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Lecture 71: (Micro)- Bacteria 3, Respiratory Pathogens, Summary of Upper…

- - - - Capsule
        
        responsible for virulence!
        
        made of polysaccharide!
        
        inhibits phagocytosis except in presence of specific antibodies
        
        antibodies directed against capsular polysacc.
      - Pneumolysin
        
        hemolysin related to streptolysin O (possibly damaged ciliated epithelial cells)
      - IgA protease
        
        disrupts secretory IgA-mediated clearance of organisms
      - Teichoic Acid
        
        activates alternative complement pathway
      - Phosphorylcholine
        
        binds PDE-activating factor, allowing bacteria to enter host cells
  - - - Etiological agent- *Strept. pneumoniae
      - causes "lobar" pneumonia
      - common in healthy young-middle age adults, esp. men
        
        Rare in infants & elderly, but LETHAL!
      - Sudden onset, fever, chills (clasic- single, shaking chill), "rusty" thick sputum
      - Common finding: Pleural involvement w/chest pain
      - Pathogenesis:
        
        Aeoroslized bacteria inhaled into alveoli OR already colonized bacteria -> lungs
        
        inflammatory response ensues w/filling of alveoli w/edema fluid
        
        congestion -> massive outpouring of PMN
        
        macrophages appear that phagocytize PMNs!
        
        Intra-alveolar hemorrhage (red hepatization)
      - Diagnosis
        alpha-hemolysis!
        optochin-disk sensitivity
    - - 1st or 2nd most common cause of bacterial meningitis (adults)
      - may arise as complication of pneumonia, sinusitis or skull fracture
    - - single most common cause of acute ear infections (kids/adults)
    - - major cause & it may occur at all ages
    - - commonly occurs w/development of pneumonia, meningitis
- - - - Virulence!
        polysacc.
        inhibits phagocytosis
  - - - most common cause of pediatric meningitis!
      - 50% incidence of permanent sequelae such as hearing loss, delayed language dev., mental retardation & seizures :!:
      - prompt antibiotic intervention lowers mortality but does NOT reduce incidence of sequelae :!:
  - - - Less serious (otitis, cellulitis)
        
        ampicilllin or sulfisoxazole orally
  - - - Hib (type b) vaccine first given at 2 months of age! :!!:
- - - - Myoplasma most common cause of pneumonia in kids ages 5-15 :!!:
- - - - fragile gram-negative coccobacilli
  - - - 1) Catarrhal
        
        like COMMON COLD
        
        VERY contagious during this stage before diagnosis!
      - 2) Paroxysmal
        
        begins 10-14 days into illness; char. by 5-15 rapidly consecutive coughs followed by "whoop"
      - 3) Convalescent
        
        at 28 days
    - - pneumothorax
        convulsions
        cerebral hemorrhage/edema
        encephalitis
        etc, etc.
  - - - but antibiotics can prevent complications
- - - - colonies often highly mucoid
  - - - interacts with macrophages to stimulate release of interleukin-1
        --> increases body temp. via hypothalamus!
    - - resists phagocytosis
        very mucoid/viscous!