Characteristics of salmonellosis pathogens circulating in Primorsky Krai before and during the COVID-19 pandemic

Introduction. To date, among intestinal infections, salmonellosis is a pressing health problem worldwide, including in the Russian Federation, causing acute infectious outbreaks of disease. Objective of the study: to assess the impact of the COVID-19 pandemic on the epidemiological patterns and molecular biological characteristics of salmonella infection in Primorsky Krai for 2019–2023. Materials and methods. A retrospective epidemiological analysis of salmonellosis incidence during the COVID-19 pandemic in the population of Primorsky Krai was conducted. Plasmid characteristics of non-typhoidal Salmonella strains and their serotype were established using alkaline lysis and serological typing methods. Results. During the COVID-19 pandemic, both in the Russian Federation and in Primorsky Krai, the registration of salmonellosis was significantly lower than in the pre-pandemic period, and the seasonality of salmonellosis shifted to the autumn months. An inverse relationship of medium strength was revealed between the monthly incidence of salmonellosis and COVID-19. No significant changes in the plasmid spectrum and in the proportion of registration by serogroups and serotypes of Salmonella were observed. It was shown that salmonellosis infection in Primorsky Krai is mainly caused by S. enteritidis strains with a plasmid characteristic of 38 MDa, 38:1.4 MDa, 38:2.3 MDa, 38:4.4 MDa, rare variants of plasmid types were also detected, the influence of the COVID-19 pandemic on the emergence of new plasmid types has not been established. Conclusion. The presented results of the study on the molecular biological characteristics of Salmonella circulating in Primorsky Krai during the COVID-19 pandemic will open up prospects for understanding the ecological and epidemiological patterns of the development of the epidemic process of salmonella infection.