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Objective:To study the phenotype and genotype distribution of Yersinia pestis ( Y. pestis) in different natural foci of plague in China, so as to provide scientific basis for plague prevention and control. Methods:A total of 2 184 strains of Y. pestis isolated from different time periods, regions, hosts and vectors in 11 plague natural foci of China since 1943 were selected for biochemical type identification, glycolysis test, virulence factor test [capsule antigen (F1), pesticin Ⅰ (Pst Ⅰ), virulence antigen factor (VWa), pigmentation factor (Pgm)], different region (DFR) typing and clustered regularly interspaced short palindromic repeats (CRISPR) typing. Results:There were 16 biochemical types of Y. pestis in the natural foci of plague in China, and each biochemical type showed obvious regional distribution in each foci. Most strains were positive for ass hide glue glycolysis (89.79%, 1 961/2 184), maltose (80.13%, 1 750/2 184), glycerol (94.23%, 2 058/2 184), and denitrification (82.78%, 1 808/2 184), and negative for rhamnose (88.78%, 1 939/2 184) and melibiose (85.62%, 1 870/2 184). Virulence factor test results showed that 99.95% (2 183/2 184) of Y. pestis were F1 positive; 99.73% (2 178/2 184) of Y. pestis can produce Pst Ⅰ; 73.31% (1 601/2 184) of Y. pestis were VWa positive and 26.69% (583/2 184) were VWa negative; Pgm positive strains accounted for 72.62% (1 586/2 184), Pgm negative strains accounted for 21.52% (470/2 184), and Pgm mixed type strains accounted for 5.86% (128/2 184). According to DFR typing results, there were 52 genotypes in 2 184 strains of Y. pestis, of which 19 were major genotypes and 33 were minor genotypes. CRISPR typing revealed 16 major genotypes, of which 7 were newly discovered. Conclusion:The phenotypes and genotypes of Y. pestis in various natural foci of plague in China are diverse and have geographical distribution characteristics.
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Objective:To investigate the genotypes of clustered regularly interspaced short palindromic repeats (CRISPR) of Yersinia pestis ( Y. pestis) and it's regional distribution in the plague natural foci of Qinghai-Tibet Plateau. Methods:In this study, 1 004 strains of Y. pestis isolated from different hosts and vectors in different regions from 1954 to 2011 were selected as experimental objects, which preserved in Qinghai Institute for Endemic Disease Prevention and Control, and DNA of Y. pestis was extracted by traditional phenol-chloroform method. Three CRISPR loci (YPa, YPb and YPc) were amplified by PCR and sequenced, respectively, and the CRISPR sequences were compared with the CRISPRDictionary database recently reported in the literature to identify CRISPR spacer. For the spacer discovered for the first time at each CRISPR locus, Blast sequence alignment was performed in the National Center for Biotechnology Information (NCBI) database to speculate the source of gene sequence. Genotyping of Y. pestis from Qinghai-Tibet Plateau was performed based on the polymorphism of CRISPR spacer array. Results:A total of 53 spacers were found in 1 004 strains of Y. pestis, of which 6 spacers were newly discovered, namely a105, a106, a107, b51, b52 and c14. The 1 004 strains of Y. pestis were divided into 10 groups with 44 different CRISPR genotypes, and 15 new genotypes were found. The dominant genotypes of Y. pestis were G26-a1', G7, G22, G24-a1', G22-a1', G9 and G26-a1'a60 in Himalayan Marmot plague natural foci, and G37-a6' in Qinghai Microtinae plague natural foci. Conclusion:The CRISPR genotypes of Y. pestis in the plague natural foci of Qinghai-Tibet Plateau are high diverse and have significant regional distribution characteristics.
