Department of Microbiology, Osaka City Institute of Public Health and Environmental Sciences, 8-34, Osaka 543-0026, Japan.
J Food Prot. 2013 Jul;76(7):1179-86. doi: 10.4315/0362-028X.JFP-12-225.
Listeria monocytogenes is a foodborne pathogen that causes the potentially life-threatening illness listeriosis. Previously, a few clones of L. monocytogenes persisting in a cold-smoked fish processing plant were isolated from the plant's products continuously. To evaluate the role of biofilms in the persistence of L. monocytogenes strains specific to this plant, the abilities of the persistent strain (PS) and transient strain (TS) of L. monocytogenes found in this plant to form biofilms were compared, as was resistance to the sanitizing effects of benzalkonium chloride (BC). The PS produced more biofilm than the TS in 48 h. The half-maximal effective concentration (EC50), the BC concentration at which the ATP bioluminescence of each bacterial strain decreased by 50 % relative to its maximum activity, was about 150-fold higher in the PS than in the TS. In contrast, when these values were measured in organisms in a planktonic state, the EC50 of the PS was only 2.2-fold higher than that of the TS. Extracellular polymeric substances (EPS) were extracted from biofilms, and the glucose content of these biofilms was determined with the phenol-sulfuric acid method to estimate the quantity of EPS. The total amount of EPS in the PS biofilm was higher than that in the TS biofilm. These findings suggest that the PS produces greater amounts of biofilm and EPS than the TS, which results in greater resistance of the PS to disinfectants. The persistence of the strain in the fish processing plant might be attributable to these properties.
单增李斯特菌是一种食源性致病菌，可引起潜在的危及生命的李斯特菌病。此前，从该工厂的产品中连续分离到持续存在于冷熏鱼加工厂的少数单增李斯特菌克隆。为了评估生物膜在该工厂特有单增李斯特菌菌株持续存在中的作用，比较了从该工厂发现的持续存在菌株（PS）和瞬态菌株（TS）形成生物膜的能力，以及对苯扎氯铵（BC）消毒效果的抗性。PS 在 48 小时内产生的生物膜比 TS 多。PS 的半数最大有效浓度（EC50），即每个细菌菌株的 ATP 生物发光相对于其最大活性降低 50%时的 BC 浓度，比 TS 高约 150 倍。相比之下，当在浮游状态下的生物体中测量这些值时，PS 的 EC50 仅比 TS 高 2.2 倍。从生物膜中提取细胞外聚合物质（EPS），并用苯酚-硫酸法测定这些生物膜的葡萄糖含量，以估计 EPS 的量。PS 生物膜中的 EPS 总量高于 TS 生物膜。这些发现表明，PS 比 TS 产生更多的生物膜和 EPS，这导致 PS 对消毒剂的抗性更大。该菌株在鱼类加工厂的持续存在可能归因于这些特性。
