Strictly lytic phages are considered powerful tools for biocontrol of foodborne pathogens. Safety issues needed to be addressed for the biocontrol of Shiga toxin-producing Escherichia coli (STEC) include: lysogenic conversion, Shiga toxin production through phage induction, and emergence/proliferation of bacteriophage insensitive mutants (BIMs). To address these issues, two new lytic phages, vB_EcoS_Ace (Ace) and vB_EcoM_Shy (Shy), were isolated and characterized for life cycle, genome sequence and annotation, pH stability and efficacy at controlling STEC growth. Ace was efficient in controlling host planktonic cells and did not stimulate the production of the Stx prophage or Shiga toxin. A single dose of phage did not lead to the selection of BIMs. However, when reintroduced, BIMs were detected after 24 h of incubation. The gain of resistance was associated with lower virulence, as a subset of BIMs failed to agglutinate with O157-specific antibody and were more sensitive to human serum complement. BIM's biofilm formation capacity and susceptibility to disinfectants was equal to that of the wild-type strain. Overall, this work demonstrated that phage Ace is a safe biocontrol agent against STEC contamination and that the burden of BIM emergence did not represent a greater risk in environmental persistence and human pathogenicity.

中文翻译：

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噬菌体 Ace 与产志贺毒素大肠杆菌在生防过程中的相互作用

严格裂解噬菌体被认为是食源性病原体生物防治的有力工具。产志贺毒素大肠杆菌(STEC) 的生物防治需要解决的安全问题包括：溶原转化、通过噬菌体诱导产生志贺毒素以及噬菌体不敏感突变体 (BIM) 的出现/增殖。为了解决这些问题，分离了两种新的裂解噬菌体 vB_EcoS_Ace (Ace) 和 vB_EcoM_Shy (Shy)，并对其生命周期、基因组序列和注释、pH 稳定性和控制 STEC 生长的功效进行了表征。Ace 可有效控制宿主浮游细胞，并且不会刺激 Stx 原噬菌体或志贺毒素的产生。单剂量的噬菌体不会导致 BIM 的选择。然而，当重新引入时，孵化 24 小时后检测到 BIM。耐药性的获得与较低的毒力相关，因为 BIM 的一部分无法与 O157 特异性抗体凝集，并且对人血清补体更敏感。BIM的生物膜形成能力和对消毒剂的敏感性与野生型菌株相同。总体而言，这项工作表明，噬菌体 Ace 是一种针对 STEC 污染的安全生物防治剂，并且 BIM 出现的负担并不代表环境持久性和人类致病性的更大风险。