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Objective:To analyze the pathogenic characteristics of Yersinia pestis in a plague natural foci in Qinghai-Tibet Plateau. Methods:In this study, 1 378 strains of Yersinia pestis isolated from different regions, hosts and vectors in Qinghai-Tibet Plateau from 1954 to 2016 were taken as the research objects. Phenotypic characteristics, plasmid spectrum and genotype of the strains were studied by using conventional techniques and molecular biological techniques. The etiology and geographical distribution of the plague were studied. Results:There were 6 biochemical types of Yersinia pestis in Qinghai-Tibet Plateau, namely Qinghai-Tibet Plateau, Qilian Mountain, Gangdis Mountain, Kunlun Mountain A, Kunlun Mountain B and Chuanqing Plateau. This study found that the Qinghai-Tibet Plateau type strain was not only distributed in north Tibet Plateau, but also distributed in south Tibet, and the distribution of Gangdis Mountain type strain extended to south Tibet. Four virulence factors (capsule antigen, yersinin, virulence antigen and pigmentation factor) were found in 79.97% (1 102/1 378) Yersinia pestis. The results also showed that there were 12 kinds of plasmids carried by Yersinia pestis strains in Qinghai-Tibet Plateau, which constituted 17 kinds of plasmid spectrum. There were 3 kinds of the largest plasmids with taxonomic properties, forming their respective relatively independent distribution areas. The study of different regions (DFR) type showed that 5, 8, 14, 19, 32 and 44 of 1 378 strains were the main genotypes, and the main genome types had obvious geographical distribution. Conclusions:All the tested strains have the characteristics of plague pathogen in Qinghai-Tibet Plateau. The polymorphism of the main hosts, vectors and the ecological landscape of plague geography in the plague foci in Qinghai-Tibet Plateau may lead to the diversity of biochemical characters, plasmid spectrum and geno types of Yersinia pestis.
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Objective To compare and analyze the soil eight metal elements contents of rat holes of three plague foci in Yunnan Province.Methods The soils were collected from the rat holes in Yulong,Jianchuan,and Lianghe plague foci.Calcium (Ca),iron (Fe),zinc (Zn),chromium (Cr),lead (Pb),manganese (Mn),cadmium (Cd),and copper (Cu) were quantified with flame atomic absorption spectrometry (FAAS).Data input,calculation and collation were conducted through Excel 2007,and statistical software SPSS 20.0 was used to carried out statistical analysis through rank sum test.Results The medians of Ca content in the rat hole soil of Yulong County,Jianchuan County,and Lianghe County,respectively,were 85.40,308.56,and 0.00 mg/kg;the medians of Fe were 2 569.07,1 950.16,and 975.72 mg/kg;the medians of Zn were 5.64,4.02,and 2.04 mg/kg;the medians of Cr were 1.09,3.06,and 0.71 mg/kg;the medians of Pb were 3.61,29.56,and 22.80 mg/kg;the medians of Mn were 223.01,212.97,and 80.43 mg/kg;the medians of Cd were 0.00,2.02,and 2.94 mg/kg;and the medians of Cu were 1.92,1.08,and 0.51 mg/kg.The contents of eight metal elements were statistically different in the soil samples between Yulong,Jianchuan,and Lianghe plague foci (H =80.538,127.687,202.583,185.359,124.747,150.057,91.346,228.546,P ＜ 0.05).Conclusions The content of Fe in soil of the three plague foci in Yunnan Province is abundant.The contents of metal elements of Yulong County and Jianchuan County are similar.
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We investigated the current situation about free-ranging dogs infection with plague and provided relevant data for plague prevention and control in Karamay City.We examined the dog serum F1 antibody by indirect hemagglutination assay (IHA).Results showed that the F1 antibody was found in 1 of 13 dogs serum samples,and the positive rate was 7.69％.The free-ranging dogs plays an important role in controlling animal plague epidemic,and there are potential risk for local people's infection of plague.
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The plague occurs due to the long-term persistence of Yersinia pestis in natural environment.During the period of plague epidemic and quiescence,there are still some unknown scientific questions,such as where Yersinia pestis preserved,which mode preserved,and which mechanism caused plague epidemic.Thus,the researches on the preservation and viability of Yersinia pestis in every ecological element of plague natural foci will contribute to find the pattern for the occurrence and spread of plague.