Abstract
BackgroundReptile-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 findingsWe 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.SignificanceWe 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.
Highlights
Salmonella is a clinically relevant bacterial pathogen that poses a significant burden upon public health worldwide [1,2,3,4]
The bacteria have the ability to colonise the gastrointestinal tract of a wide range of animals including reptiles
We showed that the majority of venomous snakes (91%) in our study carry Salmonella, and used bacterial genomics to assign two thirds of isolates to the S. enterica subspecies enterica which is associated with human salmonellosis
Summary
Salmonella is a clinically relevant bacterial pathogen that poses a significant burden upon public health worldwide [1,2,3,4]. Two groups of Salmonella serovars have clinical relevance with distinct host-specificity and disease manifestations. Typhoidal Salmonella is restricted to human hosts and presents as a systemic infection, resulting in an estimated 223,000 fatalities per annum [5]. Nontyphoidal Salmonella typically manifests as a self-limiting gastrointestinal disease in otherwise healthy individuals around the world, causing an annual global disease burden of 93.8 million cases and 155,000 deaths [3]. Reptile-associated Salmonella bacteria are a major, but often neglected cause of both gastrointestinal and bloodstream infection in humans globally. We investigated the prevalence and diversity of Salmonella in a collection of venomous snakes and non-venomous reptiles
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