Gastrointestinal infections caused by nontyphoidal Salmonella (NTS) remain one of the main causes of foodborne illness worldwide. Within the multiple existing Salmonella enterica serovars, the serovar Rissen is rarely reported, particularly as a cause of human salmonellosis. Between 2015 and 2017, the Portuguese National Reference Laboratory of Gastrointestinal Infections observed an increase in the number of clinical cases caused by multidrug-resistant (MDR) S. enterica serovar Rissen, particularly from the Azores archipelago. In the present study, we analyzed by whole genome sequencing (WGS) all clinical, animal, food, and environmental isolates received up to 2017 in the Portuguese Reference Laboratories. As such, through a wgMLST-based gene-by-gene analysis, we aimed to identify potential epidemiological clusters linking clinical and samples from multiple sources, while gaining insight into the genetic diversity of S. enterica serovar Rissen. We also investigated the genetic basis driving the observed multidrug resistance. By integrating 60 novel genomes with all publicly available serovar Rissen genomes, we observed a low degree of genetic diversity within this serovar. Nevertheless, the majority of Portuguese isolates showed high degree of genetic relatedness and a potential link to pork production. An in-depth analysis of these isolates revealed the existence of two major clusters from the Azores archipelago composed of MDR isolates, most of which were resistant to at least five antimicrobials. Considering the well-known spread of MDR between gastrointestinal bacteria, the identification of MDR circulating clones should constitute an alert to public health authorities. Finally, this study constitutes the starting point for the implementation of the “One Health” approach for Salmonella surveillance in Portugal.

中文翻译：

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在葡萄牙亚速尔群岛检测到多重耐药沙门氏菌血清变种群。


非伤寒沙门氏菌(NTS) 引起的胃肠道感染仍然是全球食源性疾病的主要原因之一。在现有的多种肠道沙门氏菌血清型中，Rissen 血清型很少被报道，特别是作为人类沙门氏菌病的原因。 2015年至2017年间，葡萄牙国家胃肠道感染参考实验室观察到，由多重耐药（MDR）肠沙门氏菌Rissen引起的临床病例数量有所增加，特别是来自亚速尔群岛的病例。在本研究中，我们通过全基因组测序 (WGS) 分析了葡萄牙参考实验室截至 2017 年收到的所有临床、动物、食品和环境分离株。因此，通过基于 wgMLST 的逐基因分析，我们的目的是确定将临床和多个来源的样本联系起来的潜在流行病学集群，同时深入了解肠沙门氏菌Rissen 血清型的遗传多样性。我们还研究了导致观察到的多药耐药性的遗传基础。通过将 60 个新基因组与所有公开的 Rissen 血清型基因组进行整合，我们观察到该血清型内的遗传多样性程度较低。尽管如此，大多数葡萄牙分离株显示出高度的遗传相关性以及与猪肉生产的潜在联系。对这些分离株的深入分析揭示了亚速尔群岛存在两个由多重耐药分离株组成的主要菌群，其中大多数对至少五种抗菌药物具有耐药性。考虑到众所周知的耐多药在胃肠道细菌之间的传播，耐多药循环克隆的识别应引起公共卫生当局的警惕。 最后，这项研究构成了在葡萄牙实施沙门氏菌监测“One Health”方法的起点。