Prevalence and phenotypic characterization of Salmonella enterica isolates from three species of wild marine turtles in Grenada, West Indies

Abstract

Background and Aim: Salmonella enterica causes enteric disease in mammals and may potentially be transmitted from marine turtles that shed the pathogen in the environment. Marine turtle-associated human salmonellosis is a potential public health concern in Grenada, as the island supports populations of leatherback turtles (Dermochelys coriacea), hawksbill turtles (Eretmochelys imbricata), and green turtles (Chelonia mydas) that interface with veterinarians and conservation workers, the local population, and the thousands of visitors that frequent the island yearly. To date, the prevalence of S. enterica has only been examined in a small subset of marine turtles in the Caribbean and no studies have been conducted in Grenada. The aim of this study was to quantify the prevalence of S. enterica in leatherback, hawksbill and green turtles in Grenada, characterize phenotypes and DNA profiles, and explore the potential risk to human health in the region. Materials and Methods: A total of 102 cloacal swabs were obtained from nesting leatherback turtles and foraging hawksbill and green turtles. Samples were cultured on enrichment and selective media and isolates were phenotypically characterized using serotyping, pulsed-phase gel electrophoresis, and antibiotic susceptibility. Enrichment broths were additionally screened by polymerase chain reaction (PCR) using S. enterica-specific primers. Results: S. enterica was cultured from 15/57 (26.3%) leatherback turtles, 0/28 hawksbill, and 0/17 green turtles. This included S. enterica serovars Montevideo, S. I:4,5,12:i:-, Salmonella Typhimurium, Salmonella Newport, S. I:6,7:-:-, and S. I:4,5,12:-:-. Five/15 leatherback turtles carried multiple serovars. Eight pulsotype groups were identified with multiple clustering; however, there was no clear association between pulsotype group and serotype profile. Five/71 isolates showed resistance to streptomycin or ampicillin. Twenty-one/57 leatherback turtles, 14/28 hawksbill turtles, and 8/17 green turtles tested positive for S. enterica by quantitative PCR. Conclusion: Nesting leatherback turtles actively shed S. enterica and poses a risk for zoonosis; however, the presence of viable pathogen in green and hawksbill species is unclear. These findings help elucidate the role of marine turtles as potential sources of zoonotic S. enterica and provide baseline data for one health research in Grenada and the wider Caribbean region.

Emergence and genomic characteristics of multi-drug-resistant Salmonella in pet turtles and children with diarrhoea

“…Notably, S. Thompson was the predominant serovar among all of the 46 pet turtle-associated isolates. This observation is in accordance with those reported from turtles in Spain (59.3 %) and from other studies in China (five provinces, 45.2 %; Shanghai, 19.4 %), but different from reports from the West Indies, where the dominant serovar is S. Montevideo [9,12,21,41]. Furthermore, nearly all of the S. Thompson isolates from pet turtles and children with diarrhoea in this study were identified as ST26, which is also the predominant ST of S. Thompson in human-, animal-and food-associated samples in previous studies [9,21,42].…”

“…This observation is in accordance with those reported from turtles in Spain (59.3 %) and from other studies in China (five provinces, 45.2 %; Shanghai, 19.4 %), but different from reports from the West Indies, where the dominant serovar is S . Montevideo [9, 12, 21, 41]. Furthermore, nearly all of the S .…”

Free-Living Aquatic Turtles as Sentinels of Salmonella spp. for Water Bodies

“…Wild turtles in the United States are often presumed to harbor a high prevalence of Salmonella because most of the published information regarding Salmonella prevalence in turtles comes from studies focused primarily on pet turtles or from epidemiological investigations following an outbreak, which often involve commercial breeding facilities (28,(67)(68)(69). Compared to studies in other countries (7,34,39,40,43,45,47,(70)(71)(72)(73), there is a paucity of information about Salmonella prevalence in wild turtles, in the United States (41, (2012)(2013). CHPIC and TRSCR were classified as baskers, while CHSER, STODO, and STMIN were classified as non-baskers.…”

Bacterial Infections in Sea Turtles

“…Both serotypes have been also reported in terrestrial and aquatic wild animals in the Caribbean islands; therefore, an epidemiological cycle between turtles and other animals could be assumed [ 60 , 61 , 62 ]. In addition, more recently, Edwards and collaborators [ 63 ], testing sea turtles on the same island, isolated S. typhimurium , S. montevideo , S. newport , and the serotypes S . I:6,7:-:- and S .…”

“…Nesting leatherback turtles had contact with the sand while foraging hard-shell turtles did not, especially male and juvenile turtles, as only mature females return to land once hatched. Therefore, the bacterial contamination of the sand could result in the transmission of S. enterica to nesting turtles who, subsequently, come ashore to nest [ 63 ].…”