Mycobacteria Flashcards

1
Q

clinical diseases in the mycobacterium category

A
  1. tuberculosis
  2. leprosy
  3. non-tuberculous mycobacterial (NTM) infections
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2
Q

TB epidemiology

A

*about 25% of the world’s population has infection (most is latent)
*TB is one of the deadliest diseases in the world

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3
Q

M. tuberculosis complex

A

M. tuberculosis, M. africanum, M. bovis, M. miroti

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4
Q

mycobacterium tuberculosis - physiology

A

*acid-fast bacilli
*aerobic
*non-spore forming
*WAXY CELL ENVELOPE

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5
Q

mycobacterium tuberculosis - waxy cell envelope

A

*made of mycolic acids & lipids
*confers acid-fastness and impermeability to gram staining
*resistance to acid, alkali, drying, and germicides
*KILLED BY HEAT
*resistance to killing by antibody and complement
*slow growth

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6
Q

mycobacterium tuberculosis - virulence factors

A

*cord factor (TDM)
*sulfatides

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7
Q

mycobacterium tuberculosis - cord factor

A

-most abundant glycolipid in the mycobacterial CELL WALL
*toxic to mammalian cells
*inhibits neutrophils (PMNs)
*causes organism to cluster/arrange into “serpentine cords”

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8
Q

mycobacterium tuberculosis - sulfatides

A

*surface glycolipids
*INHIBIT fusion of phagosome and lysosome
*avoid exposure to lysosomal hydrolases (avoid host defenses)

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9
Q

mycobacterium tuberculosis - acid-fast stain

A

*use acid-fast stain for TB
*stain a RED color
*termed “red snappers”

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10
Q

mycobacterium tuberculosis - acid-fast culture

A

*culture is the gold standard for TB
*both solid and liquid media used
*slow growing (must incubate for a while)

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11
Q

mycobacterium tuberculosis - pathogenesis, ID50, and formation of ?

A

*acquired by INHALATION of aerosolized respiratory droplets
*LOW INFECTIOUS DOSE (ID50)
*pulmonary macrophages phagocytose the TB, but do not kill, so they proliferate
*T cells initiated
*macrophages and T cells wall of the infection, forming GRANULOMAS

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12
Q

mycobacterium tuberculosis - caseating granulomas

A

*caseation (middle of granuloma) = areas of necrosis, loss of tissue architecture
-caused by TNF, ROS, and cytotoxic agents
*granuloma = rim of healthy macrophages and T cells that are walling off; keeps TB from spreading throughout the body

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13
Q

mycobacterium tuberculosis - risk factors

A

*exposure / environmental factors
impaired immunity (esp HIV**)

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14
Q

mycobacterium tuberculosis - Ghon complex

A
  1. ghon focus/lesion - initial granuloma formed
  2. hilar lymphadenopathy
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15
Q

mycobacterium tuberculosis - latent TB

A

*immune system contains infection
*asymptomatic
*NOT contagious
*CAN advance to active TB

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16
Q

mycobacterium tuberculosis - active TB

A

*TB is active and grows in the body
*patients develop symptoms
*can spread from person to person (contagious)
*progressive disease can result in death

17
Q

mycobacterium tuberculosis - s/s of active TB

A

*fever
*night sweats
*weight loss
*cough
*hemoptysis (coughing up blood)

18
Q

mycobacterium tuberculosis - risk factors of progression to active TB

A

***HIV infection
**malnutrition
-intensity of exposure
-age
-alcohol use disorder
-diabetes
-homelessness/incarceration
-immunosuppression

19
Q

mycobacterium tuberculosis - screening for latent TB

A
  1. tuberculin skin test
    OR
  2. interferon gamma release assay (IGRA)
20
Q

mycobacterium tuberculosis - screening for active TB

A
  1. imaging (CXR or CT)
  2. sputum (AFB smear & culture; PCR)
  3. biopsy
21
Q

mycobacterium tuberculosis - suspected active TB management (waiting for Dx)

A

*should be placed in special respiratory isolation (negative pressure room + N95 masks)

22
Q

cavitary tuberculosis

A

*classic REACTIVATION disease (from latent to active)
*s/s: fever, night sweats, weight loss, productive cough
*CXR with cavities (esp apical)
*high communicability
*dx: AFB smears and cultures +

23
Q

miliary tuberculosis

A

*disseminated form of T, spread through the BLOOD
*lung involvement + EXTRAPULMONARY sites
*characteristic “millet seeds” on CXR

24
Q

common sites of extrapulmonary TB

A

-meningitis
-pleuritis
-pericarditis
-renal TB
-spine
-lymphadenitis (scrofula)

25
Q

TB - management principles

A

*long-term Rx with a COMBINATION of drugs (for ACTIVE TB)
*2 phases (initial intensive + continuation phase)

26
Q

leprosy (Hansen’s disease)

A

*acid-fast bacillus (M. leprae)
*primarily infects SKIN and PERIPHERAL NERVES (esp hands/feet)

27
Q

leprosy - clinical disease

A
  1. lepromatous (multibacillary) - diffuse presentation, leonine facies; more severe
  2. tuberculoid (paucibacillary) - few hypoesthetic (NO SENSATION) skin plaques
28
Q

non-tuberculous mycobacterium (NTM)

A

*acid-fast bacilli (M. marinum, M. avium complex, or M. scrofulacem)
*found in the ENVIRONMENT

29
Q

non-tuberculous mycobacterium (NTM) - MAC/MAI

A

*can cause:
1. respiratory disease
2. disseminated disease

30
Q

non-tuberculous mycobacterium (NTM) - M. scrofulacem

A

*causes cervical lymphadenitis
*more common in children

31
Q

non-tuberculous mycobacterium (NTM) - M. marinum

A

*causes nodular skin lesion
*associated with water