Seven weeks following immunization with BCG-P or ΔleuD ΔpanCD, immunized animals and naive controls were challenged with 33 CFU M. tuberculosis. Survival of infected guinea pigs was followed for up to 452 days post-challenge. Naive animals succumbed to challenge with a median survival time (MST) of 154 days, whereas ΔleuD ΔpanCD- and BCG-immunized guinea pigs survived significantly longer (MST 446 d and 452 d, respectively). *, p<0.0001 as determined by Logrank test comparisons of survival curves, n=11 animals per experimental group.