infectious-diseases

Skin Infections

1. Structure of the Skin

• Composes the cutaneous membrane and accessory structures.

  • Cutaneous Membrane:

    • Epidermis: Stratified squamous epithelium.

    • Dermis:

      • Papillary Layer: Areolar tissue.

      • Reticular Layer: Dense irregular connective tissue.

    • Hypodermis: Subcutaneous layer, separates integument from deeper organs; not part of integument.

  • Accessory Structures: Hair shafts, sweat glands (duct and gland types), sebaceous glands, nerves, arteries, and veins connected by the cutaneous plexus.

2. Natural Defenses of the Skin

• Keratin: Provides a waterproof barrier.

• Skin Sloughing: Removes pathogens.

• Sebum:

  • Low pH and high lipid content inhibit microbial growth.

• Sweat:

  • Low pH, high salt; contains lysozyme which digests peptidoglycan.

3. Normal Skin Flora

• Key contributors include:

  • Propionibacterium acnes

  • Corynebacterium sp.

  • Staphylococci:

    • Staphylococcus epidermidis

    • Staphylococcus aureus

  • Streptococci sp.

  • Candida albicans (yeast)

4. Bacterial Infections

Types of Bacteria

• Single-Celled Micro-organisms: Varieties include spherical, doublets, and spirochetes.

• Staphylococcus:

  • Gram-positive, appears in clumps in skin and respiratory tract.

• Streptococcus:

  • Chain bacteria associated with systemic disease and skin infections.

• Bacillus:

  • Spore-forming, aerobic, causes systemic damage.

5. Impetigo Contagiosa & Erysipelas

• Etiology: Caused by A-beta-hemolytic streptococci, S. aureus, or both; spreads through close contact.

• Symptoms:

  • Mild itching, small vesicles, and pustules that rupture and crust, often in body folds.

• Management:

  • Cleansing, topical antibacterial agents, systemic antibiotics.

6. Furunculosis (Boils)

• Etiology: Infection of hair follicle, usually due to staphylococcus.

• Signs and Symptoms:

  • Pustule enlarges, redness, tenderness increases with pressure, may rupture.

• Management:

  • Protect from irritation, physician referral for antibiotics.

7. Carbuncles

• Etiology: Similar to furuncles, larger and deeper lesions.

• Symptoms:

  • Fever and WBC elevation; moisture discharge from openings.

• Management:

  • Surgical drainage and antibiotics; warm compresses.

8. Folliculitis

• Etiology: Inflammation of hair follicle from infectious/non-infectious agents.

• Signs and Symptoms:

  • Redness around follicle, papule or pustule formation, crusting, possible scarring.

• Management:

  • Moist heat, antibiotics if necessary.

9. Hidradenitis Suppurativa

• Etiology: Inflammation leads to blockage of the apocrine gland.

• Signs and Symptoms:

  • Small papules evolve into deep dermal inflammation.

• Management:

  • Avoid irritants, medicated soaps, systemic antibiotics.

10. Acne Vulgaris

• Etiology: Inflammatory disease involving hair follicles and sebaceous glands; influenced by hormones.

• Signs and Symptoms:

  • Whiteheads, blackheads, papules, pustules, cysts; potential for scarring.

• Management:

  • Topical/systemic treatments; mild soaps recommended.

11. Nail Disorders

• Types of abnormalities include:

  • Anonychia congenita

  • Pitting (Psoriasis)

  • Onycholysis (Tinea)

  • Clubbed nails (hypoxia)

12. Necrotizing Fasciitis

• Etiology: Caused by Streptococcus pyogenes.

• Signs and Symptoms:

  • Rapidly spreading cellulitis; may require limb amputation.

• Management:

  • Surgical removal and antibiotics; high mortality risk.

13. Hansen's Disease: Leprosy

• Causative Agent: Mycobacterium leprae.

• Signs and Symptoms:

  • Change in pigmentation, numbness; slow progression.

• Management:

  • Long-term drug treatment is necessary.

14. Viral Infections

• Herpes Simplex Virus: Involves various forms including labialis and zoster; presents as vesicular lesions with sensitivity.

• Management for Herpes: Pain reduction, antivirals to shorten outbreak.

15. Measles and Rubella

• Measles: Highly contagious with characteristic skin rash; vaccine-preventable.

• Rubella: Mild rash but serious for developing fetuses; preventable with vaccine.

16. Tinea Infections

• Tinea Capitis (Scalp): Manage with systemic antifungals; spreads easily.

• Tinea Pedis (Athlete's Foot): Most common; treat with antifungal agents and hygiene.

17. Candidiasis (Moniliasis)

• Etiology: Yeast fungus thriving in humid conditions; leads to red patches in body folds.

• Management: Keep areas dry; use antifungal treatments.