Bacterial and Viral Diseases of the Skin

Structure of the Skin

• The skin has multiple layers and structures that play vital roles in protection and sensation.
  • Epidermis:
  • Comprises several strata including:
    • Stratum Corneum: Outermost layer consisting of dead cells.
    • Stratum Granulosum: Involves keratin production.
    • Stratum Spinosum: Provides strength and flexibility.
    • Stratum Basale: Innermost layer where cell division occurs.
  • Dermis:
  • Contains blood vessels, nerve endings, hair follicles, and glands (sweat and sebaceous).
  • Supports the epidermis and provides strength and elasticity.
  • Hypodermis (Subcutis):
  • Composed of fat and connective tissue, providing insulation and cushioning.
• Microbiota: Skin is home to diverse microorganisms that contribute to skin health.

Wounds and Infection

• Wounds: Damage to skin and underlying tissue from trauma (e.g., cuts, burns, bites).
  • Can allow microbes to penetrate deeper tissue leading to potential infections.
  • Body's defenses usually combat infections, but severe cases can arise.

Bacterial Diseases of the Skin and Wounds

• Folliculitis:

  • Infection of hair follicles; manifests as pimples or sties.
  • Can develop into furuncles (boils) or carbuncles (multiple boils).
  • Most commonly caused by the bacterium Staphylococcus aureus.
  • Diagnosis: Detection of Gram-positive bacteria in pus.
  • Treatment: Dicloxacillin for staphylococcal infections; topical treatments include Mupirocin.

• Staphylococcal Scalded Skin Syndrome (SSSS):

  • Caused by exfoliative toxins from some Staphylococcus aureus strains.
  • Unlike other skin infections, the dermis is unaffected, leading to no scarring.
  • Primarily affects infants; spread occurs person-to-person.

• Methicillin Resistant Staphylococcus aureus (MRSA):

  • Can be asymptomatic in carriers yet contagious.
  • Common in healthcare settings. Symptoms include skin lesions and inflammation.
  • Treated with Vancomycin or Nafcillin.

• Streptococcal Infections (Impetigo and Erysipelas):

  • Impetigo: Highly contagious skin infection leading to vesicles; often treated with penicillin derivatives. Primarily affects children.
  • Erysipelas: Characterized by red, swollen areas typically on the face or legs mostly affecting the elderly.
  • Microorganism: Generally caused by Streptococcus pyogenes.

• Necrotizing Fasciitis:

  • Severe infection often caused by S. pyogenes that leads to rapid tissue destruction.
  • Requires prompt treatment with antibiotics; difficult to diagnose early due to nonspecific symptoms.

• Pseudomonas Infection:

  • Caused by Pseudomonas aeruginosa, prevalent in moist environments.
  • Associated with infections in burn patients and can lead to severe complications.

• Acne:

  • Common skin condition caused by Propionibacterium acnes.
  • Managed through antibiotics and topical treatments that promote skin cell exfoliation.

• Cutaneous Anthrax:

  • Caused by Bacillus anthracis, presents as eschars.
  • Found in cattle handlers and treated with Ciprofloxacin.

• Warts:

  • Benign skin growths caused by various types of papillomaviruses.
  • Treatment options include physical removal and the Gardasil vaccine protects against high-risk strains.

Viral Diseases of the Skin and Wounds

• Herpes Infections:

  • Spread through mucous membranes and are typically not life-threatening.
  • Treated with antiviral drugs such as Acyclovir.

• Measles:

  • Caused by Morbillivirus with symptoms like Koplik's spots and a red rash.
  • Preventative measures involve MMR vaccination.

• Rubella:

  • Caused by the rubella virus, with vaccination preventing congenital rubella syndrome.

Mycoses of the Hair, Nails, and Skin

• Dermatophytoses: Fungal infections affecting skin, hair, and nails, commonly known as ringworm or athlete's foot.
  • Treated with topical antifungal medications, and more severe cases may require oral antifungals.
• Candidiasis:
  • Caused by Candida albicans, leading to superficial infections and potential systemic complications if untreated.
  • Treated with antifungal medications like Nystatin and Fluconazole.