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Objective Throush identify biochemical characteristics and virulence factors of 2 strains suspected Yersinia pestis(Y.pestis)isolated from the dead Marmota himalayana(M.himalayana)to confirm the nature epidemic focus in Dege County,Sichuan Province.Methods Y.pestis was analyzed by specific staining and shape,culturing characteristics,splitting-test by bacteriophage,test of biochemical characteristics and glycolysis ability,virulence factors,virulence,nutritional requirement,plasmid,genetic test and genetic type. Results The tested strains were Gram staining bacilus.The main biochemical characteristics were Arabinose(+)、 Rhamnose(-),Maltose(+),Melibiose(-),Glycerol(+),Denitrification(+).The virulence factors with FI+.VW+, Pgm+,Pst I+;and with the common 6.0×106,45.0×106,65.0×106 plasmids,also with the virulence-relative plasmid gene.Both their absolutely lethal dose(LD100)in mice were 50 bacteria.The nutritional requirement appeared which were depended on Phenylalanine and Methionine.With the Genomovar 5 genotype characteristics of M.himalayana plague foci of Qinghai-Tibet plateau.The difference between tested strains and Yersinia pseudotubercuosis on the 3 different culture medium was obvious.The tested strains had a Y.pestis' specific 3a fragment,Pst I and FI-Ag,at 22 ℃,the strains could be split by bacteriophage completely.Conclusions According to the diagnostic criteria of plague in China,the 2 suspected strains isolated from Dege County,Sichuan Province ale confirmed as Y.pestis.both with powerful virulenceand with the characteristics of the Y.pestis of M.himahtyana in Qinghai-Tibet plateau plague natural focus.
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Objective To explore the characteristics of human plague using a sero-epidemiologic method in the source of the three rivers area in Qinghai for possible plague control strategies. Methods Investigate human plague sero-epidemiologically in the source of 4 counties in the three rivers area in Qinghai. The human serum would be tested to confirm the sew-positive rate for plague F1 antibody using indirect hemagglutination assay(IHA). Results A total of 2508 local participants were tested in 4 counties, the overall plague sero-positive rate was 2.31%(58/2508). This represents a statistically significant difference with 4 counties(X2=19.30,P<0.01). The sew-positive rate for males and females were 2.54% (32/1261) and 2.09% (26/1247), respectively. There were no statistically significant differences between males and females(X2= 0.65,P 0.05). The sero-positive rate in herdsman, cadre, Tibetan, Hart nationalities were 3.54% (44/1243), 6.47% (11 / 170), 2.40% (56/2335) and 1.47% (2/136), respectively. The sero- positive rate increased with age. The highest titre for human plague serum antibody was 1 : 640. Conclusion There were occult infections of plague in the population on source of three rivers area in Qinghai. Sero-epidemiologic data revealed that the human plague sero-positive rate was closely correlated with the local animal plague.
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<p><b>OBJECTIVE</b>To study the epidemiology of genotyping Yersinia pestis isolated in the fulminant epidemics of human plague in Qinghai province in 2004.</p><p><b>METHODS</b>Primer pairs targeting the twenty-three different identified regions (DFRs) were designed to detect the presence or deletion of each DFR in 13 strains of Yersinia pestis isolated from the fulminant epidemic of human plague in Qinghai province in 2004.</p><p><b>RESULTS</b>There were 4 genomovars, i.e. Genomovar 8, 10, 15 and 16 in the 13 strains of Yersinia pestis identified. The genomovar of all the strains of Yersinia pestis isolated from Nangqian county was Genomovar 10. Among the two strains of Yersinia pestis isolated from Wulan county, the genomovar of one strain was Genomovar 8 and the other was Genomovar 10. The genomovars of all the strains of Yersinia pestis isolated from Qilian, Qumalai and Chengduo county belonged to Genomovar 16.</p><p><b>CONCLUSION</b>It was demonstrated that the genotyping of Yersinia pestis appeared to be a powerful tool for investigating human plague epidemics.</p>