Pathology of Tuberculosis (TB): Part 1 - aetiology, risks and diagnosis & Signs and symptoms Flashcards
aetiology
what bacterium causes TB in majority of cases
- Mycobacterium tuberculosis
what does mycobacterium tuberculosis being an obligate aerobe mean and what does this means for the lungs?
- means it likes oxygen rich environments
- lungs is ideal place for growth for this bacterium
What are the 2 MAIN ways can Mycobacterium tuberulosis be spread
- airborne droplets
- dust microbe particles
what are 5 features of Mycobacterium tuberculosis
- acid fast
- slow rate of growth
- sensitive to heat and UV radiation
- non-motile
- likes highly oxygenated tissue (obligate aerobe)
what was mycobacterium tuberculosis first identified?
first identified in 1882
why does M. Tuberculosis have a slow rate of growth and what does this mean for diagnosis?
- Slow rate of growth due to lipid coat
- makes diagnosis by culturing difficult
risk factors
what are 2 categories for people who are at high risk for developing TB
- people who have been recently infected with TB bacteria
- people with medical conditions that weaken the immune system
what are 5 ways higher incident rates can occur due to people who were recently infected with TB bacteria
- close contact with people with TB disease
- people who migrated from areas of the world with high TB rates
- children less than 5 years of age who have a positive TB test
- groups with high rates of TB like homeless persons and persons with HIV infection
- persons who work or reside with people who are at high risk of TB in facilities like hospitals and homeless shelters.
outline 9 medical conditions/diseases that cause a weakened immune system which can increase incidence of TB
- Substance abuse
- Silicosis
- Diabetes mellitus
- Severe kidney disease
- Low body weight
- Medical treatments such as corticosteroids or organ transplant
- Infection with HIV
- Head or neck cancer, leukaemia, or
Hodgkin’s due to it being metastising - being a baby or young as they have weaker immune systems usually
what are 2 other bacteriums that can cause TB disease
- M. bovis (from unpasteurised cow milk)
- M. africanum
write out 5 characteristics of latent TB infection
- no signs or symptoms
- host defences prevent growth of bacteria
- not infectious and cannot pass infection on
- skin or blood test might be postive for the bacteria
- normal chest X-ray
Outline out 6 characteristics of TB disease (Active TB)
- primary infection/activation of latent TB
- signs and symptoms/patient feels sick
- CAN spread infection
- skin or blood test positive
- may have abnormal chest X-ray or sputum sample
- requires treatment to resolve
diagnosis
what are 5 ways you can test and diagnosis TB?
- skin test
- microbiological sampling
- blood test
- molecular testing
- imaging
outline 3 steps for how the tuberculin skin test works
- 0.1ml of tuberculin derived protein is injected into skin of forearm
- wait 72 hours
- measure diameter of palpable, raised hardened area/swelling (Not an erythema)
what are the 2 names for the TB skin test
- tuberculin skin test
OR - Mantoux test
