TABLE 1.

Inactivation of M. tuberculosis H37Rv in centrally necrotizing granulomas by gamma irradiation of lung tissue biopsy specimens from M. tuberculosis-infected BALB/c IL-13^tg mice^a

Exposed dose (kGy)	TTP (days)	AFB, cord formationb
None	4 ± 0.5	+
16.10	22 ± 11.0	+
32.20	19 ± 5.4	+
48.30	28 ± 16.2	+

^aBALB/c IL-13^tg mice were infected with 70 CFU of M. tuberculosis H37Rv, and at time points later than 100 days after infection, lung tissue biopsy specimens were prepared. At least 3 biopsy specimens were gamma irradiated at the indicated doses. The tissue was homogenized after irradiation, and the homogenate was split into 4 aliquots prior to inoculation of MGIT tubes. Inactivation of M. tuberculosis was evaluated by determining the TTP using the MGIT system, followed by microscopic detection of AFB and cord formation in cultures. TTP data are the mean ± SD.

^b+, positive for AFB and cord formation.