Tuberculosis Flashcards
What is Tuberculosis?
Mycobacterial infection caused by Mycobacteria tuberculosis complex/Koch’s bacillus that mostly affects the lungs
What is Latent Tuberculosis Infection (LTBI)?
Individual infected with M. tuberculosis complex but doesn’t have active TB and is not contagious
What is the leading global cause of death due to infection by a single pathogen?
Tuberculosis
In which groups is the highest incidence of TB found?
Ethnic minority groups
What are some social risk factors for TB?
- Incarceration facilities
- Poverty
- Overcrowding
- Homelessness
What are some medical risk factors for TB?
- Immunodeficiency (HIV, AIDS)
- Excessive alcohol
- Tobacco smoking
- Drugs
- Malignancies
- Diabetes
- End-stage renal disease
How is TB transmitted?
Through aerosol droplets which can stay in the air for several hours
What happens during the primary infection of TB?
M. tuberculosis is inhaled and engulfed by alveolar macrophages, but the pathogen destroys macrophages and causes pneumonitis
What is the Ghon complex?
Radiographic finding for pulmonary TB
What is the Ranke complex?
Later manifestation of Ghon complex
What is the immune response to TB infection?
An immune cascade forms granulomas to contain pathogens, maintaining latency
What is the incubation period for Latent Tuberculosis Infection?
Ranges from a few weeks up to 2 years
What typically triggers the activation of LTBI?
Another infection or medical conditions that cause immunosuppression
What happens when M. tuberculosis multiplies and breaks out of granulomas?
Free pathogens travel via lymphatic vessels to regional lymph nodes
How can pathogens spread from lymph nodes to other organs?
Hematogenously
Which organs can be affected by the spread of TB pathogens?
- Kidneys
- Long bones
- Vertebrae
- Brain
- Meninges
- Eyes
What are the two types of TB presentations?
Pulmonary TB and extrapulmonary TB.
What is the most common symptom of pulmonary TB?
Productive cough, sometimes with haemoptysis.
What are additional symptoms of pulmonary TB?
Pleuritic chest pain, malaise, drenching night sweats, fever, weight loss.
What are the symptoms of extrapulmonary TB?
Organ-specific symptoms.
What is the primary aim of TB investigation?
To distinguish active and latent TB.
What histological finding is associated with TB?
Caseating granulomas.
What are the two main lab tests to diagnose exposure to TB?
Tuberculin skin test (TST) and Interferon Gamma Release Assay (IGRA).
What is the Tuberculin skin test (TST)?
An intradermal injection of tuberculin that induces a delayed hypersensitivity reaction.
Result is measured by the diameter of erythema circling induration 48-72 hours after injection.
What is the Interferon Gamma Release Assay (IGRA)?
A blood test that measures T-cell release of interferon-y in response to TB-specific antigens.
Example: Quantiferon-TB.
What are the gold standard lab tests for diagnosing active TB?
Smear test and Nucleic acid amplification testing (NAAT).
What does the smear test involve?
Three sputum specimens collected 8 to 24 hours apart for acid-fast bacilli (AFB) smears and cultures.
Latent TB cultures and smears are negative, but active TB are positive.
What is the purpose of Nucleic acid amplification testing (NAAT)?
To aid in the detection of M. tuberculosis genetic material using sputum culture.
Used if smear test is inconclusive.
What is the diagnosis if both smear test and NAAT are positive?
Active pulmonary TB.
Where does TB primarily affect in the lungs?
Upper lobe.
What tests should be performed for active extrapulmonary TB?
AFB smear microscopy, culture, NAAT, and histopathology on affected tissues and fluids.
What is the management for TB?
Antitubercular drugs.
What is the treatment for latent TB?
3 months of isoniazid and rifampicin or 6 months of isoniazid.
Better for HIV and transplant patients.
What is the treatment for single drug-resistant TB?
4-drug therapy with different combinations of RIPE.
What is the treatment for multidrug resistant TB?
At least 6-drug therapy.
What is the standard treatment for active TB?
2 months of RIPE followed by a 4-10 months continuation phase with rifampicin and isoniazid.
What is Directly Observed Treatment?
A method to ensure patients take their medications.
