Objective: To investigate the presence of rifampicin-dependent Mycobacterium tuberculosis strains by use of a guinea pig model of tuberculosis of rifampicin-dependent Mycobacterium tuberculosis.
Methods: Guinea pigs were randomly divided into groups of infection by rifampicin-dependent Mycobacterium tuberculosis strains (1130 strain, 1219 strain, b858 strain), rifampicin-resistant Mycobacterium tuberculosis strain (1290 strain) and ATCC 35810 strain and each group was further divided into an experimental group and a control group. The guinea pigs were challenged with 1130 strain, 1219 strain, b858 strain, 1290 strain and ATCC 35810 strain to establish the tuberculosis model. The experimental groups were treated with rifampicin. The parameters including macroscopic visceral pathological change index, visceral weight index (spleen, lungs and liver), the colony-forming units (CFU) quantity of visceral Mycobacterium tuberculosis culture (spleen, lungs) and tissue pathology of guinea pigs were observed.
Results: At the 7th week after challenged with 1130 strain, 1219 strain, 1290 strain and b858 strain, all animals were sacrificed. The macroscopic visceral pathological change indices of the experimental group were 68.7 +/- 13.8, 60.0 +/- 13.5, 70.0 +/- 5.8 and 23.8 +/- 18.9, whereas all those parameters of the control group were 76.2 +/- 18.9, 40.0 +/- 16.8, 63.8 +/- 10.3 and 22.5 +/- 15.5 respectively, and there was no significance between the experimental group and the control group (t = 0.64, 1.85, 0.35 and 0.10, all P > 0.05). The spleen weight indices of experimental group were 0.229 +/- 0.048, 0.256 +/- 0.067, 0.324 +/- 0.054 and 0.199 +/- 0.029, whereas all those parameters of control groups were 0.278 +/- 0.025, 0.216 +/- 0.076, 0.368 +/- 0.033 and 0.213 +/- 0.038 respectively, and there was no significance between the experimental group and the control group (t = 1.75, 0.79, 1.41 and 0.57, all P > 0.05). The CFU quantity of spleen Mycobacterium tuberculosis culture of the experimental group were 4.98 +/- 0.30, 4.68 +/- 1.26, 5.07 +/- 0.47 and 3.85 +/- 0.45, whereas all those parameters of control groups were 4.90 +/- 1.03, 4.79 +/- 0.45, 5.08 +/- 0.55 and 4.23 +/- 0.95 respectively, and there was no significance between the experimental group and the control group (t = 0.11, 0.15, 0.03 and 0.73, all P > 0.05); Moreover, the tissue pathology of both groups was similar.
Conclusions: The tuberculosis model of rifampicin-dependent Mycobacterium tuberculosis strains was similar to the model of rifampicin-resistant Mycobacterium tuberculosis in guinea pigs. Rifampicin-dependency was not evident in this guinea pig tuberculosis model.