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

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

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

RESULTS: 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.

CONCLUSION: 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.