skin & eye disease

Microbial Diseases of the Skin & Eyes

Bacterial Diseases of the Skin & Eyes
Trachoma
  • Causative agent: Chlamydia trachomatis
    • Classification: Gram negative bacterium (cocciod)
  • Transmission: Direct or indirect contact with eye, throat, or nasal secretions
  • Prevalence: >80,000,000 cases worldwide annually
Infection & Symptoms
  • C. trachomatis colonizes beneath the eyelid upon introduction
  • Causes inflammation, producing swollen lumps beneath eyelids with discharge
  • Repeated infections lead to:
    • Photosensitivity
    • Trichiasis (inward turning eyelashes)
    • Corneal abrasion
    • Scarring of cornea
  • Untreated can lead to blindness
  • Mortality: Nonfatal, but major cause of infectious blindness
Treatment & Prevention
  • Diagnosis: Specialized tests (McCallan’s Classification) and symptom recognition
  • Treatment: Antibiotic eye drops (azithromycin), surgery for trichiasis
  • Prevention: Sanitation, personal hygiene, and community prophylaxis
Necrotizing Fasciitis
  • Causative agent: Streptococcus pyogenes
    • Classification: Gram positive bacterium (cocci)
  • Transmission: Parenteral introduction via skin injury
  • Prevalence: >1,000 cases worldwide annually
Infection & Symptoms
  • Enters through injury; produces toxins and hemolysins
  • Causes inflammation and rapid tissue destruction, leading to necrosis
  • Early Symptoms: Skin discoloration, breaks, shiny appearance
  • Mortality: >40% with delayed treatment (sepsis, septic shock)
Treatment & Prevention
  • Diagnosis: Recognition of early symptoms
  • Treatment: Broad-spectrum antibiotics, surgical debridement, excision, amputation
  • Prevention: Proper wound care, sanitation, and timely medical visits
Methicillin-Resistant Staphylococcus aureus (MRSA)
  • Causative agent: Staphylococcus aureus
    • Classification: Gram positive bacterium (cocci)
  • Transmission: Direct contact with bodily fluids; parenteral introduction
  • Prevalence: >80,000 cases worldwide annually
Infection & Symptoms
  • Survives on skin surfaces due to slime layer
  • Rapid growth leads to blistering, pustules, folliculitis, furuncles, impetigo, and toxic shock
  • Mortality: >13% (due to sepsis, toxic shock); 11,000 deaths annually
Treatment & Prevention
  • Diagnosis: Gram stain and culture on differential medium
  • Treatment: Antibiotics (vancomycin), drainage of lesions, removal of dead tissue
  • Prevention: Isolation of infected patients, handwashing, sanitation
Fungal Diseases of the Skin & Eyes
Dermatophytosis
  • Causative agents: Trichophyton spp., Microsporum spp., or Epidermophyton spp.
    • Classification: Fungi (molds)
  • Transmission: Indirect contact in warm, moist environments
  • Prevalence: >20% of adults worldwide
Infection & Symptoms
  • Fungal hyphae grow beneath the skin, causing inflammation
  • Symptoms include itchy, red rings; scaliness; oozing or blistering
  • Conditions include:
    • Tinea capitis (scalp)
    • Tinea cruris (groin)
    • Tinea pedis (feet)
    • Tinea unguium (nails)
  • Mortality: Nonfatal
Treatment & Prevention
  • Diagnosis: Visual examination, differential diagnostics through culturing
  • Treatment: Antifungals (clotrimazole)
  • Prevention: Hygiene, proper footwear, avoiding sharing personal items
Sporotrichosis
  • Causative agent: Sporothrix schenkii
    • Classification: Fungi (dimorphic)
  • Transmission: Via parenteral route (thorn punctures)
  • Prevalence: 250 cases annually worldwide
Infection & Symptoms
  • Spores enter through skin injuries, developing into yeast form
  • Creates pain-free lesions; can lead to disseminated infections in severe cases
  • Systemic Symptoms: Respiratory (coughing, cavitation), circulatory (ulcerative lesions), systemic (fibrosis, weight loss)
  • Mortality: <0.1% (meningitis or encephalitis)
Treatment & Prevention
  • Diagnosis: Culture of spores from skin or sputum
  • Treatment: Antifungals (potassium iodide, amphotericin B)
  • Prevention: Wound cleaning, sanitation, protective clothing when handling plants
Viral Diseases of the Skin & Eyes
Chickenpox
  • Causative agent: Varicella zoster virus
    • Classification: Group I enveloped icosahedral virus
  • Transmission: Droplet transmission
  • Prevalence: Common in children worldwide
Infection & Symptoms
  • Virus enters through inhalation, reaching the dorsal ganglia
  • Systemic symptoms: Fever, headache, malaise; skin symptoms: rashes and blisters
  • Mortality: <0.1%, increased risk with age
Treatment & Prevention
  • Diagnosis: Observation of symptoms
  • Treatment: Acyclovir, trimming nails to prevent scratching
  • Prevention: Varicella vaccine
Shingles
  • Causative agent: Varicella zoster virus (reactivation)
    • Classification: Group I enveloped icosahedral virus
  • Transmission: Droplet transmission and reactivation
  • Prevalence: 1,000,000 cases annually
Infection & Symptoms
  • Reactivation leads to severe skin and systemic symptoms: headache, fever, pain, rashes
  • Mortality: <0.1% (increased with age)
Treatment & Prevention
  • Similar treatment and prevention strategies as chickenpox, with zoster vaccine recommended
Mpox
  • Causative agent: Monkeypox virus
    • Classification: Group I enveloped “dumbbell” virus
  • Transmission: Direct contact with infected fluids or animals
  • Prevalence: >80,000 cases annually worldwide
Infection & Symptoms
  • Systemic symptoms: fever, headache, muscle pain; skin lesions develop and change coloration
  • Mortality: >10% (due to complications)
Treatment & Prevention
  • Diagnosis: Symptoms observation, PCR testing
  • Treatment: Antivirals (tecovirimat)
  • Prevention: Smallpox vaccine, avoiding wild mammals and infected fluids
Smallpox
  • Causative agent: Variola minor virus
    • Classification: Group I enveloped “dumbbell” virus
  • Transmission: Droplet transmission
  • Prevalence: Eradicated!
Infection & Symptoms
  • Symptoms include fever, malaise, and skin pustules
  • Mortality: 30 – 100% (varies with severity)
Treatment & Prevention
  • Diagnosis: Recognition of symptoms; Guarnieri bodies
  • Treatment: Fluid therapy, ventilation assistance
  • Prevention: Smallpox vaccine
Parasitic Diseases of the Skin & Eyes
Loiasis
  • Causative agent: Loa loa
    • Classification: Helminth (roundworm)
  • Transmission: Bite from Chrysops sp. deer fly
  • Prevalence: >3,000,000 cases annually worldwide
Infection & Symptoms
  • Microfilariae enter blood, migrating to eyes
  • Symptoms: Angioedema, muscle pain, blurred vision, potential blindness
  • Mortality: Nonfatal
Treatment & Prevention
  • Diagnosis: Identification of microfilariae in blood
  • Treatment: Anthelminthic (diethylcarbamazine)
  • Prevention: Insect repellents, protective clothing