2: Mycobacterial Infection Flashcards
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
If induration is less than 6mm what should you do
Give TB vaccine
If induration is 6-15mm what does it mean
Hypersensitive to TB
- Previous infection or vaccine
If 6-15mm on TST should individual have vaccine
No
What does induration of more than 15mm mean
Strongly positive to TB - likely current infection
What can cause false negatives of TST
- Miliary TB
- Sarcoidosis
- HIV
- Lymphoma
- < 6 months
What interferon gamma release assay (IGRAS)
Interferon gamma release from T-cells
what investigations are used to identify TB
- CXR
- Sputum smear
- Sputum culture
what will be seen on CXR
- Upper lobe opacities
- Miliary disease
how is a sputum smear taken
3 deep coughs - one early morning sample
what is alternative to sputum smear in children for TB
gastric acid lavages - 3 samples
what is used to test for TB
ziehl-neelsen stain
how will TB present on ziehl-neelsen stain
red (due to being acid-fast)
what is the gold-standard investigation for TB
sputum culture
how long does sputum culture take in liquid media
1-3W
how long does sputum culture taken in solid media
4-8W
what media is used for sputum culture
Lowenstein Jensen
how will TB present in lowenstein-jensen media
Ruff, Buff and tough
what is the role of nucleic acid amplification testing
identify DNA or RNA
what is the diagnosis time for RAAT
8-hours
what may be performed for CNS TB
LP
what will be seen in LP for CNS TB
- Leucocytosis
- Low glucose
- High protein
explain notification for TB
TB is a notifiable disease and CDC should be contact in in 3-days
explain contact tracing for TB
All individuals who do not have TB are sent an anonymous letter inviting them to screening
how is TB managed
RIPE - for 2 months
RI - for 4 moths
what is directly observed therapy
indicated for people with poor concordance - individuals attending 3 times PW where they are rewarded for taking treatment
what are 3 side effects of rifampicin
- Hepatitis
- Orange-secretions
- Flu-like symptoms
explain relationship between rifampicin and CYP450
Rifampicin induces CYP450
what are 3 side effects of isoniazid
- Hepatitis
- Agranulocytosis
- Peripheral neuropathy
how are the side effects of isoniazid controlled for
Give vitamin B6 (pyroxidine) to prevent peripheral neuropathy
what is pyroxidine
vitamin B6
explain relationship between isoniazid and CYP450
isoniazid inhibits CYP450
what are 4 side effects of pyrazinamide
- Hyperuricaemia = precipitate gout
- Arthralgia
- Myalgia
- Hepatitis
what is the side effect of ethambutol
Optic neuritis
what should be checked prior to giving ethambutol
Visual acuity
what drug causes orange secretions
Rifampicin
what drug causes optic neuropathy
Ethambutol
what drug can precipitate gout
Pyrazinamide
what is multi-drug resistant TB
TB resistant to rifampicin and isoniazid
what vaccination is given for TB
BCG
