Henderson L O, Erazo Flores B J, Skeens J, Kent D, Murphy S I, Wiedmann M, Guariglia-Oropeza V
Department of Food Science, Cornell University, Ithaca, NY, United States.
Universidad de Puerto Rico, Mayagüez, Puerto Rico.
Front Microbiol. 2020 Apr 9;11:635. doi: 10.3389/fmicb.2020.00635. eCollection 2020.
The growth of on refrigerated, ready-to-eat food products is a major health and economic concern. The natural antimicrobial nisin targets the bacterial cell wall and can be used to inhibit growth on cheese. Cell wall composition and structure, and therefore the efficacy of cell wall acting control strategies, can be severely affected by environmental and stress conditions. The goal of this study was to determine the effect of a range of pH and temperatures on the efficacy of nisin against several strains of in a lab-scale, cheese model. Cheese was made with or without the addition of nisin at different pH and then inoculated with ; numbers were quantified after 1, 7, and 14 days of incubation at 6, 14, or 22°C. While our data show that nisin treatment is able to reduce numbers, at least initially, growth of this pathogen can occur even in the presence of nisin, especially when cheese is stored at higher temperatures. Several environmental factors were found to affect nisin efficacy against . For example, nisin is more effective when cheese is stored at lower temperatures. Nisin is also more effective when cheese is made at higher pH (6 and 6.5), compared to cheese made at pH 5.5, and this effect is at least partially due to the activity of cell envelope modification genes and . Serotype was also found to affect nisin efficacy against ; serotype 4b strains showed lower susceptibility to nisin treatment compared to serotype 1/2 strains. Overall, our results highlight the importance of considering environmental conditions specific to a food matrix when developing and applying nisin-based intervention strategies against .
冷藏即食食品上[某种细菌]的生长是一个重大的健康和经济问题。天然抗菌剂乳酸链球菌素作用于细菌细胞壁，可用于抑制奶酪上[该细菌]的生长。细胞壁的组成和结构，以及因此细胞壁作用控制策略的功效，会受到环境和应激条件的严重影响。本研究的目的是在实验室规模的奶酪模型中，确定一系列pH值和温度对乳酸链球菌素针对几种[该细菌]菌株的功效的影响。制作奶酪时在不同pH值下添加或不添加乳酸链球菌素，然后接种[该细菌]；在6、14或22°C下培养1、7和14天后对[该细菌]数量进行定量。虽然我们的数据表明乳酸链球菌素处理能够减少[该细菌]数量，至少在最初阶段如此，但即使存在乳酸链球菌素，这种病原体仍可能生长，尤其是当奶酪储存在较高温度下时。发现几个环境因素会影响乳酸链球菌素对[该细菌]的功效。例如，奶酪在较低温度下储存时，乳酸链球菌素更有效。与在pH 5.5制作的奶酪相比，在较高pH值（6和6.5）下制作奶酪时，乳酸链球菌素也更有效，这种效果至少部分归因于细胞包膜修饰基因[具体基因1]和[具体基因2] 的活性。还发现血清型会影响乳酸链球菌素对[该细菌]的功效；与1/2血清型菌株相比，4b血清型菌株对乳酸链球菌素处理的敏感性较低。总体而言，我们的结果突出了在制定和应用基于乳酸链球菌素的针对[该细菌]的干预策略时，考虑食品基质特定环境条件的重要性。
