acinetobacter, WGS detects an antimicrobial resistome such as ESBLs or carbapenemases by SNP-level analysis, contributing to antimicrobial therapy.…”

“…Detection of beta-lactamase and carbapenemase: ESBL or carbapenemase has been detected using MALDI-TOF by analyzing mass peak [11]. When observing another method for the detection of carbapenemase, isolates were incubated with ertapenem; the results were considered positive revealing carbapenem hydrolysis when the peak at m/z 475 disappeared completely [12,50].…”

“…Philippe et al reported that they had used MALDI-TOF for direct identification in blood culture vials, which shortened the procedure [10]. Moreover, beta-lactamases or carbapenemases can be detected using MALDI-TOF [11,12].…”