Measles Case Study Quiz

Chapter 19: Infections of the Skin and Eye

• Chapter Objectives:
  • Correlate skin and eye anatomy/physiology to infectious processes.
  • Differentiate viral, bacterial, and parasitic skin/eye infections by symptoms.
  • Relate pathogens' mechanisms to disease prevention strategies.
  • Connect pathogen physiology to antimicrobial treatment/prevention.

Rash Ruins Vacation Scenarios

• Scenario 1 (Nate):

  • 69-year-old type 2 diabetic.
  • Awakened with a tingling sensation extending from the spine to the rib cage.
  • Discomfort worsened to severe pain.
  • Developed small blisters along irritated red skin.
  • Referred to a local doctor by hotel.

• Scenario 1 (Diagnosis):

  • Diagnosed with St. Anthony's fire (shingles).
  • Caused by the same virus (VZV) that causes chickenpox.
  • VZV had previously nested in a spinal nerve root.

• Scenario 1 (Treatment):

  • Prescribed antiviral and pain relief medication.
  • Instructed to maintain good blood sugar control.
  • Advised to follow up with a regular physician.

• Scenario 1 (Follow-Up):

  • Trip to Italy cut short.
  • Diagnosis and treatment plan confirmed in the U.S.
  • St. Anthony's fire is another name for shingles.

• Scenario 1 (Resolution):

  • Recovered from shingles.
  • Received antiviral medication and rest.
  • Able to return to Italy for a successful later trip.

19.1 Anatomy of Skin and Eye

• Section Objectives:

  • List skin cell components and functions.
  • Describe dermis/epidermis structural differences/similarities.
  • Describe skin's role in disease prevention.
  • Distinguish between eye's internal/external parts.

• Skin (General):

  • Largest human organ (16-22 sq ft).
  • Acts as a barrier, preventing microbial access to deeper tissues.

• Skin Layers:

  • Superficial layer (epidermis): 5 layers of dead keratinocytes.
  • Deep layer (dermis): connective tissue, cells (blood vessels, nerves, hair follicles, sweat glands).

• Eye Structure (External):

  • Eyelids, Cornea, Lens, Iris, Pupil, Sclera.

• Eye Structure (Internal):

  • Retina, Macula, Vitreous humor.

19.2 Viral Infections of the Skin

• Section Objectives:
  • Classify viruses causing skin rashes by genomic structure.
  • Explain viral skin infection sequelae pathogenesis.
  • Diagnose viral skin infections based on patient signs/symptoms.
  • Recommend treatment/prevention options for viral skin infections.

19.3 Bacterial Infections of the Skin

• Section Objectives:
  • Name bacterial pathogens causing common skin infections.
  • Categorize skin infections by bacterial physiology.
  • List clinical/laboratory methods of diagnosing bacterial skin infections.
  • Develop treatment/prevention plans for bacterial skin infections.

Staphylococcal Skin Infections

• Staphylococcus aureus:

  • Normal inhabitant of the nose.
  • Causes skin infections.
  • Can lead to superficial or deep infections (folliculitis, furuncle, carbuncles).
  • Produces enzymes (coagulase) hindering immune system response.
  • Produces Exotoxins:
    • Toxic shock syndrome toxin (TSST) causing Toxic shock syndrome.
    • Exfoliative toxin causing scalded skin syndrome.

• Methicillin-resistant S. aureus (MRSA):

  • Resistant to methicillin.
  • Commonly found in hospitals but becoming more common in the community.
  • Vancomycin is the treatment of choice.

Streptococcal Skin Infections

• Streptococcus pyogenes (GAS):

  • Inhabits human nasopharynx and skin.
  • Causes Necrotizing fasciitis ("flesh-eating" disease).
  • Produces Exotoxins:
    • SPEs, which trigger massive inflammation and shock.
  • Infections can sometimes be polymicrobial.

• Rheumatic fever:

  • Develops after a primary GAS infection.
  • Autoreactive antibodies against cardiac antigens damage tissues.

