title: [A guinea pig model of latent Mycobacterium tuberculosis H₃₇Rv infection].
abstract: OBJECTIVE
  To establish the guinea pig model of latent Mycobacterium tuberculosis (MTB) H₃₇Rv infection, and to study the multiplication dynamics of MTB in vivo, and the relationship between latent MTB infection and PPD skin test.
  
  
  METHODS
  Sixty-two guinea pigs were randomly divided into the model group (n = 42) and the control group (n = 20), and the model group was subdivided into a 4 weeks group (n = 12), an 8 weeks group (n = 21) and a 12 weeks group (n = 9), challenged by 500 CFU H₃₇Rv with restored toxicity. After 2 weeks challenge, the model groups were treated with isoniazid (INH, 10 mg/kg) + pyrazinamidum aldinamide (PZA, 40 mg/kg) for 4 weeks, 8 weeks and 12 weeks respectively. The natural recurrence of tuberculosis was observed in the model 4 weeks group, and the natural and induced recurrence by dexamethasone was observed in the model 8 weeks group and 12 weeks group. PPD skin test, the pathologic changes, and MTB quantity of organs were observed.
  
  
  RESULTS
  In the control group, the average MTB quantity of spleen was 3.3 lg CFU after 2 weeks challenge, and the average MTB quantity of spleen and lung in guinea pigs were 4.5 lg CFU and 1.8 lg CFU respectively after 6 weeks challenge, and they reached 5.3 lg CFU and 5.4 lg CFU at 18 weeks respectively. The latent MTB infection of the model 4 weeks group recurred naturally 12 weeks after stopping treatment. The latent MTB infection of the model 8 weeks group recurred naturally and by dexamethasone treatment. The latent MTB infection of the model 12 weeks group did not recur naturally, but dexamethasone induced recurrence. The positive PPD response correlated with recurrence.
  
  
  CONCLUSIONS
  A latent MTB infection model was established successfully by H₃₇Rv challenge and treatment with INH and PZA. The latent MTB infection may recur naturally or by induction. The PPD response was related to tuberculosis recurrence.
authors.affiliation: Department of Respiratory Medicine, the First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China.
authors.forename: You-lun
authors.initials: YL
authors.lastname: Li
authors.forename: Bao-wen
authors.initials: BW
authors.lastname: Chen
authors.forename: Miao
authors.initials: M
authors.lastname: Xu
authors.forename: Yong-ai
authors.initials: YA
authors.lastname: Luo
authors.forename: Guo-zhi
authors.initials: GZ
authors.lastname: Wang
authors.forename: Xiao-bing
authors.initials: XB
authors.lastname: Shen
authors.forename: Cheng
authors.initials: C
authors.lastname: Su
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006168:Guinea Pigs; D008297:Male; D009169:Mycobacterium tuberculosis / Q000472:pathogenicity*; D014376:Tuberculosis / Q000382:microbiology / Q000473:pathology*