Module Seven: Skin and Eye Infections

This set covers Module 7 lecture notes detailing bacterial, viral, and fungal skin infections, as well as various bacterial, viral, and parasitic eye infections.

Epidermis

The upper or superficial part of the skin composed of stratified squamous epithelium.

Stratum corneum

The outer layers of the epidermis composed of dead keratinized cells that are constantly shed.

Dermis

The layer beneath the epidermis composed of connective tissue that is vascular and contains nerves and glands.

Pseudoriferous glands

A term for sweat glands found in the dermis.

Sebaceous glands

Glands associated with hair follicles that produce sebum or oil.

Hypodermis

The layer beneath the dermis containing connective tissue, fatty tissue, and a blood supply.

Skin pH

A factor that makes the skin a hostile environment for many organisms, with a low pH around $5$.

Staphylococcus aureus

A gram-positive cocci bacterium that produced virulence factors to invade and establish infections in humans.

Staphylolysins

A form of hemolysis that kills skin cells and white blood cells, contributing to the formation of pus.

Coagulase

A clotting protein produced by staph that is involved in abscess formation; staph is coagulase positive.

Leukocidins

Virulence factors that kill white blood cells and contribute to pus formation.

Toxic shock syndrome toxin (TSST)

An exotoxin and superantigen that can induce fever, diarrhea, vomiting, heart failure, and desquamation.

Desquamation

The exfoliation or shedding of the outer layers of skin cells.

Folliculitis

A localized infection of the hair follicles resulting in red bumps or pus-filled papilla.

Furuncle

Commonly called a boil, this is a painful, warm, pus-filled nodule at the site of a hair follicle.

Carbuncle

A massive sore or abscess formed when multiple furuncles combine; it is deep and can lead to systemic infections.

Impetigo

A highly contagious infection caused by staph or strep characterized by vesicles that rupture and form a yellowish crust.

Nonbullous impetigo

A form of impetigo characterized by vesicles and pustules that rupture and crust over.

Bullous impetigo

A severe form of impetigo with large fluid-filled blisters and draining lesions.

M protein

A virulence factor on the surface of Streptococcus that allows it to adhere to tissues and inhibit phagocytosis.

Lansfield groups

A classification of Streptococcus based on carbohydrates in the cell walls, labeled groups A through M.

Alpha hemolysis

An incomplete breakdown of red blood cells by Streptococcus, appearing as an olive green color on blood agar.

Beta hemolysis

The complete destruction of red blood cells by Streptococcus, appearing as clear areas on blood agar.

Erysipelas

A bacterial infection of the dermis caused by Group A strep, resulting in fiery red skin with sharp borders, edema, and pain.

Cellulitis

A deeper infection of the dermis and hypodermis characterized by redness, swelling, and lymphangitis.

Lymphangitis

Red lines indicating the spread of infection along a lymphatic vessel toward the heart, often associated with cellulitis.

Acute necrotizing fasciitis

A dangerous infection that spreads into the fascia and muscle, causing systemic shock with a mortality rate of $40\%$ to $60\%$.

Debridement

The surgical removal of dead tissue to allow a wound to heal from the inside out.

Gas gangrene

Also known as myonecrosis, a bacterial infection caused by Clostridium perfringens that produces gas and foul odors while destroying tissue.

Clostridium perfringens

An anaerobic, spore-forming organism that thrives in tissues with reduced circulation to cause gas gangrene.

Proteases

Powerful enzymes secreted by Clostridium perfringens that break down proteins and create a foul odor.

Propionibacterium acnes

A normal inhabitant of the skin that feeds on oil and causes localized inflammation known as acne.

Comedones

Wart-like lesions of acne including whiteheads (closed) and blackheads (oxidized lipids open to the air).

Cutaneous anthrax

Also known as Wolsorder's disease, caused by Bacillus anthracis, following exposure to animal products like wool.

Escher

A black necrotic sore that forms at the site where Bacillus anthracis spores enter the skin.

Human papillomavirus (HPV)

A DNA virus that causes benign epithelial growths commonly known as warts.

Oral herpes

An infection caused by Herpes Simplex Virus ($HSV-1$ or $HSV-2$) resulting in cold sores or fever blisters.

Trigeminal nerve

The cranial nerve where the oral herpes virus lays dormant in sensory neurons between outbreaks.

Fitt's disease

A viral illness caused by human parvovirus $B19$, characterized by a slapped face appearance and a maculopapular rash.

Erythema infectiosum

The slapped face rash characteristic of Fitt's disease.

Roseola

Also called sixth disease, caused by human herpes virus $6$ or $7$, characterized by a high fever followed by a maculopapular rash.

Molluscum contagiosum

A viral infection producing smooth, waxy nodules with a pearl-like appearance and a central depression.

Tinea

A group of fungal infections, originally called ringworm, caused by dermatophytes such as Trichophyton, Epidermophyton, and Microsporum.

Tinea corporis

A fungal ringworm infection found on the body.

Tinea capitis

A fungal ringworm infection found on the scalp.

Tinea pedis

A fungal ringworm infection found on the feet.

Tinea cruris

A fungal ringworm infection of the groin region, commonly known as jock itch.

Tinea unguium

A fungal infection of the nails.

Cutaneous candidiasis

An opportunistic yeast infection caused by Candida albicans that thrives in warm, moist environments like diaper areas.

Sporotrichosis

A fungal infection caused by Sporothrix shenchii, often introduced via rose thorn punctures and treated with oral antifungals for $3$ to $6$ months.

Conjunctiva

Mucous membranes covering the eyeball and lining the inner eyelids.

Bacterial conjunctivitis

Redness of the eye with a purulent discharge ($yellow$, $green$, or $white$) that can glue the eyelids shut.

Neonatal conjunctivitis

Conjunctivitis in newborns caused by Neisseria gonorrhoeae or Chlamydia trachomatis, treated with antibiotic drops at birth.

Viral conjunctivitis

Inflammation of the conjunctiva caused by viruses like adenovirus, resulting in a watery discharge.

Trachoma

Also known as granular conjunctivitis, caused by Chlamydia trachomatis; it can cause eyelashes to turn inward and lead to blindness over $10$ to $15$ years.

Onchocerciasis

Also known as river blindness, caused by the roundworm Onchocerca vulvulus and transmitted by black fly bites.

Ivermectin

An antihelminthic drug used to treat Onchocerciasis (river blindness).