Flashcards in Tuberculosis. Deck (49):
What is TB?
A chronic mycobacterial infection described in many body sites e.g. Lung, gut, kidney, lymph nodes and skin.
What are the characteristic pathology findings in TB?
Delayed type four hypersensitivity e.g. Granulomas with necrosis.
What is the most common pathogen that causes TB?
What is the second most common pathogen that causes TB that is occasionally seen here?
What is the third most common pathogen that causes TB?
Who do atypical TB infections normally affect?
Why is it important to get a tissue diagnosis of TB and not just a clinical one?
The treatment is long and toxic.
What tests do we do for TB?
CXR, microscopy of body fluids and tissue.
Culture of washings, sputum, pleural effusion etc.
PCR is the primary test.
Microscopy for AAFB.
Liquid culture for mycobacteria.
What is IGRA testing?
Interferon gamma release testing.
Gamma interferon released from circulating T lymphocytes in response to several stimuli is quantified. It can see if patient has lymphocytes primed to respond to MTB.
Tells you if they have latent, past treated or current TB but not which.
Has no cross reaction with BCG.
What do we see on CXR for TB?
Patchy infiltrate mainly in the upper zones. Can see contraction of the upper lobes due to fibrosis pulling the hokum further up than it should be.
What happens in primary TB?
Inhaled organism is phagocytosed and carried to hilar lymph nodes. Immune activation leads to granulomatous response in the nodes and lungs usually killing the organism.
Sometimes the infection is overwhelming and spreads.
What is secondary TB?
Re infection or reactivity on of the disease in a person with some immunity.
Tends to Ramon instillation localised, especially in lung apices.
It can progress to spread by the airways or the blood stream.
What tissue changes do we see in primary TB?
Small goon focus in periphery of mid some of lung.
Large granulomatous hilar nodes.
What tissue changes do we see in secondary TB?
Fibrosing and cavitating apical lesion.
What is an important differential diagnosis of secondary TB?
What causes the disease to reactivate?
Decreased T cell function from: age, other diseases e.g. HIV or immunosuppressants.
May be reinfected at a high dose by a more virulent organism.
Can you be a carrier for TB?
Yes if your immune system keeps it in check.
What are the risk factors for catching TB?
HIV infection, in contact with a smear positive person, having children with a positive head test, immigrants from Africa and Indian subcontinent. Poverty and homelessness.
What are the four anti TB drugs?
Rifampicin. - R
Isoniazid - H
Ethambutol - E
What kind of drugs are the anti TB RIPE drugs?
Quite toxic antibiotics.
What is the treatment for TB with respiratory or non respiratory issues?
HRZ(E) for 2 months and HR for 4 months.
What is the treatment for TB with meningitis or CNS issues?
HRZ(E) for 2 months and HR for 10 months.
What do we try and give all 4 antibiotic drugs as initial treatment for TB?
To identify and cover existing resistances and try and prevent further ones.
What do we use to administer treatment if compliance is a problem?
DOTS directly observed therapy short course.
Responsible observer watches them take it.
How long do we continue HRZE in a hospitalised patient?
In isolation until they are smear negative.
What do we need to administer to someone who also has HIV?
What are the side effects of isoniazid?
What are the side effects of rifampicin?
Febrile reactions/flu syndrome.
What are the side effects of pyrazinozide?
Anorexia and vomiting
What are the side effects of ethambutol?
What is cutaneous hypersensitivity?
The lightest touch hurts.
What does retrolobular neuritis cause?
Causes colour blindness and then full blindness.
When do we stop TB drugs for hepatitis?
When the LFT's are up to 400.
What drug can turn tears and bodily fluids orange?
Do we treat latent TB?
In America but not here.
What is MDR-TB?
Resistant to first line therapy e.g. Isoniazid and rifampicin.
What is XDR- TB?
Resistant to second line treatments e.g. Isoniazid, rifampicin, fluoroquinolones and other injectables.
What are the legal implications of TB?
It's a reportable illness - public health need to know about suspected and confirmed.
Smear positive patients (open TB) are infective and can be detained until they are no longer infective, but they cannot be forced to take treatment.
What is Potts disease of the spine?
TB of the spine, not seen very often but is common in Africa.
When should we suspect TB?
Returning travellers, immunocompromised patients and non resolving pneumonia.
What is a common opportunistic virus that affects the immunocompromised host?
What does mycobacterium tuberculosis look like on culture?
Bread like growth on a lewenstein Jensen medium.
How long does mycobacterium TB take to culture?
Up to 3 months.
What is AAFB?
Acid and alcohol fast bacilli.
Mycobacterium and others have a thick waxy coat that is not affected by acid or alkali. So needs a ziehl neelsen dye ZN.
Appear as red rods under microscopy.
What are the drawbacks of ZN?
Doesn't tell type or antibiotic sensitivity.
Just that patients are infected.
How long does TB PCR take?
What are the pros and cons of TB PCR?
Provides info on species and some antibiotic sensitivity but is expensive.
What is the best test for antibiotic susceptibility of TB?
Culture even though it's slow.