Skin and Eye Infections

What are the main anatomical layers/features of the skin?

• Epidermis

• Dermis

• Sebaceous glands

• Immune cells (Langerhans cells, mast cells, macrophages)

What are Langerhans cells?

Antigen-presenting cells in the epidermis

What do sebaceous glands produce?

Sebum (oily substance)

Does skin microbiota vary or stay the same across the body?

Varies by body site

Name common skin microbiota organisms

• Corynebacterium

• Cutibacterium

• Staphylococcus epidermidis

Which skin areas have the MOST microbial diversity?

Sebaceous and moist areas

Which areas have the LEAST diversity?

Dry areas

What are antimicrobial peptides?

Positively charged molecules that disrupt bacterial membranes

How does sebum protect the skin?

Low pH + lipids inhibit microbial growth

How does sweat act as a defense?

Low pH + high salt inhibits microbes

What does lysozyme do?

Breaks down bacterial cell walls (peptidoglycan)

What type of bacteria is Staphylococcus aureus?

Gram-positive cocci in clusters

Where is Staphylococcus aureus normally found?

Skin and anterior nares

What is MRSA?

Methicillin-resistant Staphylococcus aureus

What type of infections does S. aureus cause?

Suppurative (pus-forming), localized infections

Who is high risk?

Diabetics, burn patients, neonates

What is a furuncle?

Boil from infected hair follicle

What is a carbuncle?

Deep cluster of boils (abscess)

What is impetigo?

Superficial, contagious skin infection with blisters

What is cellulitis?

Spreading infection of connective tissue (non-pus)

What causes scalded skin syndrome?

Exfoliating toxins

What causes toxic shock syndrome (TSS)?

TSST-1 superantigen → cytokine storm

How is S. aureus diagnosed?

Culture (SBA), agglutination test, PCR

How is mild infection treated?

Oral antibiotics

Severe infection?

IV antibiotics ± surgical debridement

How is S. aureus infection prevented?

Hygiene, wound care, hospital screening for MRSA

Carbuncle vs impetigo vs cellulitis?

• Carbuncle: deep, pus-filled abscess

• Impetigo: superficial, crusty lesions

• Cellulitis: diffuse spreading infection, no pus

Cause of measles?

Virus

Transmission of measles?

Respiratory droplets (very contagious)

Key symptom of measles?

Koplik spots + rash from head downward

Prevention of measles?

MMR vaccine

Causes of Rubella?

Virus (Rubivirus)

Why is Rubella dangerous?

Birth defects in fetus

What are the characteristics of a Rubella rash?

Mild, 3-day rash

Causes of Fifth Disease?

Parvovirus B19

What is a classic sign of Fifth Disease?

“Slapped cheek” rash

What is a treatment of Fifth Disease?

None (self-limiting)

Causes of Roseola?

HHV-6

What are unique features of Roseola?

High fever THEN rash

Causes of Impetigo?

Staph aureus + Strep pyogenes

What is the appearance of impetigo?

Honey-colored crust

How is impetigo transmitted?

Direct contact

What is a treatment of impetigo?

Antibiotics

Causes of cellulitis?

Strep pyogenes ± Staph aureu

What are symptoms of cellulitis?

Red, warm, swollen skin

What is a treatment for cellulitis?

Oral or IV antibiotics

Cause of chicken pox?

Virus (HHV-3)

What are the charactersitics of a chickenpox rash?

Vesicles → crust

How can you prevent chickenpox?

Vaccine

What causes small pox?

Virus

What is the severity of small pox?

High mortality, eradicated

How is smallpox transmitted?

Droplets, fomites

Cause of Leishmaniasis?

Parasite

How is Leishmaniasis transmitted?

Sand fly

How is Leishmaniasis prevented?

Avoid vector

What is the cause of cutaneous anthrax?

Bacillus anthracis (bacteria)

What is a key sign of cutaneous anthrax?

Black eschar

What causes Ringworm?

Dermatophyte fungi

How is ringworm transmitted?

Direct/indirect contact

Causes of Tinea versicolor?

Malassezia (yeast)

Characteristics of Tinea versicolor

Cosmetic skin discoloration

What is the conjunctiva?

Membrane covering eye and eyelids

What is the cornea?

Transparent outer layer (“windshield”)

What is the eye’s main defense?

Tears

What do tears contain?

Lysozyme + lactoferrin

Why are eye defenses limited inflammation?

To preserve vision

Common eye microbiota?

Corynebacterium

Neonatal causes?

Neisseria gonorrhoeae, Chlamydia trachomatis

What is bacterial symptom of conjunctivitis?

Thick discharge

What is a viral symptom of conjunctivitis?

Watery discharge

What is a treatment for connjunctivitis?

Ciprofloxacin

What are cause of keratitis?

Bacteria, HSV-1, amoeba

What are risk factors of keratitis?

Contact lenses

What are complications of keratitis?

Blindness

What is a treatment of keratitis

Acyclovir or trifluridine