Antimicrobial Resistance and Molecular Characterization of Salmonella Rissen Isolated in China During 2008-2019

Background: This study aimed to provide epidemiological features of Salmonella enterica serovar Rissen, determine antimicrobial susceptibility, virulence gene profiles, and describe the potential association of S. Rissen from different sources in China. Methods: During 2008-2019, a total of non-repetitive 228 S. Rissen isolates were collected from human, animals and environment in China. The antimicrobial susceptibility test, screening of antimicrobial and virulence genes by PCR, and pulsed -field gel electrophoresis (PFGE) were performed. Results: Among the 154 isolates from human, the majority of the cases (80.5%) occurred in summer, and S. Rissen was mainly detected in people aged 21-40 (37.7%) and 41-60 (28.6%) years old, and 74 non -human source S. Rissen strains were identified, with pork being the most common source. About 93.4% isolates were resistant to at least one of the 12 tested antimicrobial agents, and high frequencies of resistance were observed for tetracyclines (91.2%), trimethoprim-sulfamethoxazole (74.1%) and ampicillin (67.5%). A total of 171 (75%) isolates were resistant to at least three categories of antimicrobials, and the most common resistance profile was Tetracycline(s)-beta-Lactams-Sulfonamides. The resistance rates to chloramphenicol, quinolones and sulfafurazole were significantly higher in strains isolated from human compared to non -human source strains. Among these isolates, the beta-Lactams resistance was mainly associated with gene blaTEM (54.7%), sulfonamide resistance with sul2 (45.7%) and sul3 (54.3%), tetracycline resistance with tetA (81.3%). All the isolates harbored virulence genes hilA, sopB, sciN, stn and ssrB, and most of them harbored ssaQ (98.7%), mgtC (98.7%) and invA (98.2%). The majority (91.7%) of S. Rissen isolates showed high similarity (>80%) with each other in PFGE patterns and came from human, animals and environment. Conclusion: The high frequencies of multidrug resistance and probable clonal dissemination in this serovar call for the necessity of systematic surveillance on S. Rissen in China.