Biofilm Infections

Question 1

Staphylococcus aureus

Answer 1

Biofilm Infx
• Gr+ cocci, often *clusters
• Facultative anaerobes
• *Beta hemolysis
• *Catalase +
• *Coagulase + 
• *Mannitol + 
• Grow in high salt
LAB
• Mannitol salt agar
Virulence
• *Protein A
• *Fibronectin, Fibrinogen, elastin-binding protein
• *Hyaluronidase

Question 2

Staphylococcus epidermidis

Answer 2

Biofilm Infx
• Gr+ cocci, often *clusters
• Major healthcare-associated opportunist, major cause prosthetic and catheter infect.
• *Gamma hemolysis
• *Catalaste +
• *Coagulase –
• *Mannitol – 
Virulence
• *Adhesins 
• *Collagen, fibronectin, fibrinogen, elastin
• **Slime layer
• **Biofilms
• Lipases, proteases

Question 3

Pseudomonas aeruginosa

Answer 3

Biofilm Infx
• Gr- rod
o *Healthcare associated infections (HAIs)
• Encapsulated
• Motile, flagella
• Aerobe
• Oxidase +
• Nonfermenter
• Wide temp. range, 4-42°C
• Salt-tolerant
LAB
• Growth in distilled H20
 • Growth on variety media, often blood, MacConkey
   o Mucoid colonies
   o +/- odor of grapes 
   o +/- color
      o Pyocyanin (blue)
      o Pyoverdin (green, fluorescent [wounds])
Virulence
• *Pili
• *Capsule (mucoid polysaccharide alginate
• *Exotoxin A 
 • *Biofilm formation
o *Alginate major component
• *Intrinsic and acquired antibiotic resistance 
• Collagenase
• Elastase
• Phospholipase (β-hemolysis)
• Protease
• Siderophores

Question 4

Candida albicans

Answer 4

Biofilm Infx
• *Dimorphic fungus
• Opportunist
• Risk factors
    o Antibiotics, ↓CMI, diabetes, elderly, catheter
• Dimorphic (poly!) yeast 
    o Round to oval budding yeasts, pseudohyphae
    o True hyphae
LAB
• *Germ tube test for C. albicans… DIAGNOSTIC
• Direct microscopic examination most Rapid and cost effective
• Sabouraud dextrose agar (SDA)
Virulence
- adhesins
- proteinases 
- phospholipases
- biofilms
- dimorphic