Figure 1.

Mice were infected with approximately 10² colony-forming units (CFU) of Mycobacterium tuberculosis (Mtb) via the airborne route, 10⁵ CFU via the intravenous (i.v.) route, or 10² via the airborne plus 10⁵ via the i.v. route. Lung infection in mice infected concurrently via the i.v. and airborne routes was controlled earlier than in mice infected via the respiratory route alone, but was controlled earlier still in mice infected via the i.v. route alone. Spleen infection was initiated immediately and controlled after approximately 10 days in mice infected via the i.v. route, or via both routes. It was not initiated until after about a 12-day delay in mice infected via the respiratory route alone, and was not controlled until after day 20. The draining lymph nodes (LNs) became infected on day 10 in mice infected via the respiratory route alone, and probably earlier in mice infected via the i.v. route, or via both routes. Control of LN infection occurred on day 15 in mice infected via the i.v. route or via both routes, and on day 20 in mice infected via the respiratory route alone. Means ± SD of four mice per group per time-point.