Exploring Bacterial Resistant Metabolism by Matrix-Assisted Laser Desorption Ionization-Mass Spectrometry Imaging

The inappropriate and excessive use of antibiotics for the treatment of bacterial infections has led to the increasing presence of resistant and multidrug-resistant bacteria both in hospital settings and in the community. Thus, understanding the metabolism of resistant bacteria is extremely important to combat them more efficiently. In this scenario, mass spectrometry imaging (MSI) is considered a promising technique for understanding the resistant characteristics of such bacteria and how they can potentially be treated. This process consists of the identification of different ions on the surface of the colonies and the identification of potential metabolites that characterize antibiotic resistance, upon comparison with susceptible bacteria of the same species. This work presents matrix-assisted laser desorption ionization-mass spectrometry imaging (MALDI-MSI) study of colonies of Methicillin-resistant Staphylococcus aureus, as a proof of concept of the technique for obtaining images of bacteria colonies. Images of methicillin-resistant and susceptible colonies of Staphylococcus aureus were obtained by a sublimation process to apply the MALDI matrix on the samples followed by MALDI-MSI analysis. Seventeen (17) potential metabolites were identified and spatially localized, such as N,N-dihydroxy-L-valine, 2-(4-Methylphenyl)ethylamine, 3,4-Dihydroxy-L-phenylalanine, 2-Methyl-hexanoic acid, threonine, Arginine, Aureusimine and Glycyl-D-asparagine. Thus, this study reinforces the potential of MALDI-MSI for identification of metabolites synthesized by different strains of Staphylococcus aureus bacteria.