Efeito antibacteriano e antibiofilme de cafeína contra patógenos alimentares

Abstract

Foodborne illnesses (FBDs) are largely caused by bacteria such as Escherichia coli, Salmonella spp., and Listeria monocytogenes, which are frequently associated with foodborne outbreaks. These bacteria can be found in various foods, among which fruit juices can be contaminated by pathogenic and spoilage microorganisms. A significant problem in the food industry is the formation of bacterial biofilms, which are complex structures of microorganisms that adhere to surfaces and are resistant to removal, posing a major challenge to food safety. In this context, the search for natural and more effective antimicrobial and antibiofilm agents has been a trend. The objective of this study was to evaluate biofilm formation and the effectiveness of caffeine in inhibiting biofilms of L. monocytogenes, E. coli, S. Enteritidis, and S. Typhimurium in grape and apple juices. The Minimum Inhibitory Concentration (MIC) was quantified, and caffeine was used at concentrations equivalent to 1 and 2 times the MIC to test its effectiveness in planktonic cells and biofilms. The bacterial strains were subjected to bacterial killing kinetics assays exposed to caffeine, and biofilm formation was assessed using crystal violet (CV) staining. The quantification of exopolysaccharide (EPS) content was measured in the biofilm. Scanning Electron Microscopy (SEM) was performed for the Salmonella strains. Caffeine showed MICs of 9.37 mM (millimoles) for E. coli and S. Typhimurium, 18.75 mM for S. Enteritidis, and 37.5 mM for L. monocytogenes. Additionally, it caused a significant reduction in cell viability and biofilm biomass, with greater efficacy observed against L. monocytogenes compared to E. coli. The alkaloid was more effective in treating formed biofilms than during biofilm formation. In grape juice, microorganisms formed biofilms, with L. monocytogenes showing the highest formation. The image obtained by Scanning Electron Microscopy (SEM) confirmed the action of caffeine on the cell membrane of both Salmonella strains, evidencing cell disruption. Caffeine demonstrated potential as an alternative to control biofilms in the food industry, especially in fruit juices, and can be used to complement or replace existing chemical disinfectants.