TiO-Assisted Laser Desorption/Ionization Mass Spectrometry for Rapid Profiling of Candidate Metabolite Biomarkers from Antimicrobial-Resistant Bacteria

Antimicrobial resistance (AMR) is one of the most serious problems affecting public health and safety. It is crucial to understand antimicrobial resistance from the molecular level. In this work, TiO-assisted laser desorption/ionization (LDI) mass spectrometry (MS) was used for the fast metabolites analysis from intact bacterial cells to discriminate different strains of bacteria and to detect AMR. With the mass spectra of bacterial metabolites by TiO-LDI MS, multivariable analysis was performed for bacterial identification to determine distinctive metabolites as the potential biomarkers. The most statistically significant metabolites were screened out by the method and further identified using liquid-chromatography (LC) tandem MS (MS/MS). Robustness of our developed methods in bacterial taxonomy was demonstrated by iterative validation using 48 clinical samples. The strategy was further illustrated with three clinical strains of ESBL (extended-spectrum β-lactamase-resistant)-positive Escherichia. coli and four clinical strains of ESBL-negative ones. Eleven key metabolites were identified as potential biomarkers of ESBL-positive E. coli. We also implemented the pathway and network analysis on the key metabolites to prove the feasibility of our method in executing metabolomics analysis. Compared to the most prevalent techniques in a metabolomics study, such as LC-MS, gas chromatography MS, and nuclear magnetic resonance spectroscopy, the current method has advantages in its simple sample preparation and short analysis time, thereby fitting especially into clinical usages and fast analyses.