Questions and Answers
What is the function of the Fc receptor protein in structural defenses?
What is the effect of Leukocydin on leukocytes?
What is the function of Exfoliative toxins?
What type of diseases can Staphylococcus aureus cause?
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What is the mechanism of action of cytolytic toxins?
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What is the purpose of the Pseudopod in structural defenses?
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What is the effect of Epidermal Cell Differentiation Inhibitors?
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What is the purpose of Prevention of Opsonization?
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What is the role of IgG antibody stem regions in structural defenses?
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What is the source of the information about Staphylococcus aureus?
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Study Notes
Otitis Media (OM)
- 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
Otitis Media with Effusion (OME)
- Epidemiology:
- Incidence and prevalence difficult to establish
Chronic Suppurative Otitis Media (CSOM)
- Epidemiology:
- Incidence and prevalence difficult to establish
Causal Pathways for Otitis Media
- Eustachian tube anatomy
- Common otopathogens:
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Pseudomonas aeruginosa
Haemophilus influenzae
- X factor (Hemin) and V factor (NAD+) required for growth
- Virulence factors:
- Adhesins
- Polysaccharide capsule
- Lipid A chains/lipooligosaccharides
- Fimbriae
- IgA protease
- Biofilms
Moraxella catarrhalis
- 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
Streptococcus pneumoniae
- Virulence factors:
- Polysaccharide capsule
- Fimbriae
- Surface proteins that inhibit activation of complement
Pseudomonas aeruginosa
- 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)
Staphylococcus aureus
- 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)
- Enzymes:
Other Diseases Caused by Staphylococcus aureus
- Skin diseases
- Reproductive system diseases
- Systemic infections/cardiovascular diseases
- Respiratory system diseases
- Gastrointestinal system diseases
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Description
This quiz covers the pathogenesis, epidemiology, and treatment of otitis media and externa, including acute otitis media, complications, and otitis media with effusion.
