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In the United States (U.S.), pet turtles have been associated with outbreaks of salmonellosis, a serious and sometimes-fatal intestinal illness caused by Salmonella bacteria, with nearly 300,000 people being infected in some years. Children are particularly susceptible because of their propensity to put items, including small turtles, in their mouths. In 1975, a U.S. federal regulation prohibited the sale of turtles <4 inches (101.6 mm) in size, except for the purposes of export, scientific, or educational purposes. This regulation was established to reduce the incidence of salmonellosis, particularly in small children. Previous research has not evaluated the availability of turtles <4 inches in size on websites selling wildlife. We monitored 16 websites in 2021 and quantified listings of small turtles. We determined whether information on Salmonella, the 1975 federal regulation, or related state regulations were provided on the websites and determined legality of sales of small turtles by state regulations. We found that all 16 websites openly advertised and sold turtles <4 inches in size, but only half of these websites provided information about Salmonella and/or the federal regulation. These websites required buyers to confirm that they were not purchasing a turtle as a pet, thereby putting the onus on the consumer to adhere to the regulation. We documented 515 listings of turtles <4 inches in size, including 47 species and one hybrid. Our study has demonstrated that internet sales of small turtles currently represent part of the thriving online pet trade in the U.S. Enforcement of the federal regulation faces jurisdictional challenges in most states. Therefore, we recommend continued public education campaigns by public health agencies in the U.S. to help reduce the risk that pet turtle ownership presents., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2022 Montague et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Microbes have central roles in the development and health of animals, being the introduction of specific microbial species a potential conservation strategy to protect animals from emerging diseases. Thus, insight into the microbiota of the species and their habitats is essential. In this manuscript, we report for the first time the bacterial composition of all the components (eggshells of hatched and unhatched eggs, internal content of unhatched eggs, intestinal content of hatchling and pipping sea turtles, and sand) of three nesting beaches of Caretta caretta along the Italian coasts of the Mediterranean Sea. The analysis of 26 amplicon samples was carried out using next-generation sequencing analysis, targeting V3-V4 regions of the bacterial 16S rRNA gene. Samples featured mainly Proteobacteria, Actinobacteria, Firmicutes, and Bacteroidetes, whose percentages depended on the sample type. Our results showed that, although from different sampling sites, the internal content of the unhatched eggs, intestinal content of hatchling and pipping sea turtles share the microbiota, which was yet different from that of eggshells and sand of the same nesting beach. This study suggests the maternal and environmental influence alongside a protective role of eggshells in shaping the egg microbiota of Caretta caretta sea turtles., Competing Interests: The authors have declared that no competing interests exist.

Microbial communities of animals play a role in health and disease, including immunocompromised conditions. In the northeastern United States, cold-stunning events often cause endangered Kemp's ridley turtles (Lepidochelys kempii) to become stranded on beaches in autumn. These sea turtles are admitted to rehabilitation facilities when rescued alive and are presumed immunocompromised secondary to hypothermia. To better understand the role that microbes play in the health of cold-stunned sea turtles, we characterized the oral and cloacal microbiome from Kemp's ridley turtles at multiple timepoints during rehabilitation, from admission to pre-release, by using Illumina sequencing to analyze the 16S rRNA gene. Microbial communities were distinct between body sites and among turtles that survived and those that died. We found that clinical parameters such as presence of pneumonia or values for various blood analytes did not correlate with oral or cloacal microbial community composition. We also investigated the effect of antibiotics on the microbiome during rehabilitation and prior to release and found that the type of antibiotic altered the microbial community composition, yet overall taxonomic diversity remained the same. The microbiome of cold-stunned Kemp's ridley turtles gradually changed through the course of rehabilitation with environment, antibiotics, and disease status all playing a role in those changes and ultimately the release status of the turtles., Competing Interests: The authors have declared that no competing interests exist.

