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Salmonella Enteritidis emerged as a major egg-associated pathogen in the late 20th century. Epidemiologic data from England, Wales, and the United States indicate that S. Enteritidis filled the ecologic niche vacated by eradication of S. Gallinarum from poultry, leading to an epidemic increase in human infections. We tested this hypothesis by retrospective analysis of epidemiologic surveys in Germany and demonstrated that the number of human S. Enteritidis cases is inversely related to the prevalence of S. Gallinarum in poultry. Mathematical models combining epidemiology with population biology suggest that S. Gallinarum competitively excluded S. Enteritidis from poultry flocks early in the 20th century.

Salmonella enterica serovar Typhimurium definitive type 2 (DT2) is host restricted to Columba livia (rock or feral pigeon) but is also closely related to S. Typhimurium isolates that circulate in livestock and cause a zoonosis characterized by gastroenteritis in humans. DT2 isolates formed a distinct phylogenetic cluster within S. Typhimurium based on whole-genome-sequence polymorphisms. Comparative genome analysis of DT2 94-213 and S. Typhimurium SL1344, DT104, and D23580 identified few differences in gene content with the exception of variations within prophages. However, DT2 94-213 harbored 22 pseudogenes that were intact in other closely related S. Typhimurium strains. We report a novel in silico approach to identify single amino acid substitutions in proteins that have a high probability of a functional impact. One polymorphism identified using this method, a single-residue deletion in the Tar protein, abrogated chemotaxis to aspartate in vitro. DT2 94-213 also exhibited an altered transcriptional profile in response to culture at 42°C compared to that of SL1344. Such differentially regulated genes included a number involved in flagellum biosynthesis and motility. IMPORTANCE Whereas Salmonella enterica serovar Typhimurium can infect a wide range of animal species, some variants within this serovar exhibit a more limited host range and altered disease potential. Phylogenetic analysis based on whole-genome sequences can identify lineages associated with specific virulence traits, including host adaptation. This study represents one of the first to link pathogen-specific genetic signatures, including coding capacity, genome degradation, and transcriptional responses to host adaptation within a Salmonella serovar. We performed comparative genome analysis of reference and pigeon-adapted definitive type 2 (DT2) S. Typhimurium isolates alongside phenotypic and transcriptome analyses, to identify genetic signatures linked to host adaptation within the DT2 lineage.

Aim: The number of pet reptiles is steadily increasing. Reptiles are known to shed Salmonella frequently. These salmonella are pathogenic to humans and reptile-associated salmonellosis is being recognised as an emerging zoonosis. In the present study a review of the current scientific literature was carried out, to estimate the extent of the occurrence, the risk, and the prophylactic measures against reptile-associated salmonellosis. The knowledge about the management of Salmonella, in reptiles is of importance both for veterinarians in private practice and for local veterinary authorities. Furthermore, the information and education of the reptile owners about the danger of infection could reduce the incidence of reptile-associated salmonellosis. Material and methods: Literature review and retrospective analysis of own data. Results: Up to 90% of captive reptiles excrete Salmonella often without clinical signs in contrast to free-ranging and wild reptiles, which appear to rarely shed Salmonella. Reptile-associated salmonellosis in humans are frequently caused by the serovars of the subspecies I, II, and especially by the subspecies IIIb and IV. Children have the highest risk of infection. The information about that danger of infection of reptile owners could represent an effective prophylactic measure to reduce the incidence of reptile-associated salmonellosis. Conclusions and clinical relevance: Reptile-associated salmonellosis represents a important zoonosis. The increasing number of reptiles as patients in private veterinary practice request veterinarians to acquire a basic knowledge on the importance of hygienic handling of reptiles. In addition veterinarians play an important role to provide scientifically-based information about the risk of reptile-associated salmonellosis for owners. Important measures to exclude reptile-associated salmonellosis are to avoid contact of reptiles or their excrements with small children (< 5 years) and food intended for human co