Comparative study of a rabbit model of spinal tuberculosis using different concentrations of Mycobacterium tuberculosis.

Background: Tuberculosis is among the most devastating infectious diseases worldwide. Spinal tuberculosis is not easy to detect at an early stage, which without effective treatment often leads to spinal deformity and spinal cord damage which in turn cause complications such as paraplegia and quadriplegia. In this study, we established a model using three concentrations of bacteria and carried out a comprehensive evaluation of the model by imaging, general observations, and histopathological and bacteriological studies.

Aim: To establish a rabbit model of spinal tuberculosis and examine the effect on the model's efficacy using different concentrations of Mycobacterium tuberculosis (M. tuberculosis) inoculum.

Methods: New Zealand rabbits were randomly divided into experimental, control and blank groups. The experimental and control animals were sensitized with complete Freund's adjuvant, a hole was drilled beneath the upper endplate of the L6 vertebral body and filled with gelfoam sponge. The experimental group was divided into three subgroups (experimental 1, experimental 2, experimental 3) and infused with M. tuberculosis suspension at various concentrations. The control group was inoculated with saline and the blank group received no treatment. The 12-week post-operative survival rates were 100%, 80% and 30% in the experimental groups inoculated with concentrations of 10⁶, 10⁷ and 10⁸ CFU/mL bacteria, respectively.

Results: The survival rate of the control and blank groups was 100%. Vertebral body destruction at 8 weeks in the three experimental groups as determined by X-ray analysis was 33.3%, 62.5% and 66.7%, and by computed tomography (CT) and 3-dimensional CT 44.4%, 75% and 100%, respectively. At 12 weeks, the figures were 44.4%, 75% and 100% by X-ray analysis and 44.4%, 100% and 100% by CT and 3-dimensional CT, respectively. All surviving rabbits of the experimental groups had vertebral destruction. The positive bacterial culture rates were 22.2%, 75% and 66.7%, respectively, in the experimental groups. After being sensitized with complete Freund's adjuvant, large differences were observed in the extent of spinal tuberculosis after inoculation of the rabbits with different concentrations of H37RV standard M. tuberculosis.

Conclusion: The experimental 1 had a low success rate at establishing an infection. The experimental 3 resulted in high mortality and complication rates. The experimental 2 was optimum for establishing a spinal tuberculosis model based on the high level of symptoms observed and the low rabbit mortality.