FIG. 5.

Assay of immune protection induced in mice 6 months after immunization by rectal or subcutaneous administration of BCG. Results are shown for BALB/c mice (n = 8-10) nonimmunized (empty bars) or immunized with BCG by the rectal (fine hatches) or by subcutaneous injection (coarse hatches) routes. Six months later, the mice were challenged intravenously with 10⁵ viable units of the virulent M. tuberculosis strain H37Rv. The spleen and lungs were collected 4 weeks later and dissociated. Their bacterial loads were evaluated after appropriate dilutions and growth on Middlebrook 7H11 agar medium. Results are expressed as geometric mean + standard deviation (error bar) ∗∗∗, P < 0.001.