Modeling of cerebral tuberculosis in BALB/c mice using clinical strain from patients with CNS -TB infection

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Background: This study describes development of a TBM animal model in mice using C3 strain isolated from CSF of TBM patients which can be used to study pathogenesis of C3 strain in mice. Methods & Materials: Female BALB/c mice aged 6–10 weeks were housed in a BSL- 3 facility. Two groups of mice (n = 12) were challenged intravenously through tail vein with 2 × 107 of C3 strain. Control group of mice (n = 10) was separately maintained and injected with sterile saline. Mice were killed at 30 and 50 days after development of infection, for estimating number of mycobacteria colonizing in brain,lungs and for histopathological changes. The mycobacterial burden was determined by plating and counting the number of CFUs. Serially diluted homogenates of individual lungs and brains were plated onto Middlebrook 7H11 medium. CFU's were counted after 3–4 weeks of infection. Histological sections were stained using hematoxylin and eosin. Results: Mice infected with C3 strain showed prominent edema of the brain in left hemisphere at 30 days, which increased at later stage compared to control mice. Histopathological examination of brain showed swelling of neurons along with lymphocytic infiltration which was progressively more at 50 days. The lung section at 30 days revealed >40 lession in lung parenchyma which improved at 50 days, with lession reduced to <20. Brain and lungs of control mice showed no major changes. Infection with C3 strain showed significant levels of mycobacterial load in brains with progress in infection. Analysis of CFU count revealed significantly high load in lungs (6.80 ± 0.1) at 30 days post infection, however the mycobacterial burden gradually decreased in lungs (5.8 ± 0.2) with progress in infection at 50 days. Analysis of CFU load in brain showed significantly high mycobacterial load at 50 days (4.0 ± 0.2) compared to infection at 30 days (5.0 ± 0.1). No mycobacterial load was observed in brains and lungs of control mice.C3 strain infection was associated with reduced survival-40% and high mortality rate -60%compared to control mice. Conclusion: Our present study demonstrated that intravenous inoculation by C3 strain from TBM patient's leads to progressive dissemination and development of TBM disease in mice.