I am reading Murray Microbiology book.
- M. tuberculosis is an intracellular pathogen.
- At the time of exposure, M. tuberculosis enters the respiratory airways and infectious particles penetrate to the alveoli where they are phagocytised by alveolar macrophages.
- In contrast with most phagocytised bacteria, M. tuberculosis prevents fusion of the phagosome with lysosomes (by blocking the specific bridging molecule, early endosomal autoantigen 1 [EEA1]). NB probably here something relevant
- At the same time, the phagosome is able to fuse with other intracellular vesicles, permitting access to nutrients and facilitating intravacuole replication.
- Phagocytised bacteria are also able to evade macrophage killing mediated by reactive nitrogen intermediates formed between nitric oxide and superoxide anions by catalytically catabolising the oxidants that are formed.
- Dissemination to any body site occurs most commonly in immunocompromised patients, like HIV patient.