ABSTRACT
Objective To study the biological characteristics and epidemiological significance of Yersinia pestis in Chengduo County of Qinghai Province,in order to provide scientific basis for plague prevention and control in this area.Methods Thirty one strains of Yersinia pestis isolated from Chengduo County of Qinghai Province from 1980 to 2011 were selected as study subjects.Biochemical test,virulence factors evaluation [Fra1 (F1),pesticin Ⅱ (Pst Ⅱ),virulence antigen (VW),pigmentation (Pgm)] and different region (DFR) genotyping were carried out.Nineteen of the 31 strains Yersinia pestis were selected according to different time,different areas and different hosts to determine their toxicity in mice,MLD ≤ 10 000 was strong toxic strain,10 000 ＜ MLD ＜ 100 000 was moderate toxic strain.Results Among thirty one strains of Yersinia pestis,23 strains were isolated from human,the Himalaya marmot and its fleas and lice,and their biological type was classical,biochemical type was Qinghai-Tibet plateau;21 strains genotype was type 5,1 was type 16,1 was type 32,and they contained all four kinds of virulence factors (F1,Pgm,Pst Ⅱ,VW),and toxicity test showed all strains (14) were strong toxic strains.The rest 8 strains of Yersinia pestis isolated from the Microtus fuscus and its fleas,and their biological type was Microtus,biochemical type was Chuanqing plateau;they could produce F1 and Pgm,of which 87.5％ (7/8) strains could produce Pst Ⅱ,but could not produce VW antigen factor,the genotype was 14,and the toxicity results showed that they were strong (3)and moderate (2) toxic strains.Conclusion The strains separated in Chengduo County of Qinghai Province from 1980 to 2011 have the pathogen characteristics of Qinghai-Tibet plateau plague,they are mainly strong toxic strains;the work on prevention and control of plague should not be neglected.