From Bacterial Diversity to Zoonotic Risk: Characterization of Snake-Associated Salmonella Isolated in Poland with a Focus on Rare O-Ag of LPS, Antimicrobial Resistance and Survival in Human Serum.

The One Health approach emphasizes the importance of zoonoses due to their pandemic potential, highlighting the need to characterize emerging bacterial pathogens across animal reservoirs. Non-typhoidal Salmonella (NTS) species are among the most common zoonotic agents and can be transmitted by various reservoirs, including reptiles. Both direct and indirect contact with reptiles may result in Reptile-Associated Salmonellosis (RAS), which mainly affects children, immunocompromised individuals, pregnant women, and the elderly. This study aimed to isolate and characterize the Gram-negative intestinal microbiota from free-living snakes in Poland (Natrix natrix, Natrix tessellata, Coronella austriaca, Zamenis longissimus, and Elaphe dione) and to determine the prevalence and virulence potential of Salmonella. Using MALDI-TOF Mass Spectrometry, 432 isolates were identified. Serological analysis of 62 Salmonella isolates revealed 10 distinct O-antigen groups, and rare serovars O:38, O:48, O:57 and others were confirmed. Salmonella isolates were tested for antibiotic susceptibility and resistance to Human Serum; most isolates survived exposure to serum while remaining susceptible to antibiotics. One isolate was classified as multidrug-resistant (MDR), showing resistance to amoxicillin/clavulanic acid, ampicillin, cefuroxime, cephalexin, tigecycline, and fosfomycin. These findings demonstrate that wild snakes in Poland can act as reservoirs of pathogenic and zoonotic Salmonella, emphasizing their epidemiological significance in natural ecosystems.