PBL 6 - Tuberculosis Flashcards
(35 cards)
How does tuberculosis normally spread? (1 mark)
Mainly by inhalation of infected airborne aerosol (air containing water droplets containing m.
tuberculosis). (
Which organs are normally first infected by tuberculosis, and why is this? (1 mark)
The lungs (1/2 mark). M.tuberculosis prefers a high level of oxygen to grow and the lungs provide this (1/2 mark)
Explain carefully why tuberculosis is difficult to treat with drugs (1 mark)
M. tuberculosis is intracellular (1/2 mark) and has a waxy cell wall that resists penetration by drugs
(1/2 mark). Antibiotics have to penetrate both the host mammalian cell and the bacterial cell wall to
be effective .
What is usually the first symptom of pulmonary tuberculosis? (1 mark). List four other
signs/symptoms that may present. (2 marks)
First symptom: Productive cough (1 mark)
Other symptoms: Night sweats, Weight loss, Loss of appetite, Haemoptysis, (coughing up blood)
Chronic fatigue, (Any four 1/2 mark each)
Give four separate methods used for the diagnosis of tuberculosis (2 marks)
Four from : PCR (polymerase chain reaction) (from sputum) Skin test (Mantoux/Pirquet) Chest Xray
Histological examination of biopsy Microbiological culture (sputum) Any four (1/2 mark each)
What four drugs make up the normal first line treatment protocol for tuberculosis? (2 marks)
Rifampicin, Isoniazid, Pyrazinamide, ethambutol (1/2 each) (RIPE)
What parts of the body can TB also infect? (2)
lymph
nodes, bones and joints, kidneys, brain, gut, the skin
(extra-pulmonary and non infectious)
Why are mycobacteria named acid-fast bacilli? (1)
resistance to decoloration with acid washing;
How long does it usually take to culture mycobacteria? (1)
2-6 weeks
What is the pathophysiology of TB? (3)
o Primary infection – engulfed by macrophages, forms granulomas – asymptomatic
o Latent infection – bacteria dormant for months-years
o Secondary infection – reactivation of bacteria, usually in lung apex causing symptoms e.g immunosuppressed (APEX as most oxygenated)
What percentage of the population have TB? (1)
1/3rd of population
How do you do the Mantoux skin test? (2)
Inject Tuberculin intradermally, measure cell mediated response
5mm pos in – HIV positive, old healed TB, recent TB contact
10mm pos in – Injection drug users, high risk setting, recent arrivals
15mm pos in – No TB risk factors
What is the BCG vaccine? Why might this give a false positive on mantoux test? (2)
Vaccine prevent against TB
antibodies to TB still present.
What are features of a chest X-ray you would see in someone with TB? (2)
Apical consolidation, bilateral opacities/calcification/cavitation
Hilar shadowing
What would you detect in a sputum test? (1)
Detect bacteria
or fungi
Why would you take a histological examination of biopsy specimens in TB (2)
Multinucleate Langerhans giant cells, AFBs inside macrophages
takes a long time for microbiology
In extra-pulmonary TB - Culture can be negative
Risk factors for TB (2)
Close contact Ethnic minorities Alcoholics HIV positive Young and elderly Homeless
What drug must you not take if you are taking rifampicin? (1)
Oral contraceptives
as acts on liver, may not work
What are possible side effects of the TB treatment (3)
Rifampicin = Liver enzymes, orange secretions, hepatotoxicity in pregnancy
Isoniazid = Peripheral neuropathy, hepatotoxic
Ethambutol = Optic neuritis leading to red-green colour blindness
(Liver problems, vision changes, neuropathy)
What is MDR-TB? (2)
Multi-drug resistant TB
- Resistant to isoniazid and rifampicin- MDR-TB
- Must take streptomycin, amikacin, levofloxacin
What is the relationship between TB and HIV? (2)
TB and HIV infection act synergistically, each
condition exacerbating the other
Reactivation is higher if you have TB
How is TB prevented in the UK (3)
o Contact tracing and screening
= Detect source of infection, vaccinate, offer mantoux test to people close to those with TB
BCG Vaccine – given to schoolchildren at around 12/13 years of age + High risk groups
Identifying and treating all those with TB
What is CCDC? (1)
Consultant in Communicable Disease Control
What is Sputum
Sputum is a thick fluid produced in the lungs and in
the adjacent airways
