Layers of skin (3) Epidermis Dermis Subcutaneous ◦ Gives rise to hair follicles and sebaceous glands (oil and sweat)

Layers of skin (3)

Epidermis Dermis Subcutaneous

◦ Gives rise to hair follicles and sebaceous glands (oil and sweat)

Protection from environmental factors

Barrier to infection Sensitive to pressure

◦ Pacinian corpuscles Nerve endings for light

touch/light sensation – hairs standing on end when excited/nervous

Break or breach of the skin

Associated with systematic infection

Toxin mediated by

microorganism that is actually infecting some other site of body and producing toxins that effect the skin

Break or breach of the skin

◦ Enter the body through carbuncles etc... usually associated with puss

Associated with systematic infection – see symptoms on the skin

◦ Chicken pox◦ Herpes◦ Syphilis◦ Small pox

Toxin mediated by microorganism that is actually infecting some other site of body and producing toxins that effect the skin

◦ Scarlet fever Streptococcus pyogenes is

causative agent◦ Scalded skin syndrome –

like third degree burns Staphylococcus aureus is

causative agent

Normal flora on our skin- we want to havethese microorganisms because they outcompete most other invading microorganisms for space and nutrients.

◦ Staphylococci◦ Yeast◦ Gram negative enterics◦ Diptheroids

Variety and amount of microorganisms on our skin is affected by

◦ temperature◦ moisture◦ pH◦ amount of sweat

produced◦ chemicals excreted

Oleic acid Urea Sebum

Most common causes of skin infections are

Staphylococcus aureus and Streptococcus pyogenes .

Clinically Presented as:◦ Carbuncles◦ Boils◦ Pimples◦ Furnucles

Most common skin infection in children.

Signs and symptoms: local infections, characterized by isolated pustules that become crusted and rupture

Transmission: mostly through contact, bacteria penetrate skin through minor abrasion or insect bite

Causative agent: S. pyogenes

Tx: Topical antibiotic-Bactroban, Systemic antibiotics-Cephalexin, Erythromycin

Infection of hair follicle

Signs and symptoms: rash, pimples surrounding hair follicle, itching, reddened skin area

Transmission: result of injury or damage to hair follicle

Causative agent: S. aureus

Tx: Topical antibiotic-Bactroban, Systemic-Erythomycin

Severe type of tissue infection that can involve the skin, subcutaneous fat, the muscle sheath (fascia), and the muscle. It causes gangrenous changes, tissue

death, systemic disease, and frequently death.

Signs and Symptoms: Severe pain in the area swelling in the area Discoloration in the area May appear reddened, bronzed,

bruised, or purple (purpuric) Progresses to dusky, dark color Bleeding into the skin Visible dead (necrotic) tissue Skin color, patchy Skin breaks (open wound) Skin around the wound feels hot and

looks reddened, raised, or discolored (inflammed)

Oozing fluid ranging from yellowish clear or yellowish bloody to pus-like

fever General ill feeling (malaise)

Causative Agent: Streptococcus pyogenes Mycobacterium ulcerans Vibrio vulnificus)

Tx: Powerful broad-spectrum antibiotics must be administered immediately. They are given intravenously (in a vein) to attain high blood levels of the antibiotic in an attempt to control the infection. Surgery is required to open and drain infected areas and remove (debride) dead tissue.

Skin grafts may be required after the infection is cleared. If the infection is in a limb and cannot

be contained or controlled, amputation of the limb may be considered. Sometimes pooled immunoglobulins (antibodies) are given by vein

to help fight the infection.

Fatalities are high

A type of (cellulitis) skin infection

◦ Signs and Symptoms: An erysipelas skin lesion

typically has a raised border that is sharply demarcated from normal skin. The underlying skin is painful, intensely red, hardened (indurated), swollen, and warm.

Facial erysipelas classically involve the cheeks and the bridge of the nose.

Blisters may develop over the skin lesion.

Fever and shaking chills are common

◦ Causative Agent: S. pyogenes

Etiology Bacillus anthrax

Gram-positive

Endospore forming

3 clinical manifestations◦ Cutaneous◦ Pulmonary◦ GI

Flu like symptoms

Malignant pustule called eschar – surrounded by swelling (edema) rednessblack in the middle becomes a scab.

Not common – associated with an occupation or hobby that involves livestock or ranching

◦ Spores can be inhaled in the lungs◦ Very pathogenic◦ Known as Wool Sorters disease –

associated with livestock◦ Organism is beta hemolytic with a

double zone of hemolysis◦ Organism has a polyglutamic acid

capsule ◦ Organism produces at least three

toxins Destroy tissues and cells Promotes growth of organism in

tissues If it becomes systemic it can spread

through lymph◦ Vaccination available but it is

usually not give to humans (just animals)

◦ PCN is drug of choice

Etiology Mycobacterium leprae Causative agent related to TB Development of multiple lesions on

skin Loss of sensory perception in areas

of skin that have been infected◦ Areas that are cooler than body

temperature◦ Fingers◦ Toes◦ Nose◦ Elbows◦ Ears

Organism doesn’t actually damage but the body’s cell mediated response destroys the nerve endings (pacinian corpuscles)

Organism is acid fast

The average generation period is about 12-14 days. 1 cell becomes 2 during this period. Pretty slow growing bug.

Incubation period is 12 weeks to 40 years! With a mean of two years

BCG – vaccine for TB, preventative for leprosy

Not very common Tx - topical steroids can be

used to control swelling. Dapsone used for treatment. 

Severe disease caused by a toxin made by S. aureus or S. pyogenes, characterized by shock and multiple organ dysfunction.

◦ Signs and Symptoms: High fever, sometimes

accompanied by chills Profound malaise Nausea, vomiting and/or diarrhea Diffuse red rash resembling a

sunburn Rash followed in 1 or 2 weeks by

peeling of the skin, particularly the skin of the palms or soles

Redness of eyes, mouth, throat Confusion, seizures, headaches Myalgias (muscle aches) Hypotension (low blood pressure) Organ failure (usually kidneys and

liver)

Causative agent: S. pyogenes

Childhood disease famous in 1800s

Begins as pharyngitis, organism begins to produce toxin

  Symptoms:

◦ Pinkinsh-red rash covers the whole body except palms of hands and soles of feet

◦ Rash is the body’s rxn to the circulating toxin

◦ Tongue has spotted, strawberry appearance and the upper membrane is