Microbial communities associated with freshwater aquatic habitats and resident species are both critical to and indicative of ecosystem status and organismal health. External surfaces of turtle shells readily accumulate microbial growth and could carry representation of habitat-wide microbial diversity, since they are in regular contact with multiple elements of freshwater environments. Yet, microbial diversity residing on freshwater turtle shells is poorly understood. We applied 16S and 18S metabarcoding to characterize microbiota associated with external shell surfaces of 20 red-eared slider (Trachemys scripta) turtles collected from varied habitats in central and western Oklahoma, and ranging to southeast Iowa. Shell-associated microbial communities were highly diverse, with samples dominated by Bacteroidia and alpha-/gamma-proteobacteria, and ciliophoran alveolates. Alpha diversity was lower on turtle shells compared to shallow-water-associated environmental samples, likely resulting from basking-drying behavior and seasonal scute shedding, while alpha diversity was higher on carapace than plastron surfaces. Beta diversity of turtle shells was similarly differentiated from environmental samples, although sampling site was consistently a significant factor. Deinococcus-Thermus bacteria and ciliophoran alveolates were recovered with significantly higher abundance on turtle shells versus environmental samples, while bacterial taxa known to include human-pathogenic species were variably more abundant between shell and environmental samples. Microbial communities from a single, shared-site collection of the ecologically similar river cooter (P. concinna) largely overlapped with those of T. scripta. These data add to a foundation for further characterization of turtle shell microbial communities across species and habitats, with implications for freshwater habitat assessment, microbial ecology and wildlife conservation efforts., Competing Interests: The authors have declared that no competing interests exist.

The aim of the study was to detect and genetically characterize Arcobacter butzleri in pet red-footed tortoises suspected for Campylobacter spp., using molecular techniques. A written consent from tortoise owners was obtained, after explaining the advantages of the research to tortoise owners of Grenada. Fecal samples were collected from 114 tortoises from five parishes of the country and cultured for Campylobacter spp. using selective culture techniques. A. butzleri was isolated from 4.39% of pet tortoises. Total thirteen isolates were obtained; all identified as A. butzleri by a universal and a species-specific Polymerase Chain Reaction (PCR) and direct sequencing. Genetic characterization of these isolates was performed based on Enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) that generated eight different genetic fingerprints with a discriminatory power of 0.91. Campylobacter species were not detected molecularly in any of the culture-positive samples. This is the first report of infection of pet tortoises in Grenada, West Indies with A. butzleri. This study emphasizes on the risk of zoonotic transmission of A. butzleri by exotic pets, which is a serious concern for public health., Competing Interests: The authors have declared that no competing interests exist.

Threatened and endangered green turtles (Chelonia mydas) are unique because as juveniles they recruit from pelagic to near-shore waters and shift from an omnivorous to primarily herbivorous diet (i.e. seagrass and algae). Nevertheless, when injured and ill animals are admitted to rehabilitation, animal protein (e.g. seafood) is often offered to combat poor appetite and emaciation. We examined how the fecal microbiome of juvenile green turtles changed in response to a dietary shift during rehabilitation. We collected fecal samples from January 2014 -January 2016 from turtles (N = 17) in rehabilitation at the Georgia Sea Turtle Center and used next generation sequencing to analyze bacterial community composition. Samples were collected at admission, mid-rehabilitation, and recovery, which entailed a shift from a mixed seafood-vegetable diet at admission to a primarily herbivorous diet at recovery. The dominant phyla changed over time, from primarily Firmicutes (55.0%) with less Bacteroidetes (11.4%) at admission, to primarily Bacteroidetes (38.4%) and less Firmicutes (31.8%) at recovery. While the microbiome likely shifts with the changing health status of individuals, this consistent inversion of Bacteroidetes and Firmicutes among individuals likely reflects the increased need for protein digestion, for which Bacteroidetes are important. Firmicutes are significant in metabolizing plant polysaccharides; thus, fewer Firmicutes may result in underutilization of wild diet items in released individuals. This study demonstrates the importance of transitioning rehabilitating green turtles to an herbivorous diet as soon as possible to afford them the best probability of survival., Competing Interests: Funding for this research was provided by The Coca Cola Company. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Caretta caretta is the most common sea turtle species in the Mediterranean Sea. The species is threatened by anthropomorphic activity that causes thousands of deaths and hundreds of strandings along the Mediterranean coast. Stranded turtles are often cared for in rehabilitation centres until they recover or die. The objective of this study was to characterize the gut microbiome of nine sea turtles stranded along the Sicilian coast of the Mediterranean Sea using high-throughput sequencing analysis targeting V3-V4 regions of the bacterial 16S rRNA gene. Stool samples were collected from eight specimens hosted in the recovery centre after a few days of hospitalization (under 7) and from one hosted for many weeks (78 days). To better explore the role of bacterial communities in loggerhead sea turtles, we compared our data with published fecal microbiomes from specimens stranded along the Tuscan and Ligurian coast. Our results highlight that, despite the different origin, size and health conditions of the animals, Firmicutes, Bacteroidetes and Proteobacteria constitute the main components of the microbiota. This study widens our knowledge on the gut microbiome of sea turtles and could be helpful for the set up of rehabilitation therapies of stranded animals after recovery in specialized centres., Competing Interests: The authors have declared that no competing interests exist.

