Far East scarlet-like fever (FESLF) is a serious disease caused by Yersinia pseudotuberculosis. FESLF was firstly described at the Far-East region of Russia at the end of 1950s (1). Since that time it was registered predominantly at this and closely situated regions including Japan and China. FESLF is caused by a few Y. pseudotuberculosis genotypes belonging to serovars O1b and O3 (2). Our work was aimed to reveal features characteristic for FESLF causative agents.
86 Y. pseudotuberculosis strains including 41 strains isolated from FESLF patients were included in the study. Strains were characterized with MLST. Variability of invasion factors invasin and YadA, and Rho-modifying toxins YopE and Cnf was analyzed by gene sequencing. Gene diversity and positive selection tests were performed with DnaSP and Mega6 software.
All strains isolated from FESLF patients carried the same alleles of inv, yopE and cnf genes despite the strains belonged to different serovars and clones according to MLST typing. Comparison with strains isolated from other sources and analysis of gene diversity demonstrated that a noticeable feature of Y. pseudotuberculosis virulence genes was the predominance of nonsynonymous substitutions, whereas basic parameters of nucleotide diversity were similar in virulence and housekeeping genes. Positive selection was confirmed for yopE by the Tajima neutrality test.
Obtained results suggested that FESLF symptomatology is caused by strains carrying specific virulence traits. These traits might be important markers to reveal potential FESLF causing agents that belong to undescribed clones.