Inhibition of Clostridium perfringens Spore Germination by the Synergistic Effects of the Natural Products Chitosan and Nisin

<i>Clostridium perfringens</i> is a spore-forming bacterium that causes food poisoning. Given the high heat resistance of its spores, natural antimicrobial agents are considered as alternatives to thermal processing strategies to inactivate or eliminate such spores from food products. A high chitosan concentration (0.2%) can effectively inhibit the growth of <i>C. perfringens</i> spores in cooked chicken meat, whereas nisin cannot (even at concentrations four times higher than those permitted: 250 μM). However, nisin is an effective inhibitor when in combination with other preservatives. Therefore, we evaluated the inhibitory effects of a chitosan-nisin combination on the germination, outgrowth, and vegetative growth of <i>C. perfringens</i> spores in laboratory medium and chicken meat. Among many tested concentration combinations, a 0.025% chitosan and 0.075% nisin mixture was found to be the most effective for inhibiting spore germination and outgrowth in laboratory medium. Furthermore, a mixture of chitosan-nisin, at 0.025% each, blocked the vegetative growth of <i>C. perfringens</i> spores. However, four-times higher concentrations of chitosan-nisin (0.1% each) were required to effectively inhibit <i>C. perfringens</i> spore germination in chicken meat. Collectively, our results suggest that the combination of chitosan and nisin can be considered as an alternative approach to control <i>C. perfringens</i> spore germination in meat products.