Tuberculosis Flashcards
What is the most significantly fatal infectious disease?
TB
name the 8 countries responsible for 2/3 of global cases
India (27%), China (9%), The Philippines (6%), Pakistan (5%), Nigeria (4%), Bangladesh (4%) and South Africa (3%).
How many people worldwide are infected with TB (approximately)
2 billion
Where in the UK is the highest burden of TB?
London
Why is the incidence of TB so high in London?
due the number of immigrants from high incidence regions
How many cases of TB are seen in NHS grampian each year?
Around 30
What bacterium is responsible for TB?
Mycobacterium tuberculosis
What does mycobacterium leprae cause?
Leprosy
Are mycobacterium aerobic or anaerobic?
Aerobic
Where in the lungs to mycobacterium like to live?
In the apices
Describe the unique feature of mycobacteria
Mycobacterium have a very thick, fatty cell wall which makes it resistant to acids, alkalis and detergents (acid and alcohol fast) and resistant to neutrophil and macrophage destruction
What special stain is used to identify mycobacterium?
Zn
How is TB spread?
Mycobacterium tuberculosis is spread through airborne transmission M. Bovis is spread through the consumption of unpasteurised cows milk
Can TB be spread by; • Shaking hands • Sharing food • Touching surfaces • Sharing toothbrushes • Kissing
No
Describe the infective process that occurs in Tb
- TB bacteria enters the alveoli
- Macrophages recognise the TB and ingest it
- T helper cells are activated and travel from the lymph nodes to the site. The T-helper cells secrete interferon gamma and other cytokines
- Macrophages develop into epithelioid cells and Langerhans’s giant cells and create a granuloma
- The granuloma becomes centrally necrotised over time
Do patients with a primary TB infection usually exhibit chest symptoms?
No
Symptoms in primary TB infections are rare but can occur. What are these symptoms?
fever, malaise & erythema nodosum
What is a Ghon focus & a Ghon complex (seen in primary complex TB infections)?
Calcified initial TB lesions/ lymph nodes
What are the three potential outcomes of a TB infection?
- Progressive disease
- Contained latent disease
- Cleared/cured
What is the next step in TB which is referred to as “progressive disease”?
Bronchopneumonia (enlargement of the primary focus and enlarged hilarity lymph nodes compress bronchi leading to lobar collapse and the enlarged lymph node discharging into the bronchus) or Miliar TB (spread of seed like TB lesions to multiple organs in the body)
What is post primary disease? Explain how post primary disease occurs.
Post primary disease is “latent” TB
There are two main hypotheses which explain how this happens;
- TB bacteria entering a dormant stage with low or no replication over prolonged periods of time
- Balanced state of replication and destruction by immune mechanisms
What are the classic clinical features of TB?
- Cough
- Fever
- Night Sweats
- Weight loss
What is the most useful diagnostic tool for TB?
CXR
What will primary TB look like on a CXR?
Pneumonic lesion accompanied by enlarged hilar nodes
How many sputum samples should be taken from a suspected TB patient?
3 (8-24hrs gap, at least 1 early morning sample)
List the 4 drugs that can be used in TB and their side effects
- Isoniazid (hepatitis and peripheral neuropathy but these symptoms can be mitigated with via B6 supplements)
- Pyrazinamide (hepatitis and gout)
- Rifampicin (hepatitis, makes hormonal contraception ineffective, induces liver enzymes)
- Ethambutol (optic neuropathy)
Why must multiple drugs be used to treat TB?
Single drug treatments will lead to resistance within 14 days
How long must TB therapy be continued for?
6 months or longer
What is the 4:2/2:4 rule for treating TB?
4 drugs for 2 months then drop down to 2 drugs for 4 months
Who should be screened for TB?
Contacts of people with active pulmonary or laryngeal TB who are aged ≤65 years
How is latent TB treated?
- Rifampicin & Isoniazid for three months, or
- Isoniazid only for six months ,or
- Rifampicin only for six months, or
- Rifapentine & Isoniazide once weekly for 12 weeks (underserved population)
