Zhu Junli, Liu Jingcong, Hong Xiaoli, Sun Yang
College of Food Science and Biotechnology, Zhejiang Gongshang University, Hangzhou, China.
Front Microbiol. 2022 Jun 10;13:885502. doi: 10.3389/fmicb.2022.885502. eCollection 2022.
Various pathogenic and spoilage bacteria frequently coexist in meat processing environments and can form multispecies biofilms, causing significant health and economic issues. Despite the prevalence and coexistence, only less is known about possible interactions between (LM) and spoilers like species, and their community-wide resistance against natural preservatives. This study evaluates the interactions between mono- or dual-species biofilms formed by LM and (PL), as well as the sensitivity of these bacteria in dual-species biofilms to ε-polylysine hydrochloride (ε-PLH) alone or combined with cinnamon essential oil (CEO). The results showed that the biofilm cell density of in dual species was higher ( < 0.05) than LM, constituting about 85% of the total population. More biofilms and exopolysaccharide both in mono- or dual species of the two psychrotrophic strains were greatly produced at 15°C than at 30°C. The biomass, biovolume, and thickness of dual-species biofilms were significantly lower than single PL biofilm when tested using crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy, indicating the competitive interactions between them prevail. Additionally, ε-PLH significantly reduced the biofilm development as mono- and dual species in a concentration-dependent manner, especially single LM biofilm, which was consistent with the decrease in autoinducer-2 (AI-2) activity. LM as dual-species biofilms exhibited lower sensitivity to ε-PLH than its mono-biofilm probably due to protective effect conferred by PL. ε-PLH in combination with CEO, at the maximum sublethal concentrations (MSCs), showed enhanced inhibitory activity against dual-species biofilm formation, as evidenced by thin spare spatial structures and reduced AI-2 activity. In addition, the preformed dual biofilms were dramatically eradicated following treatment with ε-PLH combined with CEO at higher than minimum inhibitory concentration in comparison with either of the compounds used alone, indicating the synergistic antibiofilm of the two preservatives. This study reveals the competitive interactions between the two strains in dual-species biofilms, in which the dominant PL significantly contributed toward the tolerance of LM to ε-PLH, and the use of combined preservatives shows it is an effective strategy to control the multispecies biofilms in meat processing.
多种致病细菌和腐败细菌经常共存于肉类加工环境中，并可形成多物种生物膜，从而引发重大的健康和经济问题。尽管它们普遍存在且共存，但对于单核细胞增生李斯特菌（LM）与诸如假单胞菌属（PL）等腐败菌之间可能存在的相互作用，以及它们对天然防腐剂的全群落抗性，人们了解得还较少。本研究评估了由LM和PL形成的单物种或双物种生物膜之间的相互作用，以及这些双物种生物膜中的细菌对单独的ε-聚赖氨酸盐酸盐（ε-PLH）或与肉桂精油（CEO）联合使用时的敏感性。结果表明，双物种生物膜中PL的细胞密度高于LM（P<0.05），约占总菌数的85%。这两种嗜冷菌株的单物种或双物种生物膜在15℃时比在30℃时产生更多的生物膜和胞外多糖。当使用结晶紫染色、共聚焦激光扫描显微镜和扫描电子显微镜进行测试时，双物种生物膜的生物量、生物体积和厚度显著低于单物种PL生物膜，这表明它们之间存在竞争相互作用。此外，ε-PLH以浓度依赖的方式显著减少了单物种和双物种生物膜的形成，尤其是单物种LM生物膜，这与自诱导物-2（AI-2）活性的降低一致。作为双物种生物膜的LM对ε-PLH的敏感性低于其单物种生物膜，这可能是由于PL提供的保护作用。ε-PLH与CEO联合使用，在最大亚致死浓度（MSCs）下，对双物种生物膜形成的抑制活性增强，稀疏的空间结构和降低的AI-2活性证明了这一点。此外，与单独使用任何一种化合物相比，用高于最低抑菌浓度的ε-PLH与CEO联合处理后，预先形成的双物种生物膜被显著根除，这表明这两种防腐剂具有协同抗生物膜作用。本研究揭示了双物种生物膜中两种菌株之间的竞争相互作用，其中占主导地位的PL显著有助于LM对ε-PLH的耐受性，并且联合使用防腐剂表明这是控制肉类加工中多物种生物膜的有效策略。
