Micro Chapter 21- skin and eye infections

Skin and Eye Infections

Structure of Human Skin

  • Key components include hair follicles, oil glands, sweat glands, blood vessels, and nerve tissues.

Rashes

  • Macular: Flat, reddened lesions.

  • Papular: Raised lesions.

Staphylococcal Skin Infections

  • Gram-positive clusters.

  • Treatment includes penicillin, methicillin, and vancomycin (for MRSA).

  • Staphylococcus epidermidis: Normal skin microflora, pathogenic in broken skin.

  • Staphylococcus aureus: Most pathogenic; produces toxins, causes folliculitis, sty, and boils.

Impetigo

  • Highly contagious, primarily in young children; typically caused by Staphylococcus.

  • Symptoms: rupturing lesions, crusting.

  • Scalded skin syndrome: Toxins cause skin layer separation.

Streptococcal Skin Infections

  • Gram-positive in chains with hemolysin toxins.

  • Streptococcus pyogenes: Group A beta hemolytic; causes necrotizing fasciitis ("flesh-eating" disease) and has a mortality rate of 40%.

  • Treatment includes penicillin and clindamycin.

Smallpox

  • Caused by variola virus; eradicated due to effective vaccination.

Chickenpox & Shingles

  • Caused by varicella-zoster virus, a double-stranded DNA virus.

  • Initial mild childhood disease; remains latent and can reactivate as shingles in later life.

Herpes Simplex Virus (HSV)

  • HSV1: Oral herpes (cold sores); remains latent.

  • HSV2: Genital herpes.

  • Treatment includes acyclovir.

Measles

  • Caused by measles virus; spread via respiratory route.

  • Symptoms: macular rash and Koplik’s spots in mouth.

  • Vaccination: MMR.

Rubella

  • Milder than measles with a rash and low fever; last epidemic in 1965.

  • Vaccination: MMR.

Common Childhood Viral Infections

  • Fifth disease: mild with a "slapped-cheek" rash.

  • Roseola: high fever followed by rash.

  • Hand-foot-and-mouth disease: rash and fever.

Fungal Infections

  • Candida albicans: Yeast infection; treated with antifungals.

  • Tinea: Fungal skin infections (e.g., ringworm, athlete's foot).

Conjunctivitis

  • Inflammation of conjunctiva (pinkeye); commonly caused by Haemophilus influenzae (bacterial) or adenoviruses (viral).

  • Treatment: antibiotic eye drops for bacterial infections.