Salmonella enterica serovar Typhimurium (S. Typhimurium [STM]) is a leading cause of nontyphoidal salmonellosis (NTS) worldwide. The pathogenesis of NTS has been studied extensively using a streptomycin‐pretreated mouse colitis model with the limited numbers of laboratory STM strains. However, the pathogenicity of the clinically isolated STM (STMC) strains endemic in Thailand in mice has not been explored. The aim of this study was to compare the pathogenicity of STMC strains collected from Northern Thailand with the laboratory STM (IR715) in mice. Five STMC isolates were obtained from the stool cultures of patients with acute NTS admitted to Maharaj Nakorn Chiang Mai Hospital in 2016 and 2017. Detection of virulence genes and sequence type (ST) of the strains was performed. Female C57BL/6 mice were pretreated with streptomycin sulfate 1 day prior to oral infection with STM. On Day 4 postinfection, mice were euthanized, and tissues were collected to analyze the bacterial numbers, tissue inflammation, and cecal histopathological score. We found that all five STMC strains are ST34 and conferred the same or reduced pathogenicity compared with that of IR715 in mice. A strain‐specific effect of ST34 on mouse gut colonization was also observed. Thailand STM ST34 exhibited a significant attenuated systemic infection in mice possibly due to the lack of spvABC‐containing virulence plasmid.

中文翻译：

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在小鼠结肠炎模型中来自泰国的临床肠炎沙门氏菌血清鼠伤寒分离株的致病性。

沙门氏菌鼠伤寒沙门氏菌（小号。鼠伤寒（STM）是全球非伤寒沙门氏菌病（NTS）的主要原因。NTS的发病机制已使用链霉素预处理的小鼠结肠炎模型进行了广泛的研究，其中使用的实验室STM菌株数量有限。但是，尚未研究泰国在泰国流行的临床分离的STM（STMC）毒株的致病性。这项研究的目的是比较从泰国北部收集的STMC菌株与实验室STM（IR715）在小鼠中的致病性。从2016年和2017年收治于Maharaj Nakorn清迈医院的急性NTS患者的粪便培养物中获得了5株STMC分离株。对菌株的毒力基因和序列类型（ST）进行了检测。在用STM口服感染前1天，将雌性C57BL / 6小鼠用硫酸链霉素进行预处理。感染后第4天，对小鼠实施安乐死，并收集组织以分析细菌数量，组织炎症和盲肠组织病理学评分。我们发现所有五个STMC菌株均为ST34，与IR715相比，小鼠具有相同或降低的致病性。还观察到了ST34对小鼠肠道定殖的菌株特异性作用。泰国STM ST34在小鼠中表现出明显的减毒全身感染，可能是由于缺乏包含spvABC的毒力质粒。