Differential Sensitivity of Clostridium botulinum Strains to Nisin is Not Biotype-Associated

The sensitivities of proteolytic and nonproteolytic Clostridium botulinum strains to nisin and other bacteriocins were investigated. Although there were statistically different nisin sensitivities among vegetative cells from 18 C. botulinum strains, these differences were not biotype-associated. When inoculated into tryptose peptone yeast extract glucose broth containing nisin at various levels, spores from strain 56 A were not inhibited at all by 100 IU/ml of nisin. About 2,500 IU/ml was required to inhibit growth for 30 d. In contrast, only 10 IU/ml was required to inhibit strain 169 for 30 d. Both strains were completely inhibited at the 10,000 IU/ml limit allowed in processed cheeses. Spores from strains having limited (strain 56A), moderate (strain 25675), or extreme (strain 169) nisin sensitivity were examined for bacteriocin-mediated inhibition by Lactococcus lactis 11454, Pediococcus pentosaceus 43200, P. pentosaceus 43201, and Lactobacillus plantarum BN using the spot-on-the-lawn method. While the differences in nisin sensitivity were confirmed, there was no statistically significant difference in their sensitivities to the bacteriocins produced by other lactic acid bacteria.