Ch 21 (in progress)

Epidermis

Outer layer of skin

Stratum corneum

Outermost layer of the epidermis

Keratin

Protective protein found in the epidermis

Dermis

Middle skin layer containing follicles, glands, and connective tissue

Hair follicle

Structure in the dermis that produces hair

Sebaceous gland

Gland that produces sebum

Sweat gland

Gland that produces sweat for thermoregulation

Hypodermis

Deepest skin layer composed of fat and connective tissue

Normal skin microbiota

Wide variety of microbes; some harmless, some opportunistic; inhibits transient colonization

Abscess

Localized collection of pus

Bulla

Fluid-filled blister larger than 5 mm

Carbuncle

Deep, pus-filled abscess formed from multiple furuncles

Crust

Dried fluids from a lesion on the skin surface

Cyst

Encapsulated sac filled with fluid, semi-solid matter, or gas

Folliculitis

Localized rash due to inflammation of hair follicles

Furuncle

Pus-filled abscess due to infection of a hair follicle

Macules

Smooth, flat spots of discoloration

Papules

Small raised bumps on the skin

Pseudocyst

Lesion resembling a cyst but with a less defined boundary

Purulent

Pus-producing; suppurative

Pustules

Fluid- or pus-filled bumps on the skin

Pyoderma

Any pus-producing infection of the skin

Suppurative

Producing pus; purulent

Ulcer

Break in the skin; open sore

Vesicle

Small fluid-filled lesion

Wheal

Swollen, inflamed, itchy or burning area of skin

Maculopapular rash

Rash with both flat (macules) and raised (papules) lesions; seen in measles, chickenpox, rubella

Cornea

Transparent front part of the eye that refracts light

Conjunctiva

Thin membrane covering the sclera and inner eyelids

Lacrimal glands

Produce tears

Lacrimal sac

Collects tears from the canaliculi

Lacrimal ducts

Channels that drain tears

Lacrimal puncta

Small openings that drain tears into canaliculi

Nasolacrimal duct

Drains tears into the nasal cavity

Normal conjunctival microbiota

Normal microbes present on the conjunctiva

Conjunctivitis (pink eye)

Inflammation of the conjunctiva; may be acute or chronic

Blepharitis

Inflammation of the eyelids

Keratitis

Inflammation of the cornea

Keratoconjunctivitis

Inflammation of both the cornea and conjunctiva

Staphylococcus epidermidis

Common skin flora; opportunistic pathogen associated with medical devices

Staphylococcus hominis

Normal skin flora species

Staphylococcus aureus

Common skin flora; produces many virulence factors; often purulent

Confirmation of Staphylococcus

Gram-positive grape-like clusters; catalase positive; coagulase test; mannitol salt agar; staphylolysins

Staphylolysins

Hemolysins produced by Staphylococcus species

Coagulase test

Differentiates S. aureus (positive) from S. epidermidis (negative)

Mannitol Salt Agar

Selective/differential agar; S. aureus ferments mannitol (yellow), S. epidermidis does not (white/pink)

Staphylococcus aureus virulence factors

Exoenzymes (catalase, coagulase, hyaluronidase, kinase) and toxins (TSST, staphylolysins, erythrogenic toxins, exfoliatin A and B)

MRSA

Methicillin-resistant Staphylococcus aureus; can be community-acquired or healthcare-acquired

VRSA

Vancomycin-resistant Staphylococcus aureus; highly drug-resistant strain

Desquamation

Skin shedding; peeling of the outer layers

Staphylococcal scalded skin syndrome

S. aureus toxins cause erythema and desquamation; treated with IV antibiotics and fluid therapy

Impetigo

Skin infection caused by S. aureus or S. pyogenes; may involve co-infections

Nonbullous impetigo

Vesicles and pustules rupture and form encrusted sores

Bullous impetigo

Bullae form, fill with fluid, and rupture; larger lesions

Impetigo treatment

Topical or oral antibiotics

Nosocomial Staphylococcus epidermidis infections

Opportunistic; associated with catheters, prostheses, and indwelling devices; difficult to treat once past skin barrier

Streptococci

Gram-positive chains of bacteria

Lancefield groups

Classification system for Streptococci (Groups A-H)

Streptococcus pyogenes

Group A Streptococcus; produces extracellular enzymes, capsule, and M protein

M protein

Major virulence factor of S. pyogenes; anti-phagocytic

Streptococcal capsule

Helps evade immune detection

Cellulitis

Infection of dermis or hypodermis; caused by S. pyogenes or Staphylococci

Erysipelas

Large, intensely inflamed, suppurative patch of skin; caused by S. pyogenes

Erythema nodosum

Inflammation of subcutaneous fat cells

Necrotizing fasciitis

Severe infection also known as "flesh-eating bacterial syndrome"; toxins target fascia; rapid spread and tissue death

Necrotizing fasciitis treatment

Debridement, IV antibiotics, surgical intervention