Etiological analysis of Yersinia pestis in Dulan County, Qinghai Province / 中国热带医学

ABSTRACT

@#Abstract Objective　To understand the epidemic characteristics of plague and the phenotypic characteristics of Yersinia pestis strains strains in Dulan County, Qinghai Province, so as to provide theoretical reference for timely adjustment of the local plague surveillance program and prevention of plague recurrence, as well as effective experimental basis for clinical treatment and prevention. Methods　The biochemical characteristics, virulence factor identification and plasmid analysis of 23 Yersinia pestis strains isolated from Dulan County, Qinghai Province from 1964 to 1994 were studied by conventional methods and molecular biology techniques. At the same time, the different region (DFR) method was applied to study the genetic typing of 23 Yersinia pestis strains isolated from Dulan County, Qinghai Province according to 23 different regions of plague genome and the designed primers based on PMT1. Results　Among the 23 Y. pestis strains isolated from Dulan County, 22 strains of Y. pestis were palaeotypic biotypes, and biochemical types were Qinghai-Tibet Plateau type, and 1 strain was incompatible with both biotypes and biochemical types in this area. And 86.96% (20/23) of Y. pestis strains had four virulence factors (F1+, Pst I+, VW+, Pgm+). All of the tested strains produced F1 and Pst I, while 95.65% (22/23) of tested strains were positive for VW, and 86.96% were Pgm positive. All the 23 strains carried three plasmids, with a relative molecular weight (Mr) of 6×106, 45×106, 52×106, and these plasmids formed a stable plasmid spectrum 6×106, 45×106, 52 ×106. The DFR typing results showed that Yersinia pestis could be divided into two genotypes, namely G05 and G08. Nineteen Yersinia pestis strains were G08 and four strains were G05. Conclusions　The 23 strains of Yersinia pestis isolated from Dulan County were mostly of Qinghai-Tibet Plateau type, and had stable biochemical characteristics. The virulence of Yersinia pestis was strong. The results of plasmid analysis and genotyping showed that the Yersinia pestis had the etiological characteristics of Qinghai-Tibet Plateau, which was consistent with the characteristics of Marmota himalayana plague foci in Qinghai-Tibet Plateau.