Final answer:
Mycobacterium tuberculosis is inhaled and survives in macrophages within the alveoli, which leads to an inflammatory response and formation of tubercles. The bacteria multiply and may cause tissue damage, which can allow them to spread through the bloodstream and form secondary infections. Special precautions are needed due to its airborne transmission.
Step-by-step explanation:
Path of M. tuberculosis After Infection
After Mycobacterium tuberculosis is inhaled, the bacteria travel to the alveoli where they are phagocytosed by macrophages. Due to the protective waxy mycolic acid in their walls, the bacteria can survive and multiply within the cells. The infection may provoke an inflammatory response and trigger the accumulation of immune cells, such as neutrophils and macrophages. It takes several weeks or months for a complete immunological response from T cells and B cells. The immune response results in the formation of tubercles, which are lesions that wall off the infection.
As the chronic immune response continues, tissue damage occurs and apoptotic cell death (liquefaction) leads to the formation of a caseous center, conducive for the bacteria's multiplication. Tubercles may rupture, allowing the bacilli to spread into pulmonary capillaries and via the bloodstream to various organs, a stage known as miliary tuberculosis. Special precautions, like face masks and negative-pressure ventilation, are necessary when caring for TB patients due to the risk of airborne transmission.
The disease caused by M. tuberculosis is chronic and granulomatous, often associated with the lungs. The infectious dose is remarkably small, and upon introduction through respiratory droplets, the bacteria commence a cycle of infection that can perpetuate in an immunocompromised individual, leading to secondary tuberculosis.