title: Changes of predominant species/biovars and sequence types of Brucella isolates, Inner Mongolia, China.
abstract: BACKGROUND
  Human brucellosis incidence in China was divided into 3 stages, high incidence (1950-1960s), decline (1970-1980s) and re-emergence (1990-2000s). Human brucellosis has been reported in all the 32 provinces, of which Inner Mongolia has the highest prevalence, accounting for over 40% of the cases in China. To investigate the etiology alteration of human brucellosis in Inner Mongolia, the species, biovars and genotypes of 60 Brucella isolates from this province were analyzed.
  
  
  METHODS
  Species and biovars of the Brucella strains isolated from outbreaks were determined based on classical identification procedures. Strains were genotyped by multi locus sequence typing (MLST). Sequences of 9 housekeeping genes were obtained and sequence types were defined. The distribution of species, biovars and sequence types (STs) among the three incidence stages were analyzed and compared.
  
  
  RESULTS
  The three stages of high incidence, decline and re-emergence were predominated by B. melitensis biovar 2 and 3, B. abortus biovar 3, and B. melitensis biovar 1, respectively, implying changes in the predominant biovars. Genotyping by MLST revealed a total of 14 STs. Nine STs (from ST28 to ST36), accounting for 64.3% of all the STs, were newly defined and different from those observed in other countries. Different STs were distributed among the three stages. ST8 was the most common ST in 1950-1960s and 1990-2000s, while ST2 was the most common in 1970-1980s.
  
  
  CONCLUSIONS
  The prevalence of biovars and sequence types of Brucella strains from Inner Mongolia has changed over time in the three stages. Compared with those from other countries, new sequence types of Brucella strains exist in China.
authors.forename: Yanfen
authors.initials: Y
authors.lastname: Chen
authors.forename: Yuehua
authors.initials: Y
authors.lastname: Ke
authors.forename: Yufei
authors.initials: Y
authors.lastname: Wang
authors.forename: Xitong
authors.initials: X
authors.lastname: Yuan
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhou
authors.forename: Hai
authors.initials: H
authors.lastname: Jiang
authors.forename: Zhoujia
authors.initials: Z
authors.lastname: Wang
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhen
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Department of Infectious Disease Control, Beijing Institute of Disease Control and Prevention, Beijing 100071, P,R, China. huangly@nic.bmi.ac.cn.
authors.forename: Liuyu
authors.initials: L
authors.lastname: Huang
authors.forename: Buyun
authors.initials: B
authors.lastname: Cui
authors.forename: Zeliang
authors.initials: Z
authors.lastname: Chen
mesh_terms: D002002:Brucella / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D002006:Brucellosis / Q000453:epidemiology* / Q000382:microbiology*; D002681:China / Q000453:epidemiology; D005838:Genotype; D006801:Humans; D058885:Multilocus Sequence Typing; D012189:Retrospective Studies