Mycobacterium tuberculosis can survive for a long time in the body of a healthy host, causing no symptoms after primary infection. Years or decades later, M. tuberculosis can be reactivated in some carriers, leading to symptoms of post-primary tuberculosis. During the asymptomatic period, M. tuberculosis is believed to survive in old foci of infection, yet these foci are uniformly negative by culture and acid-fast staining, which are conventional methods to detect mycobacteria. The precise location and amount of M. tuberculosis in these foci, therefore, are not well understood. The report show that granulomatous lesions with calcification, a well-known characteristic of old tubercles, contained considerable amounts of M. tuberculosis genomes and cell wall components. These calcified lesions exhibited little inflammation but all were positive for M. tuberculosis by real-time polymerase chain reaction and by immunohistochemistry with a novel monoclonal antibody against lipoarabinomannan, a cell wall component of mycobacteria.
Last date updated on January, 2021