TB Flashcards
What is the causative agent of Tuberculosis (TB)?
Mycobacterium tuberculosis, a slow-dividing, rod-shaped, acid-fast bacillus.
Why are Mycobacterium tuberculosis bacteria called ‘acid-fast bacilli’?
They have a waxy coating that makes them resistant to the acids used in standard gram staining. Special staining, such as Ziehl-Neelsen, is used, which stains them bright red.
What is Multidrug-resistant TB (MDR-TB)?
MDR-TB is a strain of M. tuberculosis that is resistant to more than one TB drug, such as isoniazid and rifampicin, making it harder to treat.
How is tuberculosis most commonly spread?
TB is primarily spread by inhaling saliva droplets from infected individuals.
What are the possible outcomes after M. tuberculosis enters the body?
- Immediate clearance (most cases)
- Primary active tuberculosis (active infection after exposure)
- Latent tuberculosis (no symptoms, not contagious)
- Secondary tuberculosis (reactivation of latent TB)
- Miliary tuberculosis (severe, disseminated TB)
What is latent tuberculosis?
It is the presence of M. tuberculosis in the body without symptoms or contagiousness, usually encapsulated by the immune system. Reactivation can occur if the immune system is weakened.
What are the extrapulmonary sites where TB can spread?
- Lymph nodes
- Pleura
- CNS (Central nervous system)
- Pericardium
- Gastrointestinal system
- Genitourinary system
- Bones and joints
- Skin (cutaneous tuberculosis)
What is a cold abscess in tuberculosis?
A firm, painless abscess, usually in the neck, caused by TB, with no typical inflammation, redness, or pain.
Who are at higher risk for tuberculosis?
- Close contact with active TB
- Immigrants from high-prevalence areas
- Immunocompromised individuals (e.g., HIV patients)
- Malnutrition, homelessness, drug users, smokers, alcoholics
What is the BCG vaccine, and who is it given to?
The Bacillus Calmette–Guérin (BCG) vaccine is an intradermal injection of live attenuated Mycobacterium bovis that provides immunity against M. tuberculosis. It is given to those at higher risk, including healthcare workers and people from high-prevalence areas.
What are the typical symptoms of tuberculosis?
- Cough
- Haemoptysis (coughing up blood)
- Lethargy
- Fever or night sweats
- Weight loss
- Lymphadenopathy
- Erythema nodosum (red nodules on the shins)
- Spinal pain (Pott’s disease)
What is the Mantoux test used for in tuberculosis?
The Mantoux test involves injecting tuberculin into the skin and measuring the skin’s induration (swelling) after 72 hours. It tests for immune response to M. tuberculosis infection.
How does a chest X-ray help in diagnosing tuberculosis?
- Primary TB may show patchy consolidation, pleural effusions, or hilar lymphadenopathy.
- Reactivated TB shows consolidation with cavitation, usually in upper lung zones.
- Miliary TB appears as ‘millet seed’-like nodules scattered across the lungs.
What is the RIPE mnemonic for TB treatment?
- R - Rifampicin (6 months)
- I - Isoniazid (6 months)
- P - Pyrazinamide (2 months)
- E - Ethambutol (2 months)
What is the common side effect of Isoniazid?
Peripheral neuropathy, which can be prevented by co-prescribing pyridoxine (vitamin B6).
What are some common side effects of TB treatment drugs?
- Rifampicin: Red/orange discolouration of secretions, liver enzyme induction (reduces effectiveness of drugs like the combined contraceptive pill)
- Isoniazid: Peripheral neuropathy, treated with pyridoxine (vitamin B6)
- Pyrazinamide: Hyperuricaemia, leading to gout or kidney stones
- Ethambutol: Colour blindness and reduced visual acuity
How should a patient with active TB be isolated in a hospital?
They should be placed in a negative pressure room to prevent airborne spread of TB.
What test can be used to detect drug resistance in TB?
Nucleic Acid Amplification Tests (NAAT), which detect the DNA of M. tuberculosis and provide faster results than traditional cultures.
