1. Staphylococcus aureus
2. Streptococcus pyogenes
3. Streptococcus pneumoniae
4. Enterococcus sp.

• GM+
• Staphylococcus
• Adaptable
  • Wide temp range - high temps
  • Facultative anaerobe
  • pH extremes
  • Metabolically versatile
  • Viable after air drying
  • Resistant to antibiotics - MRSA/VRSA

1. Enzymes
2. Exotoxins
3. Cell Bound

• Coagulase - coagulates plasma and blood, antiphagocytic
• Hyaluronidase - digests hyaluronic acid (cell cement), spreading factor
• Staphylokinase - digests blood clots
• DNase - destorys chemical structure of DNA
• Lipase - digest lipids on skin, helps skin colonization
• Penicillinase (Beta-lactamase) - penicillin resistant.

1. Hemolsoins - lyse RBCs
2. Leukocidin - lyse PMNs and M0, antiphagocytic
3. Enterotoxins - in GI, food poisoning
4. Exfoliative toxin - seperates epidermis from dermis i.e. SSSS
5. Toxic Shock Syndrome Toxin (TSST)

• Protein A - stuck to surface of MO
• Binds to FC region of IgG
• Antiphagocytic

• Most humans
• Fomites

• Humans reservoirs 20-60%
• Carried in RT, GI
• Asymptomatic

How is S. aureus transmitted?

• Respiratory droplets
• Fomites
• Contaminated foods

• Poor hygiene / nutrition
• Tissue injury
• Immunodeficiecy
• Staph of newborn
• Surgical wards
• 3rd most common nosocomial

1. Localized skin infections
2. Systemic infectons
3. Toxigenic diseases

1. Folliculitus - infection of hair folicules
2. Furuncle (boil) - abscess of skin
   • lipase destroys skin, coagulase walls of IR
3. Carbuncle (spreading boil)
   • staphylokinase - digest blood clots
   • hyaluronidase destroy cell cement and spreads
4. Impetigo - resembles a localized SSSS

1. Osteomyelitis - bone end (spongy, blood cells) infections
2. Pnneumonia - not most common cause
3. Bacteremia (infection in blood)
   • Abcess in organ
   • Endocarditis - lining of heart
   • Meningitidis - lining of brain and spinal cord
   • Joint infections
   • Cellulitis

1. Food Intoxication (poisoning)
   • Ingested enterotoxin
   • Cramping, diarrhea
   • Symptoms in 2-6hrs, recover 24hrs
   • Prevention - refrigeration, handwashing
2. Staphylococcal Scalded Skin Syndrome (SSSS)
   • Exfoliative toxin causes toxemia
   • Umbilical stump and eyes
   • Red rash, blisters, epidermis seperates from dermis
3. Toxic Shock Syndrome
   • TSST in blood
   • Caused by high absorbant tampons (magnesium)
   • Fever, vomiting, rash, damage to kidneys, liver

1. Phagocytosis and opsonization by C
2. Inflammation
3. Antibodies
4. Foreign body response - stiches and metal allow MO to adhere

• Abscess - open lesion, remove pus
• Systemic - long term IV or oral therapy

What is the prevention for S. aureus infections?

• Handwashing, refrigeration
• Nosocomial
  • Sterilization of instruments, catheters, needles
  • Isolation of open lesions
  • Proper disposal of dressings