Environmental Microbial and Food Safety Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, United States Department of Agriculture, Beltsville, Maryland.
Department of Veterinary and Biomedical Sciences, The Pennsylvania State University, University Park, Pennsylvania.
J Glob Antimicrob Resist. 2023 Jun;33:164-170. doi: 10.1016/j.jgar.2023.02.022. Epub 2023 Mar 9.
Shiga toxin-producing Escherichia coli (STEC) are globally significant foodborne pathogens. Dairy calves are a known reservoir of both O157 and non-O157 STEC. The objective of this study was to comprehensively evaluate the genomic attributes, diversity, virulence factors, and antimicrobial resistance gene (ARG) profiles of the STEC from preweaned and postweaned dairy calves in commercial dairy herds.
In total, 31 non-O157 STEC were identified as part of a larger study focused on the pangenome of >1000 E. coli isolates from the faeces of preweaned and postweaned dairy calves on commercial dairy farms. These 31 genomes were sequenced on an Illumina NextSeq500 platform.
Based on the phylogenetic analyses, the STEC isolates were determined to be polyphyletic, with at least three phylogroups: A (32%), B1 (58%), and G (3%). These phylogroups represented at least 16 sequence types and 11 serogroups, including two of the 'big six' serogroups, O103 and O111. Several Shiga toxin gene subtypes were identified in the genomes, including stx, stx, stx, stx, and stx. Using the ResFinder database, the majority of the isolates (>50%) were determined to be multidrug-resistant strains because they harboured genes conferring resistance to three or more classes of antimicrobials, including some of human health significance (e.g., β-lactams, macrolides, and fosfomycin). Additionally, non-O157 STEC strain persistence and transmission within a farm was observed.
Dairy calves are a reservoir of phylogenomically diverse multidrug-resistant non-O157 STEC. Information from this study may inform assessments of public health risk and guide preharvest prevention strategies focusing on STEC reservoirs.
产志贺毒素大肠杆菌（STEC）是全球重要的食源性病原体。奶牛犊牛是 O157 和非 O157 STEC 的已知宿主。本研究的目的是全面评估商业奶牛场中未断奶和断奶后奶牛犊牛 STEC 的基因组特征、多样性、毒力因子和抗生素耐药基因（ARG）谱。
作为一项更大规模研究的一部分，共鉴定出 31 株非 O157 STEC，该研究专注于来自商业奶牛场中未断奶和断奶后奶牛犊牛粪便中的 1000 多株大肠杆菌分离株的泛基因组。这些 31 个基因组在 Illumina NextSeq500 平台上进行了测序。
基于系统发育分析，STEC 分离株为多源，至少有三个进化枝：A（32%）、B1（58%）和 G（3%）。这些进化枝代表了至少 16 个序列类型和 11 个血清群，包括两个“六大”血清群 O103 和 O111。在基因组中鉴定出了几种志贺毒素基因亚型，包括 stx、stx、stx、stx 和 stx。使用 ResFinder 数据库，大多数分离株（>50%）被确定为多药耐药株，因为它们携带赋予对三种或更多类抗生素耐药的基因，包括一些对人类健康有意义的抗生素（如β-内酰胺类、大环内酯类和磷霉素）。此外，还观察到非 O157 STEC 菌株在农场内的持续存在和传播。
奶牛犊牛是具有不同遗传背景的多药耐药非 O157 STEC 的宿主。本研究的信息可能会影响对公共卫生风险的评估，并指导针对 STEC 宿主的收获前预防策略。
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