Mycobacteria Flashcards
Mycobacterium tuberculosis
lab tests
Shoot out at the TB Corral
- Acid fast (carbol fuschien stain; mycolic acids)
- Lowenstein medium
- Obligate Aerobe
- Test for TB with PPD, BCG vaccine will always show (+) skin test.
- Proliferates in macrophages
- Clumping of bacteria into serpentine formation (cord factor)
Mycobacterium tuberculosis
VF
Shoot out at the TB Corral
- Cord factor (Glycolipid responsible for clumping of bacteria into serpentine formation).
- Sulfatides (prevent phagolysosome fusion).
Mycobacterium tuberculosis
MOA
Shoot out at the TB Corral
- Human to human respiratory spread.
- Cord factor ⬆ granuloma formation by ⬆ TNF-a.
(Allows TB to attract and hide in macrophage granulomas)
- Sulfatides prevent phagolysosome fusion
(Allows TB to survive in macrophages by creating incompetent secondary lysosomes preventing fusion with phagosomes to prevent phagolysosome formation, thus avoiding exposure to the lysosomal hydrolases)
Mycobacterium tuberculosis
Paths of progression of TB after primary infection
Shoot out at the TB Corral
- Healed latent infection
- Systemic infection (Miliary TB)
- Reactivation TB
Mycobacterium tuberculosis
Healed latent infection
Shoot out at the TB Corral
- Primarily lower or middle lobes of lungs.
- Usually in children
- Long fever
- usually resolves by fibrosis and becomes latent
- GHON complex
- TB resides in broken down necrotic macrophages (Langerhans giant cells) → Caseation Granulomas
Mycobacterium tuberculosis
GHON complex
Shoot out at the TB Corral
Visual calcification of lung parenchyma and hilar lymph nodes.
(Hilar lympadenopathy + peripheral granulomatous lesion in middle or lower lung lobe).
Lesion heals → eventually becomes fibrotic and calcifies, along with nearby draining (hilar) lymph nodes.
Mycobacterium tuberculosis
(+) TB PPD skin test
Shoot out at the TB Corral
Type 4 hyper sensitivity reaction
PPD will show positive for:
- active infections
- latent infections
- prior BCG vaccine (attenuated)
Mycobacterium tuberculosis
Systemic infection (Miliary TB)
Shoot out at the TB Corral
- Multi-organ failure
- Primarily bone, liver, and lymphatics, but can spread to any organ in the body
- Can be lethal
Mycobacterium tuberculosis
Reactivation TB
(occurs in only 5-10% of TB pt)
Shoot out at the TB Corral
- Usually in upper lobes
- Associated with immunosuppression (HIV, old age, cancer) through the ⬇ regulation of TNF-a release
- Always screen for PPD before using TNF inhibitors!!!
- Cough, night sweats, hemoptysis (bloody cough)
- Cachexia (body wasting)
- Skeletal system: Pots disease
- CNS involvement: meningitis or tuberculoma (cavitary lesion) in 10-15% of reactivations
Mycobacterium tuberculosis
Pots disease
Shoot out at the TB Corral
When TB infects the spinal column.
Usually multiple vertebrae.
Demineralization of the bone, spinal weakness, soft tissue swelling (swelling leads to pain).
Can lead to abcess formations, spinal deformities, and weakness due to loss of support.
Mycobacterium tuberculosis
treatment
Shoot out at the TB Corral
mnemonic RIPE
- Rifampin
- Isoniazid
- Pyrazinamide
- Ethambutol
For prophylaxis: Rifampin and Isoniazid for 9 months
Mycobacterium leprae (Hanson’s disease)
lab tests
The good, the bad, and the lion faced
Acid fast (carbol fuschien stain; mycolic acids).
Thrives in cool temperatures → growth in extremities.
Mycobacterium leprae (Hanson’s disease)
source
The good, the bad, and the lion faced
Armadillos are the major reservoir
Mycobacterium leprae (Hanson’s disease)
presentation #1
(Tuberculoid presentation)
The good, the bad, and the lion faced
- Helper TH1** cells stimulate macrophages to engulf the bacteria (in cell mediated immunity).
- Mild symptoms, well demarcated hairless lesions on skin.
- Lepermans skin test (tests for immune rx similar to TB test)
Mycobacterium leprae (Hanson’s disease)
presentation #2
(Lepromatous presentation)
The good, the bad, and the lion faced
- TH2** cells promote humoral (antibodies etc) response
- very weak or non existant TH1 response, bacteria unable to be contained by macrophages.
- High chance of transmission human to human
- Distal portions are affected in a glove and stocking pattern.
- Poorly demarcated lesions on extensor surfaces (extensor surfaces are cooler!)
- Leonine faces, facial deformity. (thickening of skin, loss of eyebrows and eyelashes, collapse of nose, nodular earlobes)
Mycobacterium leprae (Hanson’s disease)
treatment
The good, the bad, and the lion faced
- For TH1 Tuberculoid form:
Dapsone and rifampin for 6 months
- For TH2 Lepromatous form:
Dapsone, rifampin, and clofazimine for 2-5 years
