Tuberculosis Made Easy (Everything about it)

A presentation about Tuberculosis . This presentation composed of the definition, causes, pathophysiology, clinical feature, diagnosis, treatment, prognosis and prevention of Tuberculosis.

1. Covered by: Arwa H. Al- Onayzan .

2. Tuberculosis

3. Definition: Tuberculosis (TB ): Is a chronic, progressive infection, often with a period of latency following initial infection. TB most commonly affects the lungs . TB is a leading infectious cause of morbidity and mortality in adults worldwide, killing about 1.3 million people in 2012. Most of them in low- and middle-income countries. HIV/AIDS is the most important factor predisposing to TB infection and mortality in parts of the world where both infections are prevalent.  

4. Types: *if existed It can be classified as: Open tuberculosis (Is consider infectious and occur when the TB bacteria in the lung spread into the air and infect others). Closed tuberculosis (Is not consider infectious because it cannot spread into the air, such as, lymph node TB). It can be classified as: Pulmonary tuberculosis (Affect only the lung). Extrapulmonary tuberculosis (Affect lymph node, bone, ect ). It can be classified according to pathogesis  see next slide (table)

5. Causes: TB properly refers only to disease caused by  Mycobacterium tuberculosis  (for which humans are the main reservoir). It can also results from other mycobacteria ,  M. bovis ,  M. africanum , and  M. microti —together known as the  M. tuberculosis  complex . TB results almost from inhalation of airborne particles (droplet nuclei) containing  M. tuberculosis . They disperse primarily through coughing, singing, and other forced respiratory maneuvers by people who have active pulmonary TB and whose sputum contains a significant number of organisms. TB of the tonsils, lymph nodes, abdominal organs, bones, and joints was once commonly caused by ingestion of milk or milk products ( eg , cheese) contaminated with  M. bovis .  

6. Pathophysiology: M. tuberculosis  bacilli initially cause a primary infection. it asymptomatic and followed by a latent (dormant) phase.  Infection requires inhalation of particles small enough to traverse in the lung, usually in the subpleural airspaces of the middle or lower lobes.  To initiate infection,  M. tuberculosis  bacilli must be ingested by alveolar macrophages. Bacilli that are not killed by the macrophages, replicate inside them, ultimately killing the host macrophage (with the help of CD8 lymphocyte); inflammatory cells are attracted to the area, causing a focal pneumonitis. Some infected macrophages migrate to regional lymph nodes ( eg , hilar , mediastinal ), where they access the bloodstream and spread over body. The balance between the host’s resistance and microbial virulence determines whether the infection ultimately resolves without treatment, remains dormant, or becomes active. Infectious foci may leave fibronodular scars in the apices of one or both lungs (Simon foci, which usually result from hematogenous seeding from another site of infection) or small areas of consolidation ( Ghon foci). A Ghon focus with lymph node involvement is a Ghon complex, which, if calcified, is called a Ranke complex.  Tuberculin skin test and interferon-gamma release blood assays (IGRA) become positive during the latent stage of infection.

7. Signs and symptoms: In active pulmonary TB, patients may have no symptoms, except “not feeling well,” anorexia, fatigue, and weight loss, which develop gradually over several weeks, or they may have more specific symptoms: Cough is most common. At first, it may be minimally productive of yellow or green sputum, usually when awakening in the morning, but cough may become more productive as the disease progresses.  Hemoptysis occurs only with cavitary TB (due to granulomatous damage to vessels). Low-grade fever is common but not invariable.  Night sweats are a classic symptom but are neither common in nor specific for TB . Dyspnea may result from lung parenchymal damage. Extrapulmonary TB causes various systemic and localized manifestations depending on the affected organs.

8. How to Diagnose: Chest x-ray ( a multinodular infiltrate above or behind the clavicle is most characteristic of active TB)  see pic. Acid-fast stain and culture (Gold standard, samples are best prepared with Ziehl-Neelsen or Kinyoun stains for conventional light microscopy). Tuberculin skin test (TST )  see pic or interferon-gamma release assay (IGRA ) (is a blood test based on the release of interferon-γ by lymphocytes exposed in vitro to TB-specific antigens). When available, nucleic acid–based testing ( has not been approved but can be extremely useful, used for fixed tissues eg , for biopsied lymph node).  

9. Treatment: Most patients with TB can be treated as outpatients, with instructions including : Staying at home. Avoiding visitors (except for previously exposed family members ). Covering coughs with a tissue or elbow. The main indications for hospitalization are: Serious concomitant illness Need for diagnostic procedures Social issues ( eg , homelessness) Need for respiratory isolation, as for people living in congregate settings Treatment regimen: 2-mo initial intensive phase and 4- to 7-mo continuation phase. The first-line drugs  isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), and  ethambutol  (EMB) are used together in initial treatment. The second-line drugs used if there is resistance such as, aminoglycosides ( streptomysin ) and fluoroquinolones ( levofloxacin,  moxifloxacin ).

10. Prognosis: In immunocompetent patients with drug-susceptible pulmonary TB, even severe disease with large cavities, appropriate therapy is usually curative if it is instituted and completed. TB causes or contributes to death in about 10% of cases, often in patients who are debilitated for other reasons . Disseminated TB and TB meningitis may be fatal in up to 25% of cases despite optimal treatment. TB is much more aggressive in immunocompromised patients and, if not appropriately and aggressively treated, may be fatal.

11. Prevention: General preventive measures ( eg , staying at home, avoiding visitors, covering coughs with a tissue or hand). Vaccination: The BCG vaccine, made from an attenuated strain of  M. bovis   is given to > 80% of the world’s children. Average efficacy is probably only 50%.  BCG clearly reduces the rate of extrathoracic TB in children, especially TB meningitis, and may prevent TB infection . IGRAs are not influenced by BCG vaccination. TST is influenced by BCG vaccination.

12. References: Merk manual website : http:// www.msdmanuals.com/professional/infectious-diseases/mycobacteria/tuberculosis-tb Medscape website: http:// emedicine.medscape.com/article/230802-overview#a5