Leptospira spp. are re-emerging zoonotic pathogens. Previous research has found that Blanding's turtles (Emydoidea blandingii) experimentally infected with Leptospira interrogans shed leptospires in their urine, suggesting that they could play a role in transmitting pathogen within an aquatic ecosystem. This study investigated whether a population of wild Blanding's turtles known to be exposed to Leptospira spp. actively shed the pathogen under natural conditions. Blood samples were collected for serologic testing and to assess the health of the turtles. Free catch urine was collected for polymerase chain reaction (PCR) testing. All turtles were seropositive for Leptospira spp. and 73.5% (25/34) of the urine samples were PCR positive. All animals appeared clinically healthy and showed no apparent signs of disease. This study confirms that wild Blanding's turtles can actively shed Leptospira spp. in their urine and suggests that they may play a role in the epidemiology of this disease in habitats in which they reside., Competing Interests: Funding for this study was received from Fluker Farms and Abaxis Inc. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Upper respiratory tract disease (URTD) in North American tortoises (Gopherus) has been the focus of numerous laboratory and field investigations, yet the prevalence and importance of this disease remains unclear across many tortoise populations. Furthermore, much research has been focused on understanding diagnostic biomarkers of two known agents of URTD, Mycoplasma agassizii and Mycoplasma testudineum, yet the reliability and importance of these diagnostic biomarkers across populations is unclear. Gopher Tortoises (Gopherus polyphemus) have experienced significant declines and are currently protected range wide. Geographically, Alabama represents an important connection for Gopher Tortoise populations between the core and periphery of this species' distribution. Herein, we systematically sampled 197 Gopher Tortoises for URTD across seven sites in south-central and south-eastern Alabama. Plasma samples were assayed for antibodies to M. agassizii and M. testudineum; nasal lavage samples were assayed for the presence of viable pathogens as well as pathogen DNA. Lastly, animals were scored for the presence of external symptoms and nasal scarring consistent with URTD. External symptoms of URTD were present in G. polyphemus in all sites sampled in Alabama. There was no relationship between active symptoms of URTD and Mycoplasma antibodies, however the presence of URTD nasal scarring was positively related to M. agassizii antibodies (P = 0.032). For a single site that was sampled in three sequential years, seroprevalence to M. agassizii significantly varied among years (P < 0.0001). Mycoplasma agassizii DNA was isolated from four of the seven sites using quantitative PCR, yet none of the samples were culture positive for either of the pathogens. An analysis of disease status and condition indicated that there was a significant, positive relationship between the severity of URTD symptoms and relative body mass (P < 0.05). This study highlights the need for continued monitoring of disease in wild populations. Specifically, focus must be placed on identifying other likely pathogens and relevant biomarkers that may be important drivers of URTD in North American tortoises. Special consideration should be given to environmental contexts that may render wild populations more susceptible to disease., Competing Interests: The authors have declared that no competing interests exist.

Sea turtles are distributed in tropical and subtropical seas worldwide. They play several ecological roles and are considered important indicators of the health of marine ecosystems. Studying epibiotic diatoms living on turtle shells suggestively has great potential in the study of turtle behavior because diatoms are always there. However, diatom identification at the species level is time consuming, requires well-trained specialists, and there is a high probability of finding new taxa growing on turtle shells, which makes identification tricky. An alternative approach based on DNA barcoding and high throughput sequencing (HTS), metabarcoding, has been developed in recent years to identify species at the community level by using a DNA reference library. The suitabilities of morphological and molecular approaches were compared. Diatom assemblages were sampled from seven juvenile green turtles (Chelonia mydas) from Mayotte Island, France. The structures of the epibiotic diatom assemblages differed between both approaches. This resulted in different clustering of the turtles based on their diatom communities. Metabarcoding allowed better discrimination between turtles based on their epibiotic diatom assemblages and put into evidence the presence of a cryptic diatom diversity. Microscopy, for its part, provided more ecological information of sea turtles based on historical bibliographical data and the abundances of ecological guilds of the diatom species present in the samples. This study shows the complementary nature of these two methods for studying turtle behavior.

