Mycobacteria

Question 1

clinical diseases in the mycobacterium category

Answer 1

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

Question 2

TB epidemiology

Answer 2

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

Question 3

M. tuberculosis complex

Answer 3

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

Question 4

mycobacterium tuberculosis - physiology

Answer 4

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

Question 5

mycobacterium tuberculosis - waxy cell envelope

Answer 5

*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

Question 6

mycobacterium tuberculosis - virulence factors

Answer 6

*cord factor (TDM)
*sulfatides

Question 7

mycobacterium tuberculosis - cord factor

Answer 7

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

Question 8

mycobacterium tuberculosis - sulfatides

Answer 8

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

Question 9

mycobacterium tuberculosis - acid-fast stain

Answer 9

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

Question 10

mycobacterium tuberculosis - acid-fast culture

Answer 10

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

Question 11

mycobacterium tuberculosis - pathogenesis, ID50, and formation of ?

Answer 11

*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

Question 12

mycobacterium tuberculosis - caseating granulomas

Answer 12

*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

Question 13

mycobacterium tuberculosis - risk factors

Answer 13

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

Question 14

mycobacterium tuberculosis - Ghon complex

Answer 14

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

Question 15

mycobacterium tuberculosis - latent TB

Answer 15

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

Question 16

mycobacterium tuberculosis - active TB

Answer 16

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

Question 17

mycobacterium tuberculosis - s/s of active TB

Answer 17

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

Question 18

mycobacterium tuberculosis - risk factors of progression to active TB

Answer 18

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

Question 19

mycobacterium tuberculosis - screening for latent TB

Answer 19

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

Question 20

mycobacterium tuberculosis - screening for active TB

Answer 20

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

Question 21

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

Answer 21

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

Question 22

cavitary tuberculosis

Answer 22

*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 +

Question 23

miliary tuberculosis

Answer 23

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

Question 24

common sites of extrapulmonary TB

Answer 24

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

Question 25

TB - management principles

Answer 25

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

Question 26

leprosy (Hansen’s disease)

Answer 26

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

Question 27

leprosy - clinical disease

Answer 27

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

Question 28

non-tuberculous mycobacterium (NTM)

Answer 28

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

Question 29

non-tuberculous mycobacterium (NTM) - MAC/MAI

Answer 29

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

Question 30

non-tuberculous mycobacterium (NTM) - M. scrofulacem

Answer 30

*causes cervical lymphadenitis
*more common in children

Question 31

non-tuberculous mycobacterium (NTM) - M. marinum

Answer 31

*causes nodular skin lesion
*associated with water