Tuberculosis Flashcards
Breifly describe the impact of COVID-19 on Global TB control-
- Resources diverted to focusing on COVID meaning reduced access to diagnosis and treatment services
- Loss of employment and livelihoods aggravating poverty which is a major risk for TB
Why have we failed at treating TB?
- Poverty,
- Health systems,
- HIV
Describe the pathogenesis of tuberculosis
Transmission, primary infection, then latent infection and then active disease.
What are the risk factors for TB?
HIV, TNF alpha, interferon gamma, vitamin deficiency and immune immaturity.
What are some factors that influence a high probability of infection?
Very large number of infecting bacilli, a very long exposure and a very poor immune system
What are the two methods of diagnosing tuberculosis?
Tuberculin Skin Test (TST) and an interferon gamma release Assay (IGRA)
Describe features of pulmonary tuberculosis
- Sputum smear positive PTB patients cause majority of transmission. Symptoms include:
- Cough of 2-3 weeks which is not responding to antibiotics,
- Sputum production (+/- haemoptysis),
- Fever,
- Night sweats,
- Weight loss
What are some of the features of sputum cultures?
It is expensive, slow and biohazardous but gives an additional 20-30% diagnostic yield
Name some of the molecular tests for tuberculosis
GeneXpert and Tuberculosis Molecular Bacterial Load Assav (TB-MBLA) which can measure live cells
Describe the appearances of Primary TB on an X-ray
Ghon Complex - Small, often calcified focus of pulmonary infection and associated lymphadenopathy
Describe how secondary TB can be seen on X-ray
Cavitation - almost always secondary disease.
Miliary TB - Can be primary or post-primary disease
What are some of the current first-line anti-TB drugs?
- Rifampicin,
- Isoniazid,
- Pyrazinamide,
- Ethambutol.
These drugs are used in the intensive phase (2 months) of treatment. R and I are used in the continuation phase (4 months) of treatment
What are some of the disadvantages of the first-line anti-TB drugs?
R - Hepatotoxicity and drug interactions (steroids and opiates)
I - Hepatotoxicity and peripheral neuropathy,
P - Hepatotoxicity and joint pain,
E - Ocular toxicity
How does antibiotic resistance develop?
Naturally occuring M. tuberculosis mutations occur which means resistant organisms are selected by antibiotic therapy (kills of normal bacterium leaving the resistant ones left)
What drugs usually have the greatest resistance and what mutations cause this?
Isoniazid (most common) due to katG and inhA mutations.
The second is Rifampicin due to rpoB mutations