A variety of Chlamydia species belonging to the Chlamydiaceae family have been reported in reptilian hosts but scarce data about their occurrence in turtles and tortoises are available. In this study, research was conducted to acquire information on invasive alien species (IAS) of turtles and indigenous turtles and tortoises, living both free and in captivity, as possible reservoirs of Chlamydiaceae. Analysis of specimens (pharyngeal and cloacal swabs and tissues) from 204 turtles and tortoises revealed an overall Chlamydiaceae prevalence of 18.3% and 28.6% among free-living and captive animals respectively, with variable levels of shedding. Further testing conducted with a species-specific real-time PCR and microarray test was unsuccessful. Subsequently sequencing was applied to genotype the Chlamydiaceae-positive samples. Almost the full lengths of the 16S rRNA and ompA genes as well as the 16S-23S intergenic spacer (IGS) and 23S rRNA domain I were obtained for 14, 20 and 8 specimens respectively. Phylogenetic analysis of 16S rRNA amplicons revealed two distinct branches. Group 1 (10 specimens), specific to freshwater turtles and reported here for the first time, was most closely related to Chlamydia (C.) pneumoniae strains and the newly described Candidatus C. sanzinia. Group 2 (four specimens), detected in Testudo spp. samples, showed highest homology to C. pecorum strains but formed a separate sub-branch. Finally, molecular analysis conducted on positive samples together with their geographical distribution in places distant from each other strongly suggest that Group 1 specimens correspond to a new species in the Chlamydiaceae family. In-depth studies of Chlamydia spp. from turtles and tortoises are needed to further characterise these atypical strains and address arising questions about their pathogenicity and zoonotic potential.

The gut microbiome of herbivorous animals consists of organisms that efficiently digest the structural carbohydrates of ingested plant material. Green turtles (Chelonia mydas) provide an interesting model of change in these microbial communities because they undergo a pronounced shift from a surface-pelagic distribution and omnivorous diet to a neritic distribution and herbivorous diet. As an alternative to direct sampling of the gut, we investigated the cloacal microbiomes of juvenile green turtles before and after recruitment to neritic waters to observe any changes in their microbial community structure. Cloacal swabs were taken from individual turtles for analysis of the 16S rRNA gene sequences using Illumina sequencing. One fecal sample was also obtained, allowing for a preliminary comparison with the bacterial community of the cloaca. We found significant variation in the juvenile green turtle bacterial communities between pelagic and neritic habitats, suggesting that environmental and dietary factors support different bacterial communities in green turtles from these habitats. This is the first study to characterize the cloacal microbiome of green turtles in the context of their ontogenetic shifts, which could provide valuable insight into the origins of their gut bacteria and how the microbial community supports their shift to herbivory.

Filamentous algae are often visible on the carapaces of freshwater turtles and these algae are dominated by a few species with varying geographic distributions. Compared to filamentous algae, little is known about the much more speciose microalgae on turtles. Our objectives were to compare the diatom flora on a single turtle species (the common snapping turtle, Chelydra serpentina) across part of its range to examine spatial patterns and determine whether specific diatom taxa were consistently associated with turtles (as occurs in the filamentous alga Basicladia spp.). Using preserved turtle specimens from museums, we systematically sampled diatoms on the carapaces of 25 snapping turtles across five states. The diverse diatom assemblages formed two groups-the southern Oklahoma group and the northern Illinois/Wisconsin/New York group, with Arkansas not differing from either group. Of the six diatom species found in all five states, four species are widespread, whereas Luticola cf. goeppertiana and L. cf. mutica are undescribed species, known only from turtles in our study. L. cf. goeppertiana comprised 83% of the diatom abundance on Oklahoma turtles and was relatively more abundant on southern turtles (Oklahoma and Arkansas) than on northern turtles (where mean abundance/state was > 10%). L. cf. mutica was the most abundant species (40%) on New York turtles. Some Luticola species are apparently turtle associates and results support a pattern of spatial variation in Luticola species, similar to that in Basicladia. Using museum specimens is an efficient and effective method to study the distribution of micro-epibionts., Competing Interests: The authors have declared that no competing interests exist.

The macro-epibiotic communities of sea turtles have been subject to growing interest in recent years, yet their micro-epibiotic counterparts are almost entirely unknown. Here, we provide the first evidence that diatoms are epibionts for all seven extant species of sea turtle. Using Scanning Electron Microscopy, we inspected superficial carapace or skin samples from a single representative of each turtle species. We distinguished 18 diatom taxa from these seven individuals, with each sea turtle species hosting at least two diatom taxa. We recommend that future research is undertaken to confirm whether diatom communities vary between sea turtle species and whether these diatom taxa are facultative or obligate commensals.

