title: Low dose aerosol fitness at the innate phase of murine infection better predicts virulence amongst clinical strains of Mycobacterium tuberculosis.
abstract: Evaluation of a quick and easy model to determine the intrinsic ability of clinical strains to generate active TB has been set by assuming that this is linked to the fitness of Mycobacterium tuberculosis strain at the innate phase of the infection. Thus, the higher the bacillary load, the greater the possibility of inducting liquefaction, and thus active TB, once the adaptive response is set.
  
  
  
  The virulence of seven clinical Mycobacterium tuberculosis strains isolated in Spain was tested by determining the bacillary concentration in the spleen and lung of mice at weeks 0, 1 and 2 after intravenous (IV) inoculation of 10⁴ CFU, and by determining the growth in vitro until the stationary phase had been reached. Cord distribution automated analysis showed two clear patterns related to the high and low fitness in the lung after IV infection. This pattern was not seen in the in vitro fitness tests, which clearly favored the reference strain (H37Rv). Subsequent determination using a more physiological low-dose aerosol (AER) inoculation with 10² CFU showed a third pattern in which the three best values coincided with the highest dissemination capacity according to epidemiological data.
  
  
  
  The fitness obtained after low dose aerosol administration in the presence of the innate immune response is the most predictive factor for determining the virulence of clinical strains. This gives support to a mechanism of the induction of active TB derived from the dynamic hypothesis of latent tuberculosis infection.
authors.affiliation: Unitat de Tuberculosi Experimental, Fundació Institut per a la Investigació en Ciències de la Salut Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona, Catalonia, Spain.
authors.forename: Neus
authors.initials: N
authors.lastname: Caceres
authors.forename: Isaac
authors.initials: I
authors.lastname: Llopis
authors.forename: Elena
authors.initials: E
authors.lastname: Marzo
authors.forename: Clara
authors.initials: C
authors.lastname: Prats
authors.forename: Cristina
authors.initials: C
authors.lastname: Vilaplana
authors.forename: Dario
authors.initials: D
authors.lastname: García de Viedma
authors.forename: Sofía
authors.initials: S
authors.lastname: Samper
authors.forename: Daniel
authors.initials: D
authors.lastname: Lopez
authors.forename: Pere-Joan
authors.initials: PJ
authors.lastname: Cardona
mesh_terms: D000328:Adult; D000336:Aerosols; D000818:Animals; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007113:Immunity, Innate; D007753:Laboratories; D008168:Lung / Q000276:immunology / Q000382:microbiology; D008297:Male; D051379:Mice; D008875:Middle Aged; D008954:Models, Biological; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification / Q000472:pathogenicity* / Q000502:physiology*; D013154:Spleen / Q000276:immunology / Q000382:microbiology; D014376:Tuberculosis / Q000453:epidemiology / Q000276:immunology* / Q000382:microbiology*; D017735:Virus Latency
chemical_list: D000336:Aerosols