Chapter 19 Eye and Skin Infections PDF

Chapter 19 Eye and Skin Infections • Epidermis vs Dermis: • • Epidermis: • Superficial layer. • Composed of five sublayers of epithelial cells. • Secretes waterproofing substances to prevent water loss. • Stratum corneum is made of dead keratinocytes. Dermis: • Deeper layer. • Contains...

Chapter 19 Eye and Skin Infections • Epidermis vs Dermis: • • Epidermis: • Superficial layer. • Composed of five sublayers of epithelial cells. • Secretes waterproofing substances to prevent water loss. • Stratum corneum is made of dead keratinocytes. Dermis: • Deeper layer. • Contains connective tissue, blood vessels, nerves, hair follicles, and sweat glands. Different Types of Skin Rashes: • Classification: • Macular: flat/red, less than 1cm in diameter. • Papular: small, solid, and elevated. • Pustular: papule filled with pus. • Maculopapular: reddened papule. • Vesicular: small blisters. Causes of Skin Rashes: • • Infectious Causes: • Exanthem: widespread with systemic symptoms. • Enanthem: mucous membranes. • Caused by reactions to toxins produced by infectious agents: reaction to organism, physical damage to the skin, host immune response Non-Infectious Causes: • Result from allergies. Mucous Membranes: • Definitions: • Called mucosae or mucosa. • Epithelial linings serving as a protective barrier. • Found in the GI and urogenital tract. • Continuous with the skin in several places. • Not all produce mucus. Viral Diseases of the Skin: Chickenpox: • Agent: Varicella-Zoster virus (VZV). • Transmission: Inhalation of infected particles from skin lesions. • Target Cells: Capillary endothelial cells and the deepest layer of the epidermis. • Pathogenesis: Initial exposure causes chickenpox, remains latent, re-emerges later causing shingles. • Disease: Rash with maculopapules, vesicles, pustules, and scabs. • Treatment: Acyclovir for shingles; Varicella vaccination. Smallpox: • Agent: Variola virus. • Transmission: Direct or indirect contact. • Target Cells: Lymph nodes, lymphoid organs, internal organs, bone marrow. • Pathogenesis: Two sequential viremias, oral mucosa spots progress to pox pustules on the skin. • Treatment: No FDA-approved treatment; vaccination was historically used. • Note: Eradicated from the population in 1979. Bacterial Diseases of the Skin: Staphylococcus spp.: • Agents: S. aureus, S. epidermidis. • Transmission: S. aureus found in the nose, gaining access to dermis via cuts. • Pathogenesis: Coagulase promotes abscess formation; exotoxins cause damage to host tissue and weaken host defenses; MRSA is antibiotic-resistant. • Diseases: Folliculitis (superficial), furuncle (boil, deep), carbuncles (boils joined together), toxic shock syndrome, scaled-skin syndrome. • Treatment: Surgical drainage, antibiotics (vancomycin for MRSA). Streptococcus pyogenes: • Agent: S. pyogenes. • Transmission: Natural reservoirs in nasopharynx and skin. • Pathogenesis: Causes necrotizing fasciitis(flesh eating bacteria); virulence factors include capsule, M protein, streptolysins, exotoxins. • Disease: Necrotizing fasciitis; incidence rising due to NSAID use. • Treatment: Antibiotics (metronidazole); increasing antibiotic resistance. • Note: Causes beta hemolysis on blood agar because they use streptolysins to lyse red blood cells. Mechanism of virulence. Also use capsules, pilus like M protein(binds complement), lipoteichoic acid (adhesion), peptidoglycan (cause inflammation) • Also note that the incidence of necrotizing fasciitis is rising due to increase in the use of NSAIDs which increase your susceptibility to infection by S. pyogenes Fungal Diseases of the Skin: Tinea spp. • Agents: Epidermophyton, Trichophyton, Microsporum (dermatophytes). • Transmission: Typically from contact with infected skin or surfaces. • Target Cells: Infect cool, moist, keratinized tissues (hair follicles, skin, nails). • Pathogenesis: Dermatophytes infect keratinized tissues, leading to diseases like tinea capitis, corporis, cruris, pedis, and unguium. • Disease: Named after the location of infection (e.g., tinea capitis on the scalp, tinea pedis on the foot, tinea corporis on the body). • Treatment: Antifungal medications such as imidazole or clotrimazole. Candida albicans • Agent: Candida albicans (dimorphic yeast). • Transmission: Normal flora in the body, common in GI tract, oral cavity, and skin. • Target Cells: Skin, mucous membranes, and body organs. • Pathogenesis: Causes candida intertrigo, especially where skin rubs together. • Disease: Named after the condition, candida intertrigo. • Diagnosis: Clinical appearance, microscopic examination (KOH preparations), culturing