Tuberculosis Flashcards
(24 cards)
What is the name of the pathogen that causes TB?
Mycobacterium tuberculosis
How is TB transmitted?
Airborne droplets
What are the risk factors for TB
Immunosuppression (HIV, immunosuppressant drugs, TNFalpha inhibitors)
DM, ESRF
Previous lung disease
Smoking
Malnutrition
Drug abuse and alcoholism
Occupational (hospitals)
Living conditions (prisions, homeless shelters)
What are the virulence factors for TB?
Mycolic acid glycolipids
Trehalose dimycolate
Catalase-peroxidase
Lipoarabinomannan
Explain how the infectious process for TB works
Inhalation of TB droplets > enters alveoli > alveolar macrophages engulf > proliferates in macrophages > release > immune response
What are the three stages of TB?
Primary - active TB infection following my
Latent - TH1 response > caseating granuloma
Reactivation - 1) active infection years after latent infection 2) immunosuppression occurs
What are the constitutional symptoms of TB?
Fever
Night sweats
Weight loss / anorexia / malaise
What are the pulmonary symptoms of TB?
Cough 2-3 weeks
Dry cough then productive
Haemoptysis
Chest sounds - bronchial breath sounds, crackles or NAD
Extrapulmonary TB?
Pleura, bones, lymphatic system, liver, CNS, urogenital tract, GI tract, skin
What investigations are used for latent TB?
Tuberculin skin test
IGRA - interferon gamma- release assay
What is TST?
Purified protein derivative of tuberculin. Injected intradermally.
How is TST measured?
48-72hrs after infection, diameter of rash is measured
When is IGRA preferred in suspected latent TB ?
BCG vaccinations
What is measured in IGRA?
Interferon-y (lambda)
What initial scan do you use for TB?
CXR
What investigations are used for suspected active TB?
Sputum microscopy - 3 samples TBS
Culture - solid or liquid
NAAT - Xpert MTB / RIF (detects rifampin-resistance mutations or amplified M. tuberculosis direct test
What stain is used to identify TB in sputum microscopy?
Ziehl-Neelson stain
What is the treatment for latent TB? What is the duration of treatment ?
Isoniazid for 9 months
Rifampin for 4 months
What is the treatment for active TB? Duration?
Isoniazid + rifampin + pyrozinamide + ethambutol for 2 months
Isoniazid and rifampin for 4 months
How is TB monitored once treatment is started?
Monthly interval sputum samples - 2 consecutive negative samples means the infection has cleared
What is the treatment for drug resistant TB (to isoniazid and rifampin)?
Levofloxacin + bedaquiline + linezolid
What is the treatment for TB resistant to isoniazid, rifampin, fluoroquinolones and aminoglcyosides ?
Prolonged intensive and continuation treatment:
Five drugs - susceptible first-line drugs, fluoroquinolone, bedaquiline, linezolid and additional oral agents
New alternative is bedaquiline, pretonamid and linezolid
Complications of TB?
Pulmonary - pneumothorax, hadmoptysis, pulmonary destruction, fistula, tracheobronchial stenosis, malignancy, chronic pulmonary aspergillosis
Military TB
Septic shock
What type of bacteria is M. tuberculosis?
Gram-positive acid-fast bacilli
