Variations in tolerance of Listeria monocytogenes to nisin, pediocin PA-1 and bavaricin A.

A collection of 381 Listeria monocytogenes strains was examined for strain variations in nisin and pediocin sensitivity at three different concentrations on Tryptic Soya Agar. Two of the strains were able to grow on agar plates containing 500 IU nisin ml-1. These strains were characterized as having an enhanced nisin tolerance. Twenty strains had normal growth on agar plates containing 1600 AU pediocin ml-1 and higher. These strains were characterized as pediocin-resistant. Another 34 strains, characterized as having enhanced tolerance, exhibited inhibited growth at 1600 AU pediocin ml-1. Bavaricin sensitivity, examined for 22 strains of L. monocytogenes, correlated with the pediocin sensitivity of the strains. It is therefore assumed that there is accordance between the pediocin and bavaricin sensitivity of the remaining strains. Cross-resistance between nisin and pediocin/bavaricin was not found.