Main Results of the Research on the Far Eastern Scarlet-Like Fever as a Specific Clinical and Epidemic Manifestation of Pseudotuberculosis: A Review of Comprehensive Studies

Abstract

Introduction: Until 1950s, pseudotuberculosis in humans was known in the world as a sporadic disease with appendicular syndrome. In 1959, the first outbreak of a previously unknown disease called Far Eastern scarlet-like fever (FESLF) was registered in Vladivostok. The purpose of this article is to review priority achievements of the Research Institute of Epidemiology and Microbiology named after G.P. Somov in the field of studying FESLF as a specific clinical and epidemic manifestation of pseudotuberculosis in Russia. Materials and methods: The priority data were obtained based on microbiological, epidemiological, molecular genetic, as well as pathomorphological and electron microscopic studies of biological samples from human FESLF cases and experimental animals infected with Yersinia pseudotuberculosis strains with different plasmid characteristics. Results: It has been proven that the FESLF pathogen is a specific clone of Yersinia pseudotuberculosis having a certain plasmid profile pVM82, pYV 48 MDa, sequence type (2ST) and the first allele of the yadA gene. The causative agent of FESLF is characterized by the phenomenon of psychrophilicity, which consists in its ability to multiply in the environment with its biologically low and changing temperature (4–12 °C), at which the pathogen multiplies and accumulates while preserving or increasing its virulence, thus inducing the epidemic process. The article describes the main genetic and biochemical mechanisms of Y. pseudotuberculosis adaptation to changing environmental conditions, reveals morphological manifestations of the adaptive variability of these bacteria under different conditions of their habitat, and presents the main features of the pathogenesis and morphogenesis of FESLF, including those associated with plasmid characteristics and toxigenicity of Y. pseudotuberculosis. Conclusion: Currently, the epidemic process of pseudotuberculosis/FESLF is characterized by a decrease in the proportion of outbreaks and predominance of sporadic cases. The relevance of further research is associated with the study of the dormant forms of Y. pseudotuberculosis and the formation of ideas about pseudotuberculosis as a persistent infectious disease.