Table 1. Comparative lung histopathology in guinea pigs infected with M. tuberculosis H37Rv with different histories of in vitro and in vivo passaging.

H37Rv Strain	Week	Mean # granulomas	granulomas/field	Mean Score (1–4)
TAMU*	3	30	>13	3.25
JHU**	3	26.5	10.6	2.5
TAMU*	6	16	6.4	3.5
JHU**	6	19.5	7.8	2.4

* Not passaged in mice.

** Passaged in mice.