Tuberculosis Flashcards
Describe the global distribution of TB
Global disease burden is falling
- Incidence rate falling at 2% per year
- TB deaths have fallen by 29% since 2000
Where in UK is TB most prevalent?
London
- Due to immigration from high incidence areas
- 39% all UK cases are London
How is TB transmitted?
Airborne
- Can stay in the air for many hours, more if poor circulation
- Usually require close prolonged contact (>8 hours)
Why is TB less transmissible outside?
Outside mycobacteria are eliminated by UV radiation and dilution
Describe the T-cell immune response to TB
- Activated macrophages -> epithelioid cells -> Langhan’s giant cells
- Accumulation of macrophages, epithelioid and langhan’s cells —»> GRANULOMA
- Central caseating necrosis
Describe primary TB
Small infection
Cleared/cured
Contained latent
What is the progression from primary TB to bronchopneumonia?
Primary focus continues to enlarge - cavitation
Enlarged hilar lymph node discharges into bronchi, lobar collapse
Enlarged lymph node discharges into bronchus
Poor prognosis
Explain Miliary TB
Hematogenous spread of bacteria to multiple organs
Fine mottling on X-ray, widespread granulomata
CNS TB in 10-30%
What are the possible progressions of TB from primary complex?
Progressive primary disease (1%)
Miliary, meningeal, pleural TB
Post primary disease
- Pulmonary, skeletal
Genitourinary, cutaneous TB
What mycobacteria can cause TB?
M.turberculosis
M.africanum
M.bovis
What type of bacteria casue TB?
Aerobic
Non motile bacillus, slow growing (disease is slow and treatment long)
Has a think fatty cell wall
What are the TB causing bacteria resistant to?
Acids, alkalis and detergents
Neutrophils and macrophage destruction
What is the common clinical presentation of TB?
Triad of symtpoms
- Prolonged cough (>1month)
- Night sweats
- Weight loss
And fever
What would you expect to see on a chest X-ray?
Classical signs
- Apices are soft/fluffy/nodular upper zones
- Cavitation in 20-30%
Lymphadenopathy is rare
CXR is normal in 13% definitive TB patients
When do you consider a CT scan?
Normal CXR but clinical suspicion
Miliary TB
Cavitation and other differential
Lymphadenopathy, alternative diagnosis
Targets for BAL
How do you confirm a diagnosis?
Sputum sample
Bronchoscopy with BAL
Endobronchial ultrasound (EBUS) with biopsy
Urine in urogenital TB
Lumbar puncture in CNS TB
Aspirate/biopsy from tissue (lymph-node, bone, joint, brain, abscess …)
Mantoux or IGRA are not routinely used in diagnosis of active TB
What are the 4 standard drugs used to treat TB?
Isoniazid
Pyrazinamide
Rifampicin
Ethambutol
What are the side effects of isoniazid?
Hepatitis
Peripheral neuropathy
What are the side effects of pyrazinamide?
Hepatitis
Gout
What are the side effects of rifampicin?
Orange (irn bru) urine/tears/lenses
Induces live enzymes, prednisolone, anticonvulsants
All hormonal contraceptive methods are ineffective
Hepatis
What are the side effects of ethambutol?
Optic neuropathy
(must check visual activity)
What is the treatment process for TB?
4 drugs for 6 moths
Multidrug is essential - single agent treatment leads to drug resistant organisms within 14 days
Legal requirement to notify all cases and trace contacts
Test for Hepatitis B&C and HIV
What other drugs must you take alongside treatment?
Pyridoxine (vit B) with isoniazid to reduce risk of neuropathy
Steroids (CNS, miliary and pericardial)
Vitamin D substitution
Who gets TB screening?
Contacts of people with active pulmonary or laryngeal TB aged <65
New entrants from high endemic areas
Pre-biologics
Outbreaks
What is a LTBI diagnosis?
Asymptomatic
Normal CXR
Normal examination
Positive Mantoux skin test or IGRA test
How do you treat LTBI?
Rifampicin and isoniazid for 3 months OR
- Isoniazid only for 6 moths
- Rifampicin only for 6 moths
- Rifampicin and Isoniazid once weekly for 12 weeks
