Natural variation in susceptibility of Listeria strains to class IIa bacteriocins

Thirty-one Listeria strains were tested for sensitivity to four class IIa b acteriocins, namely, enterocin A, mesentericin Y105, divercin V41, and pedi ocin AcH, and to nisin A. Class IIa bacteriocins displayed surprisingly sim ilar antimicrobial patterns ranging from highly susceptible to fully resist ant strains, whereas nisin A showed a different pattern in which all Lister ia strains were inhibited. Particularly, it was observed that the strain Li steria monocytogenes V7 could not be inhibited by any of the class IIa bact eriocins tested. These observations suggest that Listeria strains resistant to the whole range of class IIa bacteriocins may occur in natural environm ents, which could be of great concern with regard to the use of these pepti des as food preservatives.