Comparison of the protective efficacy of bacille Calmette-Guerin vaccination against aerosol challenge with Mycobacterium tuberculosis and Mycobacterium bovis

The aim of this study was to compare protection by bacille Calmette-Guerin (BCG) vaccination against aerosol challenge with either Mycobacterium bovis or Mycobacterium tuberculosis in guinea pigs, Animals were challenged 5 we eks after vaccination with 10 or 100 lung lesion-forming units (lfu) of M. bovis or M. tuberculosis. Four weeks after challenge, numbers of lung lesio ns and counts of viable mycobacteria in spleens were high in saline-immuniz ed animals. Ln contrast, BCG vaccination resulted in fewer lung lesions; af ter challenge with 10 and 100 lfu, the reduction was greater in animals inf ected with M. bovis (mean number of lesions, 1.17 and 31.2, respectively; P <.02) than in those infected with M, tuberculosis(mean number of lesions, 1 6.2 and 75,8, respectively). No mycobacteria were recovered from spleens of BCG-vaccinated animals after challenge with 10 lfu of M. bovis, whereas 4 of 6 animals had detectable spleen mycobacterial counts after challenge wit h nk tuberculosis. Collectively, the results suggest that BCG vaccination m ay confer greater protection against challenge with M. bovis than challenge with M. tuberculosis.