Test results of virulence factor of Yersinia pestis isolated from various natural foci in China

Abstract

Objective To study the characteristics of virulence factors ofYersinia pestis (Y. pestis) isolated from different natural plague foci in China and to provide a basis for developing prevention and control measures on plague. Methods Conventional technologies were applied to examine the characteristics of four virulence factors[Fra1 (F1), Pesticin1 (PstⅠ), Virulence antigen (VW) and Pigmentation (Pgm)] of 2 212 strains of Y. pestis isolated from various host and media in different kinds natural foci since the 1950s, and chi-square test was used to contrast composition of virulence factors of Y. pestis from 11 different kinds of plague natural foci including the strains isolated from human plague patients and bodies. Results Among the 2 212 strains of Y. pestis, 72.06% (1 594/2 212) contained the four virulence factors, F1+ accounted for 99.95% (2 211/2 212), PstⅠ+ accounted for 99.64% (2 204/2 212), VW+accounted for 73.73% (1 631/2 212) , Pgm+ accounted for 72.06% (1 594/2 212), Pgm- accounted for 21.70% (480/2 212) and Pgm+/- accounted for 6.24% (138/2 212), respectively. There were no significant differences (χ2 = 0.61, 3.64, all P > 0.05)on composition of virulence factors F1 and Pst Ⅰ of Y. pestis from 11 different kinds of plague natural foci, and significant differences (χ2 = 227.99, 390.96, all P < 0.05) on composition of virulence factors VW and Pgm of Y. pestis. In addition to 4 kinds of plague natural foci where no human plague cases were found, there were significant differences (χ2 = 39.72, 51.05, all P < 0.05) on composition of VW and Pgm of Y. pestis isolated from human plague patients and bodies in other 7 different kinds of plague natural foci; all the constituent ratios of F1+ and PstⅠ+ were 100%. Conclusions Most F1 and Pst Ⅰ of Y. pestis isolated from different kinds of natural plague foci in China are in a stable state. There are significant differences in the composition of Pgm and VW of Y. pestis isolated from plague patient in China, and the strains are related to plague foci and they have biovars, ecotype and epidemiological significance. Key words: Yersinia pestis; Virulence factors; Epidemiology