2: Mycobacterial Infection Flashcards
(63 cards)
What is mycobacterium TB
Infection with mycobacterium TB
What countries have the highest incidence of TB
Phillipines
Indonesia
China
What type of organism is mycobacterium TB
Aerobic gram-positive, acid-fast bacilli
What is mycobacterium bovis
Mycobacterium bovis causes GI TB leading to increase incidence of colorectal cancer
What are 4 RF for mycobacterium TB
- Immunosuppressed
- High-risk setting
- Malnutrition
- Lung disease
Name 3 immunosuppressed patients
HIV
Diabetics
Corticosteroids
Alcoholics
What is the biggest killer in HIV patients
TB
How do patients present in latent infection
Asymptomatic
Are patients contagious in latent infection
No
What are the two types of active infection
Primary and re-activation
Are individuals contagious in active infection
Yes
How does active infection of TB present
- Constitutional: weight-loss, night sweats, malaise, fever
- Pulmonary: haemoptysis and dyspneoa
What % of individuals with TB have extra-pulmonary features
20
What are the symptoms of TB lymphadenitis
Painless enlargement of sub-clavicular and axillary lymph nodes
How does GI TB present
Vomiting, colicky abdominal pain as inflammation can cause adhesions and bowel obstruction
What is spinal TB called
Pott’s disease
What is miliary TB
Haematogenous spread of TB throughout the lung
How does CNS TB present
Rupture of foci can cause meningitis
What is a feature of GU TB
Sterile pyuria
How does cutaneous TB present
Painful red nodules usually on the face
Explain pathophysiology of TB infection
- TB enters lungs
- Macrophages engulf TB into a phagosome
- Lysosome then fuses with phagosome. This environment enables TB to survive
- TB proliferates to cause a localised infection
- Cell-immunity is then activated and surrounds TB to form a granuloma
- TB in the centre then dies - presenting as caseous necrosis
- TB also enters Hilary lymph node carried by lymph and other immune cells. Ghon focus and lymph node involvement is termed the Ghon complex
- The tissue in the ghon complex calcifies to form a ranke complex
- If a person is immunocomprimsied it becomes reactivated and moves to the upper part of the lung
- When re-actvate immune system memory T cells try to fight infection causing damage resulting in cavitation causing infection to disseminate
- If haematogenously it causes miliary TB
What type of hypersensitivity reaction is TB
Type IV hypersensitivity reaction
What is the Mantoux test
Intradermal infection of purified protein derivative tuberculin
What does a induration of less than 6mm mean
Negative
