Identification of dominant serotypes of standard Salmonella strains

Objective To obtain standard strains of eight main serotypes of Salmonella and establish a process for screening standard strains according to the Technical Requirements for Evaluation of National Standard Strains of Pathogenic Microorganisms (WS/T 812—2022).

Methods Morphological observation, biochemical testing, and genome sequencing analysis were conducted on 24 strains of initial and passaged Salmonella to obtain standard strains with typical morphology and biochemistry, and stable genomic characteristics.

Results The results showed that 8 strains belonging to 8 serotypes (S. Typhi, S. Paratyphi A, S. Paratyphi B, S. Paratyphi C, S. Typhimurium, S. Enteritidis, monophasic S. Typhimurium, and S. Choleraesuis) were selected from 24 Salmonella strains. These 8 strains had typical morphology and biochemical reactions on the recommended selective culture medium for Salmonella isolation, with minimal genomic variation after passage, and stable serum agglutination results, which can be used as reference strains for Salmonella testing.

Conclusion This study obtained 8 main serotype standard strains of Salmonella with corresponding pathogenic characteristics through screening, which can serve as reference strains for Salmonella detection, serotyping quality control, and genome evolution analysis, thus provide a foundation for subsequently development of nucleic acid standard materials.