Lecture 22 Skin Infections Flashcards
Epidermis
Has dead cells that are filled with keratin. Keratin kills the cell and is a water resistant protein found on hair and nails. The skin flakes off removing the microorganisms living on the epidermis layer.
The outermost layers are bathed in secretions
Dermis
Provides the epidermis with nutrients and removes wastes from it. Has blood cells and glands and nerves.
The glands produce sweat and sebum (oily secretion). The sweat evaporates and leaves a salty residue that inhibits bacteria.
The sebaceous glands open into hair follicles so that sebum flows up through the follicles and over the skin surface. It keeps the hair and skin soft pliable and water repellent
Subcutaneous tissue
Supportive tissue containing fat and other types of cells
Normal microbiota on skin
Since the skin is cold and dry, it recruits Normal microbiota because Normal microbiota thrive in this env. And use sebum and nutrients and produce toxin to prevent other microbes from living on skin.
Most pathogens don’t survive because the skin is too dry salty acidic and toxic for their survival. And those that tolerate are usually shed by the dead skin.
Some are opportunistic pathogens, causing disease in people with impaired body defenses.
What is responsible for body odor?
Bacteria metabolizing sweat.
What areas of the body have the most bacteria?
Armpit and groin. Has the most moisture.
Categorization of the members of the normal microbiota of the skin
Diphtheroids: variably shaped, non motile, gram positive rods of the corynebacterium and propionibacterium genus
Common in oily regions (forehead chest back)
Staphylococci: gram positive cocci arranged in packets or clusters; facultative anaerobe
Grow on dry surfaces
Fungi: small yeasts of the genus malassezia that require oily substances(needs the lipids) for growth
How can anaerobic bacteria like propionibacterium grow on human skin?
They grow within hair follicles where the O2 is limited.
Acne vulgaris
Caused by propionibacterium acnes. Use sebum to grow and multiply. The metabolic process of the dividing bacteria causes an inflammatory response that attract neutrophils and causes the Follicle to burst and an abscess is formed (a collection of pus surrounded by inflamed tissue). The pus has the dead neutrophils and bacteria.
Hormones stimulate sebum production which causes acne.
Blackhead = plug
Whitehead = bulge
Functions of skin
Prevents entry of microbes, regulates body temperature, restricts the loss of fluid from body tissues, has sensory receptors, helps with immune system (if skin is broken, it signals the cytokines to be released and immune system to start)
Hair follicle infections
Folliculitis - inflammation
Furnicle - boil (localized swelling)
Carbuncle - large area of redness, draining pus
Caused by S. aureus - because it clumps/coagulates the plasma (hides it from the immune system)
Transferred from one host to another via fomites
Exfoliatin
destroys material that binds outer layers of the epidermis together, causes scalded skin syndrome
disease occurs in infants
malaise - discomfort
blisters, sandpaper
secondary bloodstream infection and loss of body fluids lead to death
Protein A
binds to Fc portion of antibody, interfering with opsonization, prevents phagocytosis
Toxic shock syndrome
enterotoxins are ingested and cause rash, diarrhea, and shock
A toxin
makes holes in the host membrane
