%0 Journal Article
%T The use of Mycobacterium tuberculosis H37Ra-infected immunocompetent mice as an in vivo model of persisters.
%A Kumari N
%A Sharma R
%A Ali J
%A Chandra G
%A Singh S
%A Krishnan MY
%J Tuberculosis (Edinb)
%V 145
%N 0
%D 2024 03 18
%M 38262199
%F 2.973
%R 10.1016/j.tube.2024.102479
%X Persistence of Mycobacterium tuberculosis (Mtb) is one of the challenges to successful treatment of tuberculosis (TB). In vitro models of non-replicating Mtb are used to test the efficacy of new molecules against Mtb persisters. The H37Ra strain is attenuated for growth in macrophages and mice. We validated H37Ra-infected immunocompetent mice for testing anti-TB molecules against slow/non-replicating Mtb in vivo. Swiss mice were infected intravenously with H37Ra and monitored for CFU burden and histopathology for a period of 12 weeks. The bacteria multiplied at a slow pace reaching a maximum load of ∼106 in 8-12 weeks depending on the infection dose, accompanied by time and dose-dependent histopathological changes in the lungs. Surprisingly, four-weeks of treatment with isoniazid-rifampicin-ethambutol-pyrazinamide combination caused only 0.4 log10 and 1 log10 reduction in CFUs in lungs and spleen respectively. The results show that ∼40 % of the H37Ra bacilli in lungs are persisters after 4 weeks of anti-TB therapy. Isoniazid/rifampicin monotherapy also showed similar results. A combination of bedaquiline and isoniazid reduced the CFU counts to <200 (limit of detection), compared to ∼5000 CFUs by isoniazid alone. The study demonstrates an in vivo model of Mtb persisters for testing new leads using a BSL-2 strain.