Antimicrobial effect of chitosan and extracellular metabolites of Pediococcus pentosaceus CM175 against Salmonella Typhimurium and Escherichia coli O157:H7

Abstract

AbstractFoodborne illness outbreaks caused by consuming cantaloupe melon contaminated with Salmonella spp. and Escherichia coli O157:H7 are recurrent. The objective of this work was to investigate the antimicrobial effect of the combination of chitosan (Q) and extracellular metabolites of Pediococcus pentosaceus CM175 (EmPp) on the surface of cantaloupe against E. coli O157:H7 and Salmonella Typhimurium. The minimum inhibitory and bactericide concentrations (MIC and MBC) of Q and EmPp were determined by the method of microdilution in broth and viability in plate, respectively. The antimicrobial effect derived from the combination of Q and EmPp was evaluated using the chessboard technique. The antimicrobial activity of the different treatments in cantaloupe was performed employing plate counting. The viability and membrane integrity of S. Typhimurium and E. coli O157:H7 after treatments application were observed by fluorescence microscopy. The results showed that MIC and MBC of Q against S. Typhimurium were 0.1% and 0.7%, respectively; 0.004% and 0.03% for E. coli O157:H7, respectively; for EmPp, MIC was 8.0% and MBC was 10% for both bacteria. The combination of 0.1% Q and 6.6% EmPp against S. Typhimurium and 0.01% Q and 5.0% EmPp against E. coli O157:H7 showed an additive effect. The highest reductions of S. Typhimurium and E. coli O157:H7 in cantaloupe were exerted by the combinations of 0.1% Q with 6.6% EmPp and 0.01% Q with 5.0% EmPp, respectively. These results show that combination of Q and EmPp could be an effective and promising alternative against the tested pathogens.