on Sabouraud agar. • Treatment: Antifungal medications like imidazole or clotrimazole. Anatomy of the Eye: • External Parts: Eyelids, cornea, lens, iris, pupil, sclera. • Conjunctiva: Covers external parts (moist, transparent mucous membrane). • Internal Parts: Retina, macula (center of retina), vitreous humor (maintains shape of eye). • Neuronal Tissue: Lines the inside of the eye, originates from the optic nerve. Eye Infections: Herpes Zoster Ophthalmicus • Cause: Reactivation of herpes zoster virus. • Transmission: Along the ophthalmic division of the trigeminal nerve. • Symptoms: Vesicular lesions on the forehead, eyelids, nose, and eye; corneal inflammation, eye pain/sensitivity. • Treatment: Oral antiviral medications like acyclovir and valacyclovir. Inclusion Conjunctivitis (Chlamydia trachomatis) • Agent: Chlamydia trachomatis. • Transmission: Newborns during birthing process. • Symptoms: Self-limiting infection in newborns; can cause trachoma, leading to pebbled conjunctiva and inward-turning eyelashes in adults. • Treatment: Antibiotics eyedrops (erythromycin) for newborns; oral antibiotics (azithromycin) and topical tetracycline for trachoma. Fungal Keratitis • Cause: Species of Fusarium, Aspergillus, and Candida. • Transmission: Typically occurs after eye injury, wearing contact lenses, or foreign body abrasion. • Diagnosis: Fungal culture, PCR amplification, or confocal microscopy. • Treatment: Systemic therapy (oral or intravenous medications) or surgery for invasive lesions; antifungal medications like natamycin or Amphotericin B for superficial lesions. CASE STUDIES CHICKEN POX AND SHINGLES • • Background: • Agent: Varicella-Zoster virus (VZV). • Initial Exposure: Causes chickenpox. • Latency: Virus remains latent in dorsal root ganglia. • Re-emergence: Can cause shingles later in life. Clinical Presentation (Chickenpox): • Contracted by inhaling infected particles. • • • Prodromal symptoms absent in children. • Itchy rash with maculopapules, vesicles, pustules, and scabs. Clinical Presentation (Shingles): • Re-emergence of VZV causes more severe symptoms than chickenpox. • Usually occurs in older individuals. • Diagnosed clinically; antibody and DNA tests available. Treatment: • Acyclovir (antiviral) for shingles or severe chickenpox. • Varicella vaccination for prevention. CASE STUDY: NECROTIZING FASCIITIS: STREPTOCOCUSS PYOGENES Background: • • • Patient Injury: Minor cut and injury to the left side of the body. • Day 2 Symptoms: Vomiting, diarrhea, fever, severe pain, bruising. • Day 3 Symptoms: Difficulty breathing, vision impairment, leaking fluid and blood. Hospital Diagnosis and Treatment: • Diagnosis: Necrotizing fasciitis. • Septic Shock: Patient admitted in septic shock. • Treatment: Vasopressors to raise blood pressure, surgical removal (7% of body surface), delayed skin grafting. Follow-up: • Complications: Gangrene in fingers and lower extremities due to continued vasopressor use. • Recovery: After 3 months and multiple amputations. CASE STUDY: STAPHYLOCOCCAL SCALDED SKIN SYNDROME Patient Information: • Patient: 3-month-old baby. • Health Status: Generally healthy but experiences frequent diaper rashes. Symptoms: • Day 1: • Red skin and small, painful, bubbly blisters around the diaper area. • Day 2: • Redness running down legs, crusted blisters, skin sloughs off when wiped. • Accompanied by fever. Culture and Gram-stain Results: • • Culture Results: • Blood + skin cultures negative. • Nasal abscess swab positive. • Subcultures positive on blood agar and mannitol salt agar. • Alpha toxin present on blood agar. Gram-stain Results: • • Gram-positive staphylococci identified. Tube Coagulase Results: • Positive for coagulase. Diagnosis: • Presumptive Identity: Staphylococcus aureus. • Coagulase: A. exoenzyme. Treatment: • Diagnosis: Staphylococcal scalded skin syndrome (SSSS). • Kirby-Baurer Assay: Determines antibiotic susceptibility, identified as a strain of MSSA. • Treatment: IV nafcillin. Additional Information: • Exfolitatin Exotoxin: Causes red skin appearance, acts as a protease and superantigen. • Superantigen: C. causes an overreaction of the immune system. ST ANTHONY’S FIRE: SHINGLES Patient Information: • Patient: 69-year-old man. • Health Status: Type 2 diabetic. Symptoms: • Tingling sensation from spine to middle of ribcage. • Severe pain the next morning. • Small blisters forming a line along the skin. • Red skin. Diagnosis: • Disease: St. Anthony’s fire. • Cause: Same virus that causes chickenpox. Treatment: • Antiviral and pain relief medications. • Close monitoring of blood sugar levels. Follow-up: disease clarification: shingles