Human Skin

Perspiration and Sebum contain nutrients
Salt INHIBITS microbes
Lysozyme hydrolyzes peptidoglycan (in sweat)
Fatty acids INHIBIT some pathogens
Antimicrobial peptides - defensins

Mucous Membranes

Line Body cavities
Cells secrete mucus
muc mem. often acidic
Some cells have cilia
In eyes, washed by tears with lysozyme

Normal Microbiota of the skin

GRAM-POSITIVE SALT TOLERANT BACTERIA
Staphylococci, micrococci, an diphtheroids

More Norm microbiota of skin

Grow on oils
Aerobes are on the surface
Anaerobes are in the hair follicles
USUALLY DISPLAY SYMBIOTIC, COMMENSAL RELATIONSHIP

Microbial diseases of the skin

Exanthem, Enanthem

Exanthem

skin rash arising from another focus of the infection

Enanthem

mucous membrane rash arising from another focus of the infection

Staphylococcus epidermidis

gram-positive cocci, coagulase negative (staph skin infection)

Staphylococcus aureus

Gram- positive cocci, coagulase positive (Staph skin infection)

S. AUREUS

Antibiotic resistant, leukocidin (compound that destroys neutrophils
and macrophages), resists opsonization, survives phagolysosome,
lysozyme resistant, superantigen, golden yellow color protects it from sunlight

Folliculitis

infections of the hair follicles

Sty

Folliculitis of an eyelash

Furuncle

Abscess pus surrounded by inflamed tissue

Carbuncle

inflammation of tissue under the skin

impetigo

crusting (nonbullous) sores spread by autoinoculation

Scalded Skin Syndrome

Bullous impetigo
Impetigo of the newborn

Streptococcal Skin Infections

Streptococcus pyogenes (flesh eating bacteria)

M Proteins

prevent activation of complement and avoid phagocytes

Infections by Pseudomonads

Pseudomonas aeruginosa, gram-negative rod
Pyocyanin produces blue-green pus
Pseudomonas dermatitis
Otitis externa - swimmers ear
Post-burn infections
Opportunistic

Buruli Ulcer

Caused by mycobacterium ulcerans
deep, damaging ulcers
exceeds incidence of leprosy

Classifications of Acne

Comedonal (mild)
Inflammatory (moderate)
Nodular cystic (Severe)

Comedonal Acne

Mild
Sebum channels are blocked with shed cells
Treatment:
Topical agents, salicylic acid preparations, Retinoids, Adapalene (aspirin)

Inflammatory Acne

Propionibacterium acnes - gram-positive, anaerobic rod
Treatment:
Preventing sebum formation (isotretinoin)
antibiotics
benzoyl peroxide to loosen clogged follicles
visible (blue) light kills P. acnes

Nodular cystic (severe) acne

Severe
Treatment:
Isotretinoin (accutane)
teratogenic, harmful to fetus

Warts

Papillomaviruses
Treatment
Removal

Poxviruses

Smallpox (variola)
Smallpox virus (orthopoxvirus)
variola major 20% mortality
variola minor less than 1%
eradicated by vaccination
Monkeypox
prevented through small pox vaccination

Cutaneous Mycoses

Dermatomycoses
Also known as tineas or ringworm -metabolize keratin

Candidiasis

Candida albican (yeast)
result of antibiotics suppressing competing bacteria
occurs in skin and mucous membranes of genitourinary tract and mouth
Thrush: an infection of mucous membranes of mouth

Scabies

Sarcoptes Scabiei - burrows in the skin to lay eggs
treatment of topical insecticides

Pediculosis

(LICE)
Pediculus humanus capitis (head louse)
P.h. Corporis (body louse)
-feed on blood
-lay eggs (nits) on hair
topical insecticides

Conjunctivitis

An inflammation of the conjunctive
Also called pinkeye or red eye
commonly caused by Haemophilus influenzae
other microbes can cause it too
associated with unsanitary contact lenses

Vesicle

small, fluid filled lesions

Bullae

vesicles larger than 1 cm in diameter

macules

red, flattened lesions

papules

raised lesions

pustules

raised lesions with pus (dead phagocytes, bacteria, etc)