Listeria monocytogenes develops no resistance to ferulic acid after exposure to low concentrations

Antimicrobial agents have been used as additives to control the growth of Listeria monocytogenes. Although nisin has been used to inhibit the growth of L. monocytogenes in food products, exposure to this agent also poses a risk for the development of nisin resistance. Ferulic acid has also been extensively used for growth inhibition of L. monocytogenes, although no previous investigations on the development of ferulic acid resistance have been conducted. In the present study, we inoculated culture media containing one of these two antimicrobial agents with bacteria that had been previously exposed to these agents and assessed for any changes in resistance. The resistance of L. monocytogenes to nisin increased after exposure to 5 ppm nisin, and its survival rate against 20 ppm nisin improved. On the other hand, exposure to 1000 ppm ferulic acid did not increase ferulic acid resistance. The present study demonstrated that the concentration of added nisin must be considered carefully to achieve a sufficient effect. Ferulic acid, on the other hand, showed a minimal risk of producing resistant bacteria, thus allowing it to impart a stable effect.