Tuberculosis Flashcards
How widely spread is TB in the world?
TB kills nore than HIV and Malaria combined.
2/3 of all TB cases are found within 8 countries
~2 billion people are infected world wide
Has there been any changes in the prevelance of TB?
The incidence rate if fallling by about 2% per year.
What are the 8 countries in which TB is the most prevalent?
India (27%- the highest rate) China, Indonesia, the Philippines, Pakistan, Nigeria, Bangladesh and South Africa.
What is the data for the UK like?
The prevalence in the UK is not that high, as children are routinely vaccinated for TB now, however if you live in the UK but was born abroad (and your family is from abroad) you are 15 times more likely to get TB)#
The majority of cases in the UK are people who were born in other counrties or their family is from another country.
Who are the vulnerable groups in the UK?
Those from high prevalence countries HIV positive Immunosuppressed Elderly Neonates Diabetics
What mircoorganisms cause TB?
M. tuberculosis
M.africanum
M.bovis (bovine TB)
What do we know about the mycobacteria that cause TB?
non-motile
Very slow growing
Aerobic (this is why TB is usually found in the apices of the lungs)
Has a very thick fatty cell wall
What function does the thick fatty cell wall of TB mycobacteria serve?
Acid, alkali and detergent resistance
Resistance to destruction by neutophil and macrophage
(They are acid and alcohol fast bacilli)
How is TB transmitted?
It is airborne, it spreads by being attached to aerosol droplets whihc can remain suspended in air for hours.
It usually required prolonged close contact with an infected person to get TB. (if someone does not have pulmonary TB then they can’t spread it through droplets)
Outdoors mycobacteria are eliminated by UV radiation and diluted by the air.
(Bovine TB is an exception and is contracted by drinking infected unpasteurized milk)
What occurs in the primary infection of TB?
Myocobacteria spread to draining hilar lymph nodes, via the lymphatics system.
In the majority (>85%) a primary complex is formed (the inital lesion and a local lymph node), this heals, sometimes without a scar.
Sometimes the primary complex will calcify (Ghon focus + complex0
In the primary infection the development of immunity to the tuberculoprotein has formed.
What are the symptoms usually associated with primary TB infection?
Generally no symptoms but can be fever and malaise.
What are the three outcomes of primary infection?
Progressive disease
Contained latent disease
Cured/cleared
What mechanisms allow post-primary disease to occur?
The bacteria enter a dormant stage.
The rate of replication and destruction (by the immune system) of the bacteria is balanced.
What are some of the forms of progressive disease that can occur after primary infection?
(1% of cases) Tuberculous bronchopneumonia. This involves a continued enlargement and cavitation. The enlarged hilar node compresses on bronchi and can cause lobar collapse. Lymph node discharges in to bronchus. (This has a very poor prognosis)
(1-3%) Miliary TB- haematogenous (via blood) spread of bacteria to multiple organs. Shows up as fine mottling (millet seed shapes) and wide spread granulomas on the x-ray.
What are signs/symptoms that a patient will present with?
Fever
Sweats (mainly at night)
Weightloss
(Cough only if they have pulmonary TB)
