BMS Wk 5 lec 3

Study Notes

Acute Otitis Media (AOM) complications:
- Acute mastoiditis
- Meningitis
- Brain abscesses
21,000 deaths from AOM per year
30 per 10,000 individuals: hearing loss
Perforation of tympanic membrane

Eustachian tube anatomy
Common otopathogens:
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Pseudomonas aeruginosa

Gram-negative, diplococcus, aerobic bacteria
Common in URT, middle ear, eye infections
Commonly resistant to beta lactam drugs
Part of normal microbiota of ~3% of people (children more)
Variable rates of colonization in communities
Virulence factors:
- Antibiotic resistance (b-lactamase resistance)
- Outer membrane proteins (uspA1-A2, Pili)
- Iron-regulated proteins (transferrin-binding proteins, lactoferrin-binding proteins)
- Lipid A chains/lipooligosaccharides

Virulence factors:
- Polysaccharide capsule
- Fimbriae
- Surface proteins that inhibit activation of complement

Causes otitis externa
Virulence factors:
- Fimbriae and adhesins for attachment
- Formation of biofilms
- Produces enzymes like elastase, which breaks down elastic fibers and degrades complement system
- Pyocyanin triggers free radical accumulation, causing tissue damage
Epidemiology:
- Found mostly in soil, not a component of regular microbiota
- Common nosocomial infection agent (10% of hospital infections)

Salt-tolerant, facultative anaerobe, resistant to desiccation, UV radiation, and heat
Along with Staphylococcus epidermidis, makes up ~90% of skin microbiota
Common cause of otitis externa
Virulence factors:
- Enzymes:
  - Coagulase, Hyaluronidase, Staphylokinase
  - Lipase, beta-lactamase
- Structural defenses:
  - Capsule/slime layer glycocalyx
  - Binding IgG antibody stem regions
- Toxins:
  - Cytolytic toxins to disrupt membranes
  - Leukocydin to kill leukocytes
  - Epidermal cell differentiation inhibitors
  - Exfoliative toxins (Toxic Shock Syndrome Toxin)