Nisin Sensitivity Research Articles

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.

Antimicrobial action of nisin against Salmonella typhimurium lipopolysaccharide mutants.

The antimicrobial activity of nisin against outer membrane lipopolysaccharide mutants of Salmonella typhimurium LT2 was investigated. Nisin sensitivity was associated with the extent of saccharide deletions from the outer membrane core oligosaccharide. The results indicated that the core oligosaccharide in lipopolysaccharide plays a role in nisin sensitivity.

Nisin Sensitivity of Lactic Acid Bacteria Isolated from Cured and Fermented Meat Products

Thirty strains of lactic acid bacteria from different meat sources (bologna, summer sausage, thurlinger sausage, chicken loaf and bacon) were tested for nisin sensitivity. The maximum concentration of nisin permitting growth for 20 strains was 50 IU/ml. Lactobacilli classified as atypical were sensitive to <5 IU nisin/ml. These strains could not be induced to increase resistance by five transfers to media with increased nisin concentrations. The ten strains with the higher resistance to nisin were checked for nisinase activity. One strain, Lactobacillus brevis, showed weak nisinase activity and the rest were negative.

Further Studies on the Antibotulinal Effectiveness of Nisin in Acidic Media

ABSTRACTThe antibotulinal effectiveness of nisin in TPYG broth was increased somewhat by lowering the pH to pH 5.5. The ability of nisin to inhibit the outgrowth of strain 56A spores was markedly increase at pH 5.5 by comparison to its effectiveness at higher pHs observed in previous studies. The increased effectiveness of nisin at pH 5.5 was less notable for the strain 69A, 113B, and 213B spores. The nisin sensitivity of the type E spores was essentially unchanged from that observed in earlier studies at higher pHs. At pH 6, nisin levels of 5000 I.U./ml were insufficient to prevent spore outgrowth by C. botulinum in cooked meat medium. Comparatively, much lower levels of nisin were effective in preventing botulinal outgrowth in TPYG broth at pH 6. The decreased effectiveness of nisin in cooked meat medium may be due to the binding of nisin to meat particles, and this binding is apparently not affected by lowering the pH to pH 6.0.

Nisin sensitivity of Bacillus coagulans.

Nisin sensitivity of Bacillus coagulans.