Mycobacteria Flashcards
clinical diseases in the mycobacterium category
- tuberculosis
- leprosy
- non-tuberculous mycobacterial (NTM) infections
TB epidemiology
*about 25% of the world’s population has infection (most is latent)
*TB is one of the deadliest diseases in the world
M. tuberculosis complex
M. tuberculosis, M. africanum, M. bovis, M. miroti
mycobacterium tuberculosis - physiology
*acid-fast bacilli
*aerobic
*non-spore forming
*WAXY CELL ENVELOPE
mycobacterium tuberculosis - waxy cell envelope
*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
mycobacterium tuberculosis - virulence factors
*cord factor (TDM)
*sulfatides
mycobacterium tuberculosis - cord factor
-most abundant glycolipid in the mycobacterial CELL WALL
*toxic to mammalian cells
*inhibits neutrophils (PMNs)
*causes organism to cluster/arrange into “serpentine cords”
mycobacterium tuberculosis - sulfatides
*surface glycolipids
*INHIBIT fusion of phagosome and lysosome
*avoid exposure to lysosomal hydrolases (avoid host defenses)
mycobacterium tuberculosis - acid-fast stain
*use acid-fast stain for TB
*stain a RED color
*termed “red snappers”
mycobacterium tuberculosis - acid-fast culture
*culture is the gold standard for TB
*both solid and liquid media used
*slow growing (must incubate for a while)
mycobacterium tuberculosis - pathogenesis, ID50, and formation of ?
*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
mycobacterium tuberculosis - caseating granulomas
*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
mycobacterium tuberculosis - risk factors
*exposure / environmental factors
impaired immunity (esp HIV**)
mycobacterium tuberculosis - Ghon complex
- ghon focus/lesion - initial granuloma formed
- hilar lymphadenopathy
mycobacterium tuberculosis - latent TB
*immune system contains infection
*asymptomatic
*NOT contagious
*CAN advance to active TB