Martínez Beatriz, Bravo Diego, Rodríguez Ana
Instituto de Productos Lácteos de Asturias, Consejo Superior de Investigaciones Cientificas, 33300 Villaviciosa, Asturias, Spain.
J Food Prot. 2005 Nov;68(11):2383-8. doi: 10.4315/0362-028x-68.11.2383.
Wild Listeria isolates representing serovars found in artisanal cheeses commercialized in Asturias (northern Spain) were assessed for their susceptibility to several bacteriocins. Pediocin PA-1 was the most active bacteriocin followed by enterocin AS-48, nisin, and plantaricin C. However, some Listeria monocytogenes and Listeria innocua strains were already highly resistant to PA-1. Among the wild L. monocytogenes populations, the frequency of development of nisin resistance ranged from 10(-6) up to 10(-3), depending on the strain. Highly stable mutants with increased nisin resistance (two- to fourfold) were isolated and tested for potential cross-resistance to lysozyme, EDTA, and various NaCl concentrations and pH values. All mutants were cross-resistant to lysozyme but sensitive to EDTA. In contrast, no clear correlation could be established between nisin resistance and an altered susceptibility to NaCl or pH changes. Nisin-resistant variants were able to survive and even to multiply in milk fermented by a nisin-producing Lactococcus, but the growth of the wild-type strain was inhibited. The different phenotypes evaluated in this study are indicative of the unpredictability of the consequences of the development of nisin resistance in a dairy environment. This resistance should be considered when making a risk assessment of the long-term use of nisin to control L. monocytogenes.
对从西班牙北部阿斯图里亚斯商业化销售的手工奶酪中分离出的代表不同血清型的野生李斯特菌菌株，评估了它们对几种细菌素的敏感性。片球菌素PA-1是最具活性的细菌素，其次是肠球菌素AS-48、乳链菌肽和植物乳杆菌素C。然而，一些单核细胞增生李斯特菌和无害李斯特菌菌株已经对PA-1高度耐药。在野生单核细胞增生李斯特菌群体中，乳链菌肽耐药性的产生频率范围为10^(-6)至10^(-3)，具体取决于菌株。分离出了对乳链菌肽耐药性增强（两到四倍）的高度稳定突变体，并测试了它们对溶菌酶、乙二胺四乙酸（EDTA）以及不同氯化钠浓度和pH值的潜在交叉耐药性。所有突变体对溶菌酶都有交叉耐药性，但对EDTA敏感。相比之下，乳链菌肽耐药性与对氯化钠或pH变化敏感性改变之间没有明确的相关性。耐乳链菌肽变体能够在由产乳链菌肽的乳酸乳球菌发酵的牛奶中存活甚至繁殖，但野生型菌株的生长受到抑制。本研究中评估的不同表型表明，在乳制品环境中乳链菌肽耐药性产生的后果具有不可预测性。在对长期使用乳链菌肽控制单核细胞增生李斯特菌进行风险评估时，应考虑这种耐药性。