Probiotics are widely used in nutrition, and their mode of action is intensively studied in mammals and birds; however, it is almost unknown in reptiles. In the present study, Trachemys scripta scripta and Sternotherus odoratus were used to assess the effects of dietary probiotics on chelonian gastrointestinal tract microecology. In the first, 20-week experiment, 40 young T. s. scripta were randomly distributed to four experimental groups: 1st, (CON)--with no additives; 2nd, (SSPA) with Bacillus subtilis PB6; 3rd, (MSP)--with multiple strain probiotic; and 4th, (SSPB) with Bacillus subtilis C-3102. The first study has shown that SSPA and MSP decreased the numbers of total bacteria, Enterobacteriace, Staphylococcus sp. and Streptococcus sp. excreted to water and increased the villous height and mucosa thickness in duodenum. SSPB improved the duodenal microstructure; however, it also increased numbers of kanamycin and vancomycin resistant bacteria, Staphylococcus sp. and Streptococcus sp., in water. In the second, 52-week experiment, 30 S. odoratus were randomly assigned to three dietary treatments. CON, SSPA and MSP groups. The MSP preparation increased the body weight gain, crude ash, Ca and P share in the turtles' shells. Both probiotics affected duodenal histomorphology. SSPA decreased the villous height, while MSP increased the villous height and mucosa thickness, and decreased the crypt depth. SSPA decreased the concentrations of bacteria excreted to water. In the case of intestinal microbiota, bacteria suppressing effects were observed in the case of both probiotics. MSP increased the number of Bifidobacterium sp. and Lactobacillus sp./Enteroccoccus sp., and decreased the number of Clostridium perfringens and Campylobacter sp. in the small intestine. In the large intestine it lowered, amongst others, Bacteroides-Pervotella cluster, Clostridium leptum subgroup and Clostridium perfringens numbers. The above-mentioned results suggest that probiotics are useful in turtle nutrition due to their positive effects on growth performance, shell mineralization, duodenal histomorphology and microbiota.

Habitat bioaugmentation and introduction of protective microbiota have been proposed as potential conservation strategies to rescue endangered mammals and amphibians from emerging diseases. For both strategies, insight into the microbiomes of the endangered species and their habitats is essential. Here, we sampled nests of the endangered sea turtle species Eretmochelys imbricata that were infected with the fungal pathogen Fusarium falciforme. Metagenomic analysis of the bacterial communities associated with the shells of the sea turtle eggs revealed approximately 16,664 operational taxonomic units, with Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes as the most dominant phyla. Subsequent isolation of Actinobacteria from the eggshells led to the identification of several genera (Streptomyces, Amycolaptosis, Micromomospora Plantactinospora and Solwaraspora) that inhibit hyphal growth of the pathogen F. falciforme. These bacterial genera constitute a first set of microbial indicators to evaluate the potential role of microbiota in conservation of endangered sea turtle species.

Vacuolar myelinopathy (VM) is a neurologic disease primarily found in birds that occurs when wildlife ingest submerged aquatic vegetation colonized by an uncharacterized toxin-producing cyanobacterium (hereafter "UCB" for "uncharacterized cyanobacterium"). Turtles are among the closest extant relatives of birds and many species directly and/or indirectly consume aquatic vegetation. However, it is unknown whether turtles can develop VM. We conducted a feeding trial to determine whether painted turtles (Chrysemys picta) would develop VM after feeding on Hydrilla (Hydrilla verticillata), colonized by the UCB (Hydrilla is the most common "host" of UCB). We hypothesized turtles fed Hydrilla colonized by the UCB would exhibit neurologic impairment and vacuolation of nervous tissues, whereas turtles fed Hydrilla free of the UCB would not. The ability of Hydrilla colonized by the UCB to cause VM (hereafter, "toxicity") was verified by feeding it to domestic chickens (Gallus gallus domesticus) or necropsy of field collected American coots (Fulica americana) captured at the site of Hydrilla collections. We randomly assigned ten wild-caught turtles into toxic or non-toxic Hydrilla feeding groups and delivered the diets for up to 97 days. Between days 82 and 89, all turtles fed toxic Hydrilla displayed physical and/or neurologic impairment. Histologic examination of the brain and spinal cord revealed vacuolations in all treatment turtles. None of the control turtles exhibited neurologic impairment or had detectable brain or spinal cord vacuolations. This is the first evidence that freshwater turtles can become neurologically impaired and develop vacuolations after consuming toxic Hydrilla colonized with the UCB. The southeastern United States, where outbreaks of VM occur regularly and where vegetation colonized by the UCB is common, is also a global hotspot of freshwater turtle diversity. Our results suggest that further investigations into the effect of the putative UCB toxin on wild turtles in situ are warranted.

