Lecture 28 - Skin and Eye Diseases

Epidermis

dry, squamous epithelial cells, sheds

dermis

contains blood vessels, nerves, muscles, glands, hair follicles

skin damage

can be localized or a systemic infection -> when microbe invade through the blood vessels

crust (lesions)

dried blood

cysts (lesions)

close fluid sacs filled with fluid/material

macule (lesions)

spots on the skin

papule (lesions)

raised solid bumps

pustule (lesions)

pus filled bumps

ulcer (lesions)

open sores that come with tissue loss

vesicle (lesions)

fluid filled blisters

Common eye infection sites

Conjuctiva: conjuctivitis

eyelids: blepharitis

cornea: keratitus

lacrimal sac: dacryocysititis

conjuctiva

mucous membrane over the eyeball

viterous humor

sterile, gel/watery substance inside the eye

nasolacrimal system

Produces and drains tears

Staphylococcus aureus

• Diseases: Folliculitis, furuncles (boils), carbuncles, SSSS (scalded skin)

• Virulence: Staphylolysins, protein A

• Transmission: Skin contact, cuts

Streptococcus pyogenes

• Disease: Necrotizing fasciitis ("flesh-eating disease")

• Virulence: M protein, proteases, exotoxins

• Treatment: Surgical removal, amputation

Pseudomonas aeruginosa

• Diseases: Hot tub rash, swimmer’s ear

• Virulence: Pyocyanin, biofilm-forming

• Treatment: Polymyxin B, fluoroquinolones

• gram negative

Cutibacterium acnes

• Aerobic, gram positive

• Exposure: is an opportunistic invader of follicles

• Acne relations: clogged hair follicles, comedones - black/white head pimples

• Virulence: secretes lipases to breakdown sebum into inflammatory fatty acids, chemokines (sebum)

• Infection relations: several types of skin lesions, acne

• Treatment: depends on grade (salicylic acid, antibiotic creams, strong medicines) <- low to high

Haemophils influenzae

• Gram negative 

• Exposure: respiratory droplets - highly contagious

• Virulence: attachment pili, igA proteases to degrade antibodies, lipo-oligosaccharides (LOS) 

• Infection relations: bacterial conjunctivitis, green/white/yellow discharge at eye

• Treatments: broad spectrum topical antibiotics

HPV

• Exposure: direct skin-skin contact, broken skin

• Virulence: provirus, E6 & E7

• Infection relations: warts - plantar, flat, filiform, genital (the infection targets keratinocytes and messes with their proliferation)

  • Virus also inactivates tumor suppressor proteins using a specific set of proteins, will evade the immune system by restricting cell communication and MHC1 molecule (recognition)

• Treatments: typically required - liquid nitrogen & salicylic acid but there are many options out there

HSV-1

• Exposure: direct oral contact, any mucous membrane, highly contagious

• Virulence: basal keratinocytes, the virus has a set of glycoproteins that mediate the attachment to keratinocytes

• Infection relations: cold sores, fever blisters, latency in neurons - specifically trigeminal nerve

• Treatments: no cure, acyclovir, topical meds

adenovirus

• Exposure: very contagious secretions (transferable), seen with a common cold

• Virulence: fiber proteins

• Infection relations: viral conjunctivitis, watery discharge not pus, redness and irritation

• Treatments: no effective treatment

dermatophytes

• Exposure: direct contact

• virulence/infection relations: keratinases to destroy keratinocytes, lipases, proteases to penetrate skin

• Disease relations: tineas/ringworm, athletes foot, barber's itch, jock itch

• Treatments: diagnose with wood lamp to identify fluorophores & and microscopy, treat with antifungal topical and oral treatments

• ~Subcutaneous fungal skin infections: deeper than surface level skin for below

sporothrix schenckii

• (rose gardener’s disease)

  • Subcutaneous fungal skin infections: deeper than surface level skin for below. Invades the lymph system and forms ulcers/nodules that spread through the lymph and convert from mold to yeast, then starts producing melanin to protect itself from oxidative damage

  • Exposure: soil, plants, timber, wound

  • Virulence: melanin, thermotolerance

  • Infection: skin ulcers, to lymph system and beyond

  • Treatments: wear PPE when working in the garden, identify presence via culturing and microscopy, treat with itraconazole 

acanthamoeba

• Exposure: soil, unchlorinated fresh water

• Virulence: proteases, phospholipases - resistant to antimicrobials bc its protozoa

• Infection relations: skin ulcers, nodules, abscesses, and eye pain/irritation/sensitivity/blindness - can cause respiratory infection in immunocompromised patients

• Treatments: difficult. Intensive early application of topical antiseptics, avoid exposure, practice hygiene with contacts

• Diagnosis made by scraping cornea for a microscopy