Tuberculosis Flashcards
What causes Tuberculosis?
Certain species of Mycobacterium including:
Mycobacterium Tuberculosis
Mycobacterium Bovine
How is it transmitted?
M Tuberculosis is transmitted by droplet transmission from infected sneezes/coughs
M Bovine transmitted by infected milk and deposited in the cervical/intestinal lymph nodes
What stain is used for a TB smear?
A Ziehl Neissen (ZN) stain, because its an Acid-Fast Organism and so impenetrable to acid based stains.
How does primary TB progress?
Mycobacteria proliferate in alveoli
- > Th1 cells activate macrophages and leads to accumulation of macrophages, epithelioid cells and langhans giant cells.
- > Forms a granuloma and central caseating necrosis begins. (Ghan Focus)
- > Spreads to Hilar Lymph Nodes (Ghan Complex) -> Blood -> All Organs
When do most primary TB infections heal?
85% stop at the point of Ghan Complex (Granuloma with central caseating necrosis and infected hilar nodes)
May calcify as it heals
What are the 3 possible outcomes of a primary TB infection?
Progressive Disease
Latent Disease
Cured Disease
What are the symptoms of primary TB?
Usually Asymptomatic
Maybe: Fever - Malaise - Erythema Nodosum - Chest Signs
How long does latent TB take to cause symptoms and what tissues does it affect?
Pulmonary & Skeletal takes 1-5 yrs but up to 40.
Genitourinary & Cutaneous takes 10-15 yrs but up to 40
Can affect virtually any tissue though
How does progressive pulmonary TB….progress?
The primary focus enlarges & cavitates
Hilar Nodes compress bronchi -> Lobar Collapse
Hilar Nodes discharge into bronchi -> Tuberculous Bronchopneumonia
What other forms of pulmonary TB can develop & how long do they take?
Miliary TB = Widespread small granulomas - appears like fine mottling on CXR
Meningeal TB = High protein & lymphoctyte CSF - v.bad
Tuberculous Pleural Effusion
Takes 6-12 months
What do we look for in a TB Past Medical & drug history?
Well for starters…TB
Diabetes
Any immunosupressant disease e.g. HIV
Immunosupressant drugs e.g. corticosteroids
What do we look fo in a TB social history?
Alcohol IVDA Poor social circumstances Immigration or travel from high incidence area Adolescent, child or elderly
What are the symptoms/signs of pulmonary TB?
Crackles - Bronchial Breathing - Clubbing
Cough - Sputum - Haemoptysis - Pleuritic Pain - Dyspnoea - Malaise - Fever - Weight Loss - Night Sweats
What investigations are there for TB?
Sputum Specimens Chest XR Chest CT Broncoscopy with Bronchoalveolar lavage Pleural aspiration & biopsy HIV test
How do we use sputum specimens to diagnose TB?
3 positive specimens on successive days
Can be by smear (ZN stain since AAFB), Cultures (8 wks) and PCR.
How does pulmonary TB appear on a CXR?
- > Patchy shadowing, usually on upper lobe or apex as aerobic and those areas are better ventilated, often bilateral.
- > Calcification if chronic or healed
- > Cavitation if advanced
What tests can we do on fluid and biopsy from a tuberculous pleural effusion?
Fluid - cytology and smear/culture
Biopsy - Histology & culture
How is TB treated?
By a specialist you must legally notify, with multi-drug therapy (to prevent drug resistance arising)
2 months of 4 drugs then 4 months of 2 drugs
Rifampicin + Isoniazid (+ Ethambutol + Pyrazinamide)
What are the side effects of rifampicin?
Orange urine and tears
Hepatitis
Induces some liver enzymes so prednisalone, oral contraceptives and anticonvulsants are ineffective
What are the side effects of Isoniazid?
Hepatitis
Peripheral Neuropathy
What are the side effects of Ethambutol?
Optic Neuropathy
What are the side effects of Pyrazinamide?
Gout
At what point in treatment does TB stop being infectious?
Two weeks
Who do we screen for TB?
We screen household and close contacts of a sufferer, if theyre positive we move on to casual contacts.
How do we screen for TB?
Young people with no BCG:
- Mantoux or Heaf test using tuberculin to check for immunity.
- If +ve follow with CXR
- If abnormal treat as TB, if normal use chemoprophylaxis with rifampicin
People with a BCG:
- CXR
- If abnormal treat as TB, If normal send home
