Data_Sheet_2_Biological and genomic characterization of three psychrophilic Y. enterocolitica phages.xlsx

Yersinia (Y.) enterocolitica is an important foodborne pathogenic species that is mainly transmitted by the consumption of contaminated meat, particularly pork. To combat the bacteria along the food chain, the application of strictly lytic phages may be a promising tool. As the temperatures in the gut of animals and during food processing can differ significantly, a phage cocktail intended to be used for applications should comprise phages that are active at various temperatures. In this study, we isolated and characterized three phages with a myoviridal morphology (vB_YenM_P8, vB_YenM_P744 and vB_YenM_P778), which lysed the most important Y. enterocolitica serotypes O:3, O:9 and O:5,27 at a low multiplicity of infection (MOI) and at low temperatures down to 6°C. While vB_YenM_P8 is a member of the T4 family, vB_YenM_P744 and vB_YenM_P778 are novel phages that do not show relationship to known phages. The three phages were mixed in a cocktail with the already described phages vB_YenM_P281 and vB_YenP_Rambo. The cocktail revealed a strong lytic activity and lysed a mixture of Y. enterocolitica serotypes at room temperature (RT) within few hours with a reduction of up to 4.8 log10 units. Moreover, at even lower temperatures the mixture was significantly reduced after incubation overnight. The strongest reductions were determined at 6°C (4.0 log10 units) suggesting that the cocktail can lyse the psychrophilic Y. enterocolitica also during food processing. To determine possible phage resistance, 100 colonies that survived the infection by the phages were isolated and analysed regarding their serotype and phage susceptibility. Most isolates belonged to serotype O:9, but all of them were still sensitive to at least one phage of the cocktail.

小肠结肠炎耶尔森菌（Yersinia (Y.) enterocolitica）是一类重要的食源性致病菌，主要通过食用受污染的肉类（尤以猪肉为主）传播。为在食物链中防控该病原菌，严格裂解性噬菌体的应用或许是极具前景的防控手段。由于动物肠道内与食品加工过程中的温度差异显著，用于相关应用的噬菌体鸡尾酒（phage cocktail）应包含可在多种温度下发挥活性的噬菌体。本研究分离并鉴定了3株具有肌尾噬菌体形态（myoviridal morphology）的噬菌体：vB_YenM_P8、vB_YenM_P744与vB_YenM_P778。这些噬菌体可在低感染复数（multiplicity of infection, MOI）以及低至6℃的温度下，裂解最具代表性的小肠结肠炎耶尔森菌血清型O:3、O:9与O:5,27。其中vB_YenM_P8属于T4型噬菌体家族，而vB_YenM_P744与vB_YenM_P778则为与已知噬菌体无亲缘关联的新型噬菌体。研究团队将这3株噬菌体与已报道的噬菌体vB_YenM_P281和vB_YenP_Rambo混合制备成噬菌体鸡尾酒。该混合制剂展现出强劲的裂解活性，可在室温（room temperature, RT）下数小时内裂解多种小肠结肠炎耶尔森菌血清型的混合菌液，菌量降幅最高达4.8 log₁₀单位。此外，即便在更低温度下，该混合制剂经过夜孵育后仍可显著降低菌量；其中在6℃下测得的降幅最为显著（达4.0 log₁₀单位），表明该噬菌体鸡尾酒可裂解嗜冷性小肠结肠炎耶尔森菌，即便在食品加工过程中亦可发挥防控作用。为探究潜在的噬菌体抗性，本研究分离了100株经噬菌体感染后存活的菌落，并对其血清型及噬菌体敏感性进行了分析。结果显示，多数存活菌株属于血清型O:9，但所有菌株仍对该噬菌体鸡尾酒中至少1株噬菌体保持敏感性。