TB Flashcards
What is TB?
An infectious disease of the respiratory tract due to the airborne spread of mycobacterium tuberculosis
It often presents in the upper lung but systemic and circulatory problems can occur and it can spread to other organs
Where is TB common?
Africa, India, the indian subcontinent, China, Aisa and Indionesia
Does TB have an environmental reservoir?
Not that we know of
Where are the cases in Tayside presenting from?
Eastern Europe or Pakistan
What happens after TB exposure?
Describable latent TB.
Tb infects the upper zone of the lungs- latent infection
Travels to the distal alviolus and phagacytosed by alveolar macrophages and dendritic cells
Transendothilial migration leads to the formation of a granuloma. The infection can grow and multiply here
The granuloma walls are very think and if contained the infection remains latent here
What happens during active TB?
If the gramuloma walls break the infection will be released into the lungs
What percentage of those with TB infection will remain well and what is the lifetime risk of tuberculosis for them?
90% will remain well
10% lifetime risk of infection. 5% primary TB and 5% reactivation of latent disease
What are the clinical features of Primary pulmonary TB?
1) Sub acute disease, gradual onset
2) Weight loss, malaise, night swears
3) Cough, haemoptysis, breathlessness
4) Upper zone crackles and tubercles (white dots) and cavity formation
What are the clinical features of meningeal TB?
Headache, drowsy, fits and TB in CSF
What are the clinical features of gastrointestinal TB?
Pain, bowel obstruction, perforation and peritonitis
What are the clinical features of spinal TB?
Pain, deformatity and paraplegia
Antibiotics for 12 months
What are the clinical features of pericardial TB?
Tamponade
What are the clinical features of renal TB?
Renal failure
What are the clinical features of adrenal TB?
Hypoadrenalism
Why should you never inject steroids into a solitary arthritic joint?
It may be septic arthritis caused by TB
What form of TB is lymphadenopathy associated with?
Mediastinal TB
A cold abscess can appear on the chest. What is this a sign of?
Dormant TB- no pain or associated inflammation
How is TB diagnosed?
Culture
PCR- 90% sensitive (can give false positives for current infection and does not give antibiotic sensitivities but rapid)
Zeil Nelson stain- 50% sensitive (Gives infectivity data
What are the advantages and limitations of sputum culture for TB?
Most sensitive but takes time and requires skilled people
What are the advantages and limitations of PCR for TB?
90% sensitive- can give false positives for current infection
Does not give all antibiotic sensitivities. Will show if rifampicin sensitive
Rapid
What are the advantages and limitations of zeil Nelson stain for TB?
50% sensitive
Gives infectivity data- smear positive or smear negative
Rapid and cheap
What does ‘smear positive’ imply?
TB and infectious
What does ‘smear negative, culture positive’ imply?
TB and needs treatment but not infectious
What would you see on a histology slide of someone with TB?
Multinucleating giant cell granulomas
Caseating necrosis
Sometimes visible mycobacterium
What would you see on a CXR of someone with TB?
Upper lobe predominance
Cavity formation and tissue destruction
Scarring and shrinkage
Heals with calcification- often in lymph nodes
What is milliary TB?
Wide spread dissemination of mycobacterium TB via blood stream spread.
Can rapidly be fatal
What are the 4 drugs used to treat smear positive TB?
Rifampicin
Isoniazid
Pyrazinamide
Ethanbutol
If the patient becomes smear negative, what is the step down treatment?
Rifampicin
Isoniazid
What are the side effects of rifampicin?
Colours urine and body fluids orange/pink
Potent inducer of cytochrome enzymes
=> Breakdown of all steroids inc oral contraceptive
=> Breakdown of opiate analgesics
What are the side effects of ethanbutol?
Optic neuritis- inflammation of the optic nerve- must ensure patients are not colour blind before treatment
What are the side effects of izoniazid?
Hepatitis, renal failure and neuropathy
B6 deficiency and given peridoxine
What is DOT and when is it used?
DOT = Directly observed therapy
As compliance is poor you receive your medication at a pharmacy and must be supervised
Used when you suspect medications not being taken
When TB is diagnosed, who must be informed?
Public health for contact tracing
Who must be detained in hospital in an infection control side room?
Anyone who is smear positive
What is single drug resistant TB?
Resistant to izoniazid
What is MDR TB and what are the consequences?
Resistant to izoniazid and rifampcin
Require injectables and 9-12 months of treatment
What is XDR TB and what are the consequences?
Resistant to more than izoniazid and rifampcin
Require injectables and quinalone for 9-12 moths
Must be in a side room in infection control until better
Form eastern Europe/ africa
What happens if your newly Dx HIV positive and TB positive?
Treat viral load first and then TB within 8 weeks
TB can be the first presenting symptom of someone with HIV. True or false?
True
What is defined as latent TB?
Culture negative and symptom free
May have calcifications/ granlomas on the CXR
What can cause reactivation of latent TB?
Steroids and immunosupressive drugs
What are the tests for previous TB exposure?
Tuberculin skin test/Mantoux test
Interferon gamma release assay (blood test)
How does the interferon gamma release assay work?
Blood test which looks for the interferon gamma specific antigen only found in mycobacterium TB
It doesn’t react with BCG which is an attenuated strain of M bovis
How does the mantoux test work?
Intradermal injection of tuberculin- checking for skin reaction.
Delayed type 4 hypersensitivity
Cannot distinguish between latent TB, cured TB, active TB and BCG
How is latent TB treated?
Can be treated or untreated.
Must be treated if you want to give anti-TNF drugs
Treatment = 6 months izoniazid OR 3 months izoniazid and rifampcin
How is TB prevented
Contact tracing and screening of high risk sub groups
Isolation of infectious cases
BCG immunisation- most effective in neonates of high risk families
Social measures- housing and nutrition
Who might you want to give anti-TNF drugs to and therefore need to treat their latent TB?
Anyone with rheumatoid’s, Crohn’s, Psoriasis or ankylosing spondylytis
What is in the BCG vaccine?
Attenuated strain of M bovis
When people are on TB treatment, what should be monitored?
Liver function
Kidney function?
