Tuberculosis Flashcards
what stain is used to detect mycobacterium tuberculosis
acid-fast
shape
- rods (bacilli)
- gram-positive cell wall structrue but stain very weakly with gram stain
complex cell wall rich in lipids called
mycolic acids
the acid-fast cell wall has a resistance to
detergents, many antibiotics, and drying conditions
acid fast cell wall functions
protection from lysis after phagocytosis
* blocks fusion of phagosome with lysosome
* masks PAMPS on the bacterial surface
* capacity for intracellular growth within macrophages –> “facultative intracellular pathogen”
reservoir
human
transmission
respiratory droplet nuclei
high or low infectious dose
low
high or low infectious dose
low
populations at greatest risk for TB
- HIV+
- diabetics
- substance abusers
- low body weight/malnourishment
- immunocompromised
pathogenesis (steps 1-3)
- acid fast bacilli are inhaled and spread to alveoli
- phagocytized by alveolar marcophages
- M. tuberculosis capsule and waxy mycoliv acids block pahgosome form fusing with lysosome to avoid destruction within macrophages
pathogenesis (steps 4-6)
- Mycobacteria mulitply in macrophages (intracellular pathogen). Inflammatory response –> other phagocytes are attracted to the site
- macrophages fuse together to form giant multinelceated cells
- A granuloma (aka a tubercle) forms
active secondary TB disease (step 7 of pathogenesis)
suppressed cell mediated immunity –> macrophages in tubercle die –> mycobacteria, enzymes, cytokines released –> forming area of necrosis
* tubercle ruptures, releases live mycobacteria into airways
* causes large defect called tuberculous cavity
* can be transmitted by coughing
active TB signs and symptoms
- chronic cough
- bloody rust-colored sputum
- high fever
- night sweats
- weight loss
- fatigue
miliary TB
when TB gets into ciruclation and spreads systemiclaly to all parts of the body