• Acne vulgaris:

  • Affects 60-70% of Americans.

  • Results from blocked hair follicles (comedones)

  • Common types include; Open comedones (blackheads), Closed comedones (whiteheads). Inflammatory acne, cystic acne.

  • Factors contributing; Genetics, Hormones, And Gram-positive bacteria Propionibacterium acnes.

  • P. acnes metabolises sebum and leads to inflammation.

19.4 Fungal Infections of the Skin

• Section Objectives:
  • Outline common fungal skin infections by etiology.
  • Compare dermatophytes to other fungi infecting skin.
  • Explain how common fungal infections are clinically diagnosed.

Fungi

• Dermatophytes:

  • Epidermophyton, Trichophyton, Microsporum.
  • Infects skin, hair, nails.
  • Tinea capitis (scalp), Tinea corporis (body), Tinea cruris (jock itch), Tinea pedis (foot), Tinea unguium (nails).

• Tinea versicolor:

  • Caused by *Malassezia *.
  • Characterised by hypopigmented lesions (lighter coloration).
  • Common in warm, humid climates.

• Candida:

  • Dimorphic yeasts.
  • Part of the body's normal flora.
  • Can infect skin, mucous membranes, and other organs.
  • Can cause inflammation and skin irritation.

19.5 Skin Infections of Special Circumstances

• Not included (in this chapter)

19.6 Eye Infections

• Section Objectives:
  • Identify viral, bacterial, and fungal eye infection causes.
  • Describe pink eye (conjunctivitis) symptoms/etiology.
  • Explain the pathogenesis of infectious keratitis/endophthalmitis differences.
  • Outline the corneal epithelium's relationship to fungal keratits.

Viral Eye Infections

• Herpes viruses:
  • Major cause of keratitis/keratoconjunctivitis.
  • Herpes Simplex 1 (HSV-1) causing most cases.
  • Lesions might not cause damage at first but reactivation leads to damage/blindness.
  • Treated with antiviral medications (acyclovir, trifluridine).
  • Herpes zoster ophthalmicus:
    • Shingles outbreak in the ophthalmic division of the trigeminal nerve.
    • Painful and can also affect eyes.
    • Treated with antiviral medications.

Bacterial Eye Infections

• Bacterial conjunctivitis:

  • Affects one eye.
  • Acute, painful, purulent.
  • Caused by pyogenic bacteria (like Staph/Strep) leading to irritation and discharge.
  • Can be identified and treated accordingly.

• Chlamydia trachomatis:

  • Obligate intracellular bacteria.
  • Can cause infection through vaginal contact.
  • Infants are often treated at birth to avoid potential for eye infections.
  • Often affects the conjunctiva.

• Trachoma:

  • Most common cause of infectious blindness worldwide.
  • Often transmitted by direct eye contact.
  • Can cause the eyelashes to turn inward (trichiasis).
  • Irritates and potentially scars the cornea.

• Neisseria gonorrheae:

  • Causes ophthalmia neonatorum (eye infection in newborns).
  • Transmitted during birth from an infected mother.

Fungal and Parasitic Eye Infections

• Fungal keratitis:

  • Caused by fungi (Fusarium, Aspergillus, Candida).
  • Often originates in environments such as; warm, humid; or from compromised areas.
  • Diagnosis requires; Culturing the fungi, Polymerase Chain Reaction (PCR), and Confocal microscopy.
  • Frequently requires systemic treatment (antifungals like Natamycin or Amphtericin B).

• Parasitic keratitis:

  • Due to Acanthamoeba species (protozoa).
  • Often found in environments with stagnant water or air conditioning systems.
  • If left untreated eye may become progressively irritated and damaged along with potential loss of vision.

Test your knowledge on the key details of Moyo's case study regarding a measles epidemic. This quiz covers Moyo's diagnosis, vaccination status, and health officials' responses. Challenge yourself to recall significant facts from the scenario presented.