Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
Animal Health Department, Chester Zoo, Cheshire, United Kingdom.
PLoS Negl Trop Dis. 2019 Jun 4;13(6):e0007169. doi: 10.1371/journal.pntd.0007169. eCollection 2019 Jun.
Reptile-associated Salmonella bacteria are a major, but often neglected cause of both gastrointestinal and bloodstream infection in humans globally. The diversity of Salmonella enterica has not yet been determined in venomous snakes, however other ectothermic animals have been reported to carry a broad range of Salmonella bacteria. We investigated the prevalence and diversity of Salmonella in a collection of venomous snakes and non-venomous reptiles.
METHODOLOGY/PRINCIPLE FINDINGS: We used a combination of selective enrichment techniques to establish a unique dataset of reptilian isolates to study Salmonella enterica species-level evolution and ecology and used whole-genome sequencing to investigate the relatedness of phylogenetic groups. We observed that 91% of venomous snakes carried Salmonella, and found that a diverse range of serovars (n = 58) were carried by reptiles. The Salmonella serovars belonged to four of the six Salmonella enterica subspecies: diarizonae, enterica, houtanae and salamae. Subspecies enterica isolates were distributed among two distinct phylogenetic clusters, previously described as clade A (52%) and clade B (48%). We identified metabolic differences between S. diarizonae, S. enterica clade A and clade B involving growth on lactose, tartaric acid, dulcitol, myo-inositol and allantoin.
We present the first whole genome-based comparative study of the Salmonella bacteria that colonise venomous and non-venomous reptiles and shed new light on Salmonella evolution. Venomous snakes examined in this study carried a broad range of Salmonella, including serovars which have been associated with disease in humans such as S. Enteritidis. The findings raise the possibility that venomous snakes could be a reservoir for Salmonella serovars associated with human salmonellosis.
与爬行动物相关的沙门氏菌是造成全球人类胃肠道和血液感染的一个主要但经常被忽视的原因。然而，其他变温动物已经被报道携带广泛的沙门氏菌，但是蛇类的沙门氏菌 enterica 多样性尚未确定。我们调查了毒蛇和非毒蛇爬行动物中沙门氏菌的流行情况和多样性。
方法/主要发现：我们使用选择性富集技术的组合，建立了一组独特的爬行动物分离株数据集，以研究沙门氏菌 enterica 种水平的进化和生态，并使用全基因组测序来研究系统发育群的亲缘关系。我们观察到 91%的毒蛇携带沙门氏菌，并且发现多种血清型（n = 58）被爬行动物携带。沙门氏菌血清型属于沙门氏菌 enterica 的四个亚种：迪亚里宗纳亚种、肠道亚种、胡塔那亚种和萨拉马亚种。肠道亚种分离株分布在两个不同的系统发育群中，之前被描述为 A 群（52%）和 B 群（48%）。我们确定了 S. diarizonae、A 群和 B 群 S. enterica 之间的代谢差异，涉及乳糖、酒石酸、dulcitol、肌醇和尿囊素的生长。
我们首次基于全基因组对寄生在毒蛇和非毒蛇上的沙门氏菌进行了比较研究，为沙门氏菌的进化提供了新的视角。本研究中检查的毒蛇携带广泛的沙门氏菌，包括与人类沙门氏菌病相关的血清型，如 S. Enteritidis。这些发现增加了毒蛇可能成为与人类沙门氏菌病相关的沙门氏菌血清型的储存库的可能性。
