[Study on the pathogen of plague in Sanjiangyuan area in Qinghai province]

To study the biological characteristics of Yersinia pestis and to develop prevention and control program on plague in Sanjiangyuan areas, Qinghai province.

To identify the biologic types and molecular biological features of Y.pestis isolated in Sanjiangyuan area from 1954-2007.

Among the 411 strains of Y. pestis, 12 strains belonged to the microtus type Y. pestis with denitrification (-) and donkey-hide gelatin carbohydrate (-) and glycerine (+). 399 strains belonged to classic type Y. pestis with denitrification (+) and donkey-hide gelatin carbohydrate (+) and glycerine (+). 411 Y. pestis strains had factor F I and Pst I. Among them, VW+ strains of Y. pestis accounted for 95.13% (391/411), VW-accounted for 4.87% (20/411), Pgm(+) accounted for 80.78% (332/ 411), Pgm(+/-) accounted for 9% (37/411) and Pgm(-) accounted for 10.22% (42/411) respectively. 96.82% (213/220) of the Y. pestis strains showed strong virulence to laboratory mice while 3.18% (7/220) of the strains carried medium virulence. 90.02% of the tested Y. pestis (370/411) strains had 6 x10(6), 45 x 10(6), 65 x 10(6) plasmids. 8 types of genome were found among 80 strains of Y. pestis, with 6 of them resembling ZHOU Dongsheng' s classification. Two new genome types were found.

The Y. pestis in the Sanjiangyuan area had the characteristics of plague pathogen, identified in Qinghai-Tibet plateau. It is estimated that human beings are highly susceptible to the disease which spread fast, causing serious signs and symptoms with high death rate.