infectious diseases of the skin and eyes
TRANSCRIPT
Infectious Diseases of the Skin and Eyes
Skin Structure
Natural Defenses of the Skin
• Keratin
• Skin sloughing
• Sebum: low pH, high lipid
• Sweat: low pH, high salt
–Lysozyme digests peptidoglycan
Normal Skin Flora
• Propionibacterium acnes
• Staphylococci
–Staphylococcus epidermidis
– [Staphylococcus aureus]
• Streptococci
• Candida albicans (yeast)
The Eye
• Normal flora sparse
• Similar to skin flora
• Tears have lysozyme
Acne
• Propionibacterium acnes: Gram + rod
• Digests sebum
• Attracts neutrophils
• Neutrophil digestive enzymes cause lesions
Acne
• Most common skin disease in humans
• Oil-based cosmetics worsen disease
• No effects of diet
Acne Treatments
• Benzoyl peroxide dries plugged follicles
• Erythromycin (antibiotic)
• Accutane – inhibits sebum formation
Necrotizing Fasciitis
• Streptococcus pyogenes (Group A Strep = GAS)
• Gram + cocci
• Rapidly spreading cellulitis may lead to loss of limb
Streptococcus pyogenes
• Many exotoxin virulence factors
– M protein: adherence
– Hemolysins: lyse blood cells
– Streptokinase: digests clots
– Hyaluronidase: digests connective tissue
Necrotizing fasciitis
• Disease starts as localized infection• Pain in area, flu-like symptoms• Invasive and spreading• May lead to toxic shock (drop in blood
pressure)• Incidence 1-20/100,000• 30-70% mortality• Surgical removal, antibiotics
Hansen’s Disease: Leprosy
• Disease of skin and nerves
• Change of pigmentation, loss of sensation
• Difficult to transmit• Droplet or skin
contact?• Slow progressing
Hansen’s Disease: Leprosy
• Mycobacterium leprae
• Acid fast bacterium
• Strict parasite
• Multiplies within macrophages
• Prefers cooler areas of body
• Slow growth
Hansen’s Disease: Leprosy• Requires Th1 cells to
activate macrophages to kill M. leprae = cellular immunity
• People with strong humoral response have faster progression
• Long course, drug cocktail