Tuberculosis Flashcards
Mycobacteria
Organism responsible for TB
Ubiquitous in the soil/water
Evolved to avoid cell mediated destruction (resistant to amoebae
Non motile bacillus
Very slow growing
Aerobic (predilection for apices of the lungs)
Very thick cell wall - resistant to acids, alkalis, detergents, neutrophil and macrophage destruction
Tuberculosis bacteria
Mycobacterium tuberculosis
M. bovis (bovine TB)
Transmission of TB
When the bacteria reach the alveoli, the disease proliferates (otherwise is caught in nose/coughed out)
From “open” pulmonary TB, coughing/sneezing
Inhaled
Bovine TB - from drinking cows’ milk, deposited in cervical/intestinal nodes
Activated macrophages
Killing the TB causes tissue damage
Susceptible host
Elderly
Malnourished
Resistant host
> 20 years
Healthy diet
Primary infection
No preceding exposure or immunity
Usually children, 80% infected in alveolus
Progressive disease/contained latent/cleared cured
Post primary disease
Reactivation of mycobacterium from primary latent infectiction disseminated throughout the body via the blood stream
New reinfection from outside source, susceptible previously infected host
Clinical symptoms
Cough Sputum Haemoptysis Pleuritic pain Breathlessness Systemically unwell - malaise/weight loss/fever
Investigations
CXR (patchy shadowing, often apices/upper zones, or apex of lower lobes, cavitation if advanced, may calcify if chronic or healed)
Sputum specimens (smear/culture)
CT scan of thorax
Bronchoscopy
Pleural aspiration and biopsy if pleural effusion
Treatment of TB
Multiple drug treatment (always multitreatment)
TB medications
First two months:
Rifampicin (orange urine/tears, hepatitis)
Isoniazid (hepatitis, peripheral neuropathy)
Ethambutol (optic neuropathy)
Pyrazinamide (gout)
Next four months:
Rifampicin
Isoniazid
(Non infectious after two weeks)