Nascent fungal infections are currently considered as one of the main threats for biodiversity and ecosystem health, and have driven several animal species into critical risk of extinction. Sea turtles are one of the most endangered groups of animals and only seven species have survived to date. Here, we described two pathogenic species, i.e., Fusarium falciforme and Fusarium keratoplasticum, that are globally distributed in major turtle nesting areas for six sea turtle species and that are implicated in low hatch success. These two fungi possess key biological features that are similar to emerging pathogens leading to host extinction, e.g., high virulence, and a broad host range style of life. Their optimal growth temperature overlap with the optimal incubation temperature for eggs, and they are able to kill up to 90% of the embryos. Environmental forcing, e.g., tidal inundation and clay/silt content of nests, were correlated to disease development. Thus, these Fusarium species constitute a major threat to sea turtle nests, especially to those experiencing environmental stressors. These findings have serious implications for the survival of endangered sea turtle populations and the success of conservation programs worldwide.

Different studies have reported the prevalence of Salmonella in turtles and its role in reptile-associated salmonellosis in humans, but there is a lack of scientific literature related with the epidemiology of Campylobacter in turtles. The aim of this study was to evaluate the prevalence of Campylobacter and Salmonella in free-living native (Emys orbicularis, n=83) and exotic (Trachemysscripta elegans, n=117) turtles from 11 natural ponds in Eastern Spain. In addition, different types of samples (cloacal swabs, intestinal content and water from Turtle containers) were compared. Regardless of the turtle species, natural ponds where individuals were captured and the type of sample taken, Campylobacter was not detected. Salmonella was isolated in similar proportions in native (8.0 ± 3.1%) and exotic (15.0 ± 3.3%) turtles (p=0.189). The prevalence of Salmonella positive turtles was associated with the natural ponds where animals were captured. Captured turtles from 8 of the 11 natural ponds were positive, ranged between 3.0 ± 3.1% and 60.0 ± 11.0%. Serotyping revealed 8 different serovars among four Salmonella enterica subspecies: S. enterica subsp. enterica (n = 21), S. enterica subsp. salamae (n = 2), S. enterica subsp. diarizonae (n = 3), and S. enterica subsp. houtenae (n = 1). Two serovars were predominant: S. Thompson (n=16) and S. typhimurium (n=3). In addition, there was an effect of sample type on Salmonella detection. The highest isolation of Salmonella was obtained from intestinal content samples (12.0 ± 3.0%), while lower percentages were found for water from the containers and cloacal swabs (8.0 ± 2.5% and 3.0 ± 1.5%, respectively). Our results imply that free-living turtles are a risk factor for Salmonella transmission, but do not seem to be a reservoir for Campylobacter. We therefore rule out turtles as a risk factor for human campylobacteriosis. Nevertheless, further studies should be undertaken in other countries to confirm these results.

Background: LuxR-type transcription factors are typically used by bacteria to determine the population density of their own species by detecting N-acylhomoserine lactones (AHLs). However, while Escherichia and Salmonella encode a LuxR-type AHL receptor, SdiA, they cannot synthesize AHLs. In vitro, it is known that SdiA can detect AHLs produced by other bacterial species., Methodology/principal Findings: In this report, we tested the hypothesis that SdiA detects the AHL-production of other bacterial species within the animal host. SdiA did not detect AHLs during the transit of Salmonella through the gastrointestinal tract of a guinea pig, a rabbit, a cow, 5 mice, 6 pigs, or 12 chickens. However, SdiA was activated during the transit of Salmonella through turtles. All turtles examined were colonized by the AHL-producing species Aeromonas hydrophila., Conclusions/significance: We conclude that the normal gastrointestinal microbiota of most animal species do not produce AHLs of the correct type, in an appropriate location, or in sufficient quantities to activate SdiA. However, the results obtained with turtles represent the first demonstration of SdiA activity in animals.