Cytotoxicity and Antimicrobial Resistance of Salmonella enterica Subspecies Isolated from Raised Reptiles in Beijing, China

SIMPLE SUMMARY: Reptiles are well recognized as the asymptomatic carriers of Salmonella spp., which is mainly inhabited in the gastrointestinal (GI) mucosa of reptile species. A variety of Salmonella serovars, including human-specific pathogenic strains, have been isolated from reptiles previously. In addition, with the growth of the pet reptile market in China, reptile-associated Salmonella infections have been noticed as a significant contributor to overall human salmonellosis. However, it remains unclear regarding the prevalence of reptile-associated Salmonella in China or its implications on human health. This study aims to investigate the prevalence of Salmonella in captive reptile species in the Beijing area through culturation-based identification and to characterize drug resistance as well as host cell virulence in these isolated species. Further, by assessing the overall prevalence of drug-resistant Salmonella strains in captive reptiles in Beijing, China, our results highlight the potential threat of zoonotic salmonellosis from pet reptiles in the Beijing area of China. ABSTRACT: Background: Reptiles are asymptomatic carriers of Salmonella spp. Reptile-associated Salmonella infections have been noticed as a significant contributor to overall human salmonellosis. However, it remains unclear regarding the prevalence of reptile-associated Salmonella in China. Methods: Fecal and gastrointestinal mucosal samples were taken from 104 snakes, 21 lizards, and 52 chelonians and cultured on selective medium. The positive clones were validated and annotated by biochemical screening and multiplex PCR verification. In addition, the antibiotic resistance of identified Salmonella isolates was detected and followed by cytotoxic activity detection on human colon cells via co-culturation. Results: The overall prevalence of Salmonella in reptiles was 25.99%, with rates of 30.77%, 47.62%, and 7.69% in snakes, lizards, and chelonians, respectively. Further, all isolates showed variable drug-resistant activity to 18 antibiotics, of which 14 strains (30.43%) were resistant to more than eight kinds of antibiotics. More than half of isolated Salmonella strains were more toxic to host cells than the standard strain, SL1344. Whole genome sequencing (WGS) results showed that all lizard-associated strains belong to 4 serovar types, and 7 of them fall into the highly pathogenic serovars “Carmel” and “Pomona.” Conclusions: Our results highlight the potential threat of zoonotic salmonellosis from captive reptiles in the Beijing area of China.