Inoculation of mice.
BALB/c female mice weighing 17–18 g (Charles River) were kept under the BSL3 cabinet for 5 days before inoculation. This experiment aimed to determine whether mycobacteria isolated from soil 12 months post-contamination were still
virulent; thus, MTC mycobacteria grown from soil inoculated for 12 months were used. The mice were separated into four groups of five each. Three groups were infected intraperitoneally with 100 ml of a 16106 c.f.u. ml21 suspension of M. tuberculosis, M. bovis or M. canettii that had been cultured from soil inoculated for 12 months; one negative control group was inoculated with 100 ml sterile PBS. The weight, clinical examination and survival of mice were followed weekly for 90 days. All mice (all survivors) were killed by exsanguination at day 90 post-infection. The lungs, spleen and liver were removed. One portion of each organ was homogenized in