A Novel Targeted Approach in Disinfection and Decontamination Through Inhibition of Specific Stress Resistance Mechanisms in Listeria monocytogenes

Normally disinfection uses a mix of various compounds that the affect survival of microorganisms. Acidic disinfectants, normally, use compounds that have high pKa to ensure a higher bactericidal effect. Our work demonstrates a novel approach in decontamination and disinfection regimes where specific molecular acid resistance systems are inhibited, aiming to eliminate microorganisms under acidic conditions. Despite the importance of the Glutamate Decarboxylase (GAD) system for survival of Listeria monocytogenes and other pathogens under acidic conditions, its potential inhibition by specific compounds that could lead to their elimination from foods or food preparation premises has not been studied. This work investigates the effects of maleic acid on the acid resistance of L. monocytogenes. Maleic acid was shown to have a higher antimicrobial activity under acidic conditions than other organic acids. It was able to significantly increase the sensitivity of L. monocytogenes strains to acidic conditions with more pronounced effects on strains with higher GAD activity. Maleic acid affected the extracellular gamma-aminobutyric acid (GABA) levels, while it did not affect the intracellular GABA levels. All data suggest that there is a major impact by maleic acid; mainly on the GadD2 activity, which is shown in cell lysates. Furthermore, we found that maleic acid is able to remove biofilms of L. monocytogenes. Maleic acid is able to inhibit the glutamate decarboxylase of L. monocytogenes; and, as such, it can significantly enhance the antibacterial effect of acidic conditions. The above properties, combined with the ability to remove biofilms, make this compound a great candidate for disinfection and decontamination regimes.