Tuberculosis Flashcards
What is TB caused by?
The bacteria mycobacterium tuberculosis
Describe the characteristics of the causative agent of TB?
Gram positive bacillus
Acid fast
Slow growing
What type of hypersensitivity does TB cause?
Type IV
How is TB transmitted?
Aerosol route
Some who come into contact with TB will not contract the disease, some will and some will have latent TB and be affected later in life
What is a Ghon complex?
The combination of a Ghon focus (small lung lesion composed of macrophages) and hilar lymph nodes
What is the pathophysiology of primary TB
- Primary infection of the lungs
- Ghon focus and Ghon complex forms
- Granuloma forms
- Caseous necrosis occurs
What is a granuloma?
A collection of epithelioid histiocytes
What is the difference between primary and secondary TB?
Primary is when you get it for the first time
Secondary is when an initial infection is reactivated
Where does secondary TB usually occur?
Apex of lungs
May spread locally or to distant sites
What causes secondary TB?
Immunosuppression (drugs like steroids, HIV)
Malnutrition
Where outside of the lungs can TB affect?
CNS
Vertebral bodies (Pott’s disease)
Renal
GI tract
What ages tend to present with TB?
Very young children, young adults and the elderly
What are the high risk groups for TB?
Deprived areas
Immigrants or foreign travel from Asia, Latin America, Eastern Europe or Africa
Immunosuppressed
Silicosis and apical fibrosis
What is the majority of TB disease?
Re-activated disease in individuals previously entering the country with latent TB infection
What are the symptoms ofTB?
Persistent productive cough Haemoptysis Pleuritic chest pain Hoarseness Upper zone crackles Night sweats Fever Weight loss
What can present similarly to TB?
Community acquired pneumonia
Lung cancer
What is the key TB investigation, and what result indicates TB?
Ziehl Neilson stain - acid fast bacilli turn bright red
What investigations are done for TB?
CXR Ziehl Neilson stain Sputum culture FBC Nucleic acid amplification tests
What is a skin test?
Used for screening - can tell you whether the patients has latent TB
What is the phrase to remember the treatment for TB?
4 for 2, 2 for 4
What is the treatment for active TB?
4 for 2 Rifampicin Isoniazid Pyrazinamide Ethambutol
Then 2 for 4
Rifampicin and isoniazid
What is the treatment for latent TB?
2 for 4
Rifampicin
Isoniazid
What is the mechanism of action for rifampicin?
Antibiotic - prevents the transcription of bacterial DNA into mRNA
What is the main side effect of rifampicin?
Orange fluids
What is the main side effect of isoniazid?
Peripheral neuropathy (e.g. pins and needles, loss of feeling in peripheries)
What is the main side effect of pyrazinamide?
Joint pain
What is the main side effect of ethambutol?
Colour blindness
When does TB treatment need altering?
Dose of ethambutol needs adjusting in patients with renal impairment
Which vaccine offers protection against TB?
The BCG vaccine
Who is the TB vaccine given to?
High risk infants
Previously unvaccinated TB-negative contacts of TB cases
Healthcare workers and others who work with high risk groups
What does the TB vaccine contain?
Live attenuated virus
