Infectious Diseases - Travel Related Infection Flashcards
What is the causative organism of tuberculosis (TB)?
Mycobacterium tuberculosis
What are the risk factors for TB?
- known contact with active TB
- immigrants from areas of high TB prevalence
- people with relatives or close contacts from countries with a high TB prevalence
- immunosuppression
- IVDU
Outline the disease course of TB.
TB is spread by inhaling saliva droplets from infected people, spreading through the lymphatics and blood to form granulomas around the body.
Active TB is when there is active infection within the body. In most cases the body can mount a significant immune response and clear the infection.
Latent TB occurs when the immune system encapsulates sites of infection, but does not clear the infection.
Secondary TB occurs when latent TB reactivates.
When the immune system cannot control the disease, TB becomes disseminated. This is miliary TB.
What is the most common site for TB granuloma formation?
The lungs - TB have a high oxygen demand, so thrive in the oxygen-rich environment of the lungs.
Give some extrapulmonary TB manifestations.
- lymph nodes
- pleura
- central nervous system
- pericardium (e.g. pericardial effusion / tamponade)
- gastrointestinal system
- genitourinary system
- bones and joints
- cutaneous TB
Presentation of TB.
- lethargy
- fever / night sweats
- weight loss
- cough (?haemoptysis)
- lymphadenopathy
- erythema nodosum
- spinal pain in spinal TB (ie. Pott’s disease)
What is the Mantoux test?
Mantoux test - tuberculin injected into the intradermal space, creating a bleb under the skin. NICE suggest considering an induration of 5mm or more a positive result, suggesting previous vaccination, latent or active TB.
After a positive result, patients should be assessed for active disease.
What is the Interferon-Gamma Release Assay (IGRA) test?
Blood sample is mixed with antigenic material from the TB bacteria. If interferon-gamma is released from the white blood cells, this is considered a positive result and indicates active TB.
What are the x-ray findings of primary TB?
- patchy consolidation
- pleural effusion
- hilar lymphadenopathy
What are the x-ray findings of secondary TB?
- patchy or nodular consolidation
- cavitation
- affecting upper zones
What are the x-ray findings of miliary TB?
Millet seeds uniformly distributed throughout the lung fields.
What are the ways to collect cultures for tuberculosis?
- sputum culture (3x)
- Mycobacterium blood cultures (require a special culture bottle)
- lymph node aspiration or biopsy
Management of acute pulmonary TB.
R - Rifampicin for 6/12
I - Isoniazid for 6/12
P - Pyrazinamide for 2/12
E - Ethambutol for 2/12
A patient with tuberculosis is started on rifampicin, isoniazid, pyrazinamide and ethambutol. What should also be prescribed?
Pyroxidine - co-prescribed prophylactically to reduce the risk of peripheral neuropathy from isoniazid.
What are the side effects of Rifampicin?
- red / orange discolouration of urine
- inducer of CY P450 so reduced drugs metabolised by this system (e.g. COCP)
- hepatotoxic
rifampicin (“red-an-orange-pissin’”)
How does HIV cause immunosuppression?
HIV enters and destroys CD4+ T helper cells.
