Tuberculosis Flashcards
What is meant by the ‘acid fast’ property of mycobacterium tuberculosis?
Its waxy coating is resistant to the acids used in the staining procedure
What stain is used to identify TB?
Zeihl-Neelsen stain
What type of granuloma is formed in TB?
Caseous
What happens in primary TB
- Exposure to M. tuberculosis
- Small lung lesion known as ‘Ghon focus’ develops in the lungs
- Ghon focus + hilar lymph nodes is known as a Ghon complex
What is active TB?
Active infection in various areas within the body
In the majority of cases the immune system is able to kill and clear the infection
What is latent TB
Immune system encapsulates sites of infection and stop the progression of the disease
What is secondary TB?
When latent TB reactivates
What happens if the immune system is unable to control the TB?
Causes a disseminated, severe disease
Referred to as miliary TB
List 4 Extra-pulmonary TB infections
- CNS (tuberculous meningitis - most serious complication)
- vertebral bodies (Pott’s disease)
- cervical lymph nodes (scrofuloderma)
- renal
- GI tract
What is a “cold abscess”?
A firm painless abscess caused by TB, usually in the neck
NO inflammation, redness or pain as expected
List 4 risk factors for TB
- Contact with active TB
- Immigrants from areas of high TB
- Immunosuppression ie. HIV
- Homeless people or IVDU
What type of vaccine is the BCG?
live attenuated
What 2 things must be checked/assessed prior to the BCG
- Mantoux test
- Immunosuppression and HIV
List 2 groups of people which the BGC is routinely offered too
- Neonates who are born in areas in UK with high rates of TB
- Healthcare workers
Presentation of TB?
- Lethargy
- Fever or night sweats
- Weight loss
- Cough +/- haemoptysis
- Lymphadenopathy
- Erythema nodosum
What is Pott’s disease?
Form of osteoarticular TB which affects the spine, also known as Tuberculous spondylitis?
How does Pott’s disease present?
Typical TB features + Spinal pain
Describe the typical disease pattern of Pott’s disease
- Starts in subchondral bone
- Follows longitudinal ligaments
- Mainly lower thoracic and upper lumbar spine
- Insidious onset over months → may progress to paralysis
List 2 tests to check for Latent TB
- Mantoux test (screening)
- Interferon‑gamma release assay
IGRA is used if there are NO features of active TB but a positive Mantoux test to confirm a diagnosis of latent TB
Explain the Mantoux test
- Tuberculin (TB protein) injected into forearm
- Injecting creates a bleb under the skin
- After 72 hours the induration of the skin at the site of the injection is measured
- Induration of ≥ 5mm is positive
Explain the Interferon-Gamma Release Assays (IGRAs)
Sample of blood mixed with antigens from the TB bacteria
If patient has had previous contact with TB, interferon-gamma is released from WBC
Investigations if active TB is suspected
Highlight gold standard
- Chest xray
- Sputum smear (3 specimens needed)
- Sputum culture (GOLD standard)
- NAAT (diagnosis within 24-48 hours)
When is NAAT used over sputum cultures?
- If having the information would affect treatment OR
- They are at higher risk of developing complications (ie. in HIV)
List 3 ways to collect cultures for suspected TB
- Sputum
- Mycobacterium blood cultures
- Lymph node aspiration or biopsy
List 3 chest X-ray findings of primary TB
- Patchy consolidation
- Pleural effusions
- Hilar lymphadenopathy
Typical chest X-ray finding of reactivated TB
Upper lobe cavitation
What typical chest x-ray finding is seen in Miliary TB?
“Millet seeds” uniformly distributed throughout the lung fields
Management of Latent TB?
- 3 months Isoniazid (with pyridoxine) and rifampicin OR
- 6 months of isoniazid (with pyridoxine)
Management of Acute Pulmonary TB (RIPE)
- Rifampicin for 6 months
- Isoniazid for 6 months
- Pyrazinamide for 2 months
- Ethambutol for 2 months
A patient is started on RIPE, what must be co-prescribed and why?
Pyridoxine
Isoniazid causes peripheral neuropathy, pyridoxine (B6) should be co-prescribed prophylactically
Is TB a notifiable disease?
YES - must inform PHE
If a patient is identified to have active TB, what steps must be taken to prevent airborne spread?
Should be isolated until they are established on treatment (usually 2 weeks)
In hospital negative pressure rooms are used to prevent airborne spread
Treatment of meningeal TB?
Treated for at least 12 months with the addition of steroids
What is Multi drug resistant TB?
TB resistant to isoniazid and rifampicin
S/E of Rifampicin
- Red/orange urine and tears
- Potent inducer of CYP P450 enzymes (important for medications such as the COCP)
S/E of Isoniazid
Peripheral neuropathy
Pyridoxine (B6) usually co-prescribed prophylactically
S/E of Pyrazinamide
Hyperuricaemia resulting in gout
S/E of Ethambutol
Colour blindness and reduced visual acuity
Which TB drugs are associated with hepatotoxicity?
Rifampicin, isoniazid and pyrazinamide
