CEB - Centre of Biological Engineering, LIBRO - Laboratório de Investigação em Biofilmes Rosário Oliveira, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal.
Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
FEMS Microbiol Ecol. 2021 Aug 3;97(8). doi: 10.1093/femsec/fiab105.
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.
严格的溶菌噬菌体被认为是控制食源性病原体的有力工具。在控制产志贺毒素大肠杆菌（STEC）的生物防治中，需要解决以下安全问题：溶原性转换、噬菌体诱导产生志贺毒素、以及噬菌体不敏感突变体（BIMs）的出现/增殖。为了解决这些问题，分离并鉴定了两种新的溶菌噬菌体 vB_EcoS_Ace（Ace）和 vB_EcoM_Shy（Shy），以研究它们的生命周期、基因组序列和注释、pH 值稳定性以及控制 STEC 生长的效果。Ace 能有效控制宿主浮游细胞，且不会刺激 Stx 噬菌体的产生或志贺毒素的产生。噬菌体的单次剂量不会导致 BIMs 的选择。然而，当再次引入噬菌体时，在孵育 24 小时后检测到了 BIMs。获得耐药性与毒力降低有关，因为一部分 BIMs 不能与 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当。总的来说，这项工作表明噬菌体 Ace 是一种安全的生物防治剂，可以控制 STEC 污染，而 BIM 出现的负担并不会增加其在环境中的持久性和对人类的致病性的风险。
