Salmonella enterica subspecies diarizonae serovar 61:(k):1, 5, (7) (sheep associated S. diarizonae, SASd) is the most common Salmonella serotype identified in sheep flocks. Despite the involvement with animal and human infections, there is limited information regarding virulence profiles of SASds and their antibiotic resistance gene complement, particularly for those circulating in the U.S. In this study, we genetically characterized three SASds, 20-265, 20-269, and 20-312, isolated from sheep placental tissues during an abortion storm affecting a flock in Connecticut during 2020. SASds were the only bacteria isolated from analyzed sheep tissues. The isolates were sensitive to all the antibiotics tested, but all these SASd isolates carry the aminoglycoside resistance gene, aac(6′)-Iaa, and a chromosomal substitution in the parC gene. The proportion of pseudogenes (5.3-5.5%) was similar among the isolates, and these SASds carry IncX1 type plasmids. Comparing with the SASds isolates from Enterobase, the three isolates showed an identical genomic virulence profile carrying virulence genes in the conserved set of other SASd isolates except for steC, iagB, iacP, sseI, and slrP genes. In the SNP-based phylogenetic analysis, SASd sequences were grouped into group A-C, and the group C was further subdivided into subgroup C1-C6. The three isolates clustered with other SASd isolates from the U.S. and Canada in subgroup C6. SASd isolates in the identical phylogenetic groups tended to have similar geographical origin. The results of our study did not provide conclusive evidence about which are the genetic traits that trigger SASds to become virulent in sheep, but our data will provide a point for comparative studies of this Salmonella serovar.

Salmonella enterica subspecies diarizonae serovar 61:(k):1, 5, (7) (sheep associated S. diarizonae, SASd) 是最常见的沙门氏菌在羊群中鉴定的血清型。尽管涉及动物和人类感染，但关于 SASd 的毒力谱及其抗生素抗性基因补充的信息有限，特别是对于在美国流行的那些在本研究中，我们对三种 SASd 进行了遗传表征，20-265、20-269、和 20-312，在 2020 年影响康涅狄格州一个羊群的流产风暴期间从绵羊胎盘组织中分离出来。SASds 是唯一从分析的绵羊组织中分离出的细菌。这些分离株对所有测试的抗生素都敏感，但所有这些 SASd 分离株都携带氨基糖苷类抗性基因aac(6')-Iaa和parC 中的染色体替换基因。分离株之间假基因的比例（5.3-5.5%）相似，这些SASds携带IncX1型质粒。与来自 Enterobase 的 SASds 分离株相比，除了steC、iagB、iacP、sseI和slrP之外，这三个分离株显示出相同的基因组毒力谱，在其他 SASd 分离株的保守集中携带毒力基因基因。在基于SNP的系统发育分析中，SASd序列分为AC组，C组进一步细分为C1-C6亚组。这三个分离株与来自美国和加拿大的其他 SASd 分离株聚集在 C6 亚组中。相同系统发育组中的 SASd 分离株往往具有相似的地理起源。我们的研究结果没有提供确凿的证据，说明哪些遗传特征会触发 SASd 在绵羊中变得有毒，但我们的数据将为这种沙门氏菌血清型的比较研究提供一个点。