​Infectious Diseases and Microbiology - Tuberculosis ( Mycobacterium tuberculosis)

​Infectious Diseases and Microbiology - Tuberculosis ( Mycobacterium tuberculosis) 
Mycobacterium tuberculosis is a slow-growing, acid-fast rod with mycolic acids present in its cell wall and causing tuberculosis.
Transmission occurs through respiratory aerosols. The increased infectivity results in a positive conversion of the skin test. The prevalence of active disease is higher in those with impaired immune systems.The causative agent of tuberculosis is Mycobacterium tuberculosis. Active pulmonary illness presents with symptoms such as cough, hemoptysis (coughing up blood), fever, weight loss, and night sweats. The lungs may exhibit the presence of numerous granulomas characterized by caseation. Disseminated or miliary tuberculosis occurs as a consequence of tubercle erosion. Bacteria disseminate via the circulatory system and generate granulomas in many organs. Mycobacterium tuberculosis chronic meningitis is linked to a significant mortality rate.

The main method by which M tuberculosis causes disease is its capacity to live and reproduce within macrophages that have not been activated. This leads to the development of granulomas, also known as tubercles, which contain caseous necrotic cores. The transformation of the caseous centers into a liquid state and the formation of cavities occur as the disease becomes more aggressive. Organisms have the ability to endure within tubercles for extended periods, resulting in reactivation when the immune system is weakened, such as in cases of HIV infection.

Direct analysis of sputum may detect acid-fast bacilli in cases of active illness. Exposure is assessed through the evaluation of reactivity to the Diagnosis PPD skin test. This test measures the cell-mediated immune response to the protein component of the cell wall, also known as purified protein derivative (PPD). Culture growth is characterized by a slow pace, typically taking 3-4 weeks, and necessitates the use of specialized media. However, it is crucial for conducting susceptibility testing.

Treatment involves the use of combination therapy with antibiotics for an extended duration of 6 to 9 months. Treatment is determined through susceptibility testing, which may involve the use of isoniazid (INH), ethambutol, rifampin, pyrazinamide, streptomycin, ethionamide, cycloserine, and fluroquinolones. Preventive measures consist of administering a live mycobacterium from a similar species (bacillus Calmette-Guerin, or BCG) by vaccination (except in the United States), and providing chemoprophylaxis to those who have recently tested positive for PPD conversions.