Guinea pig model of Mycobacterium tuberculosis latent/dormant infection.

Although guinea pigs are considered one of the best animal models of tuberculosis, little data exist describing latent or dormant tuberculosis infection in these animals. Here we address this issue using a streptomycin auxotrophic mutant of Mycobacterium tuberculosis. This mutant grows unimpaired in the presence of streptomycin but in its absence shifts to latency/dormancy (lack growth and over-expression of alpha-crystallin). To establish infection animals are inoculated with the mutant followed by daily administration of streptomycin (three weeks), which allows initial microbial multiplication in the animal's tissues. Withdrawal of streptomycin establishes latency/dormancy and few viable organisms are recovered from the animals' lungs and spleen six months later. During the infectious process guinea pigs steadily gained weight and presented no clinical signs (scuff fur and lethargy) of disease. Histopathology of organs mimicked tuberculous lesions in humans and PBMC from infected animals strongly responded to stimulation with PPD. Finally, tuberculin skin test (a hallmark of latent infection diagnosis) performed in infected animals was strongly positive (>or=15 mm induration). These results point to an interesting and reliable model of latent/dormant tuberculosis infection in guinea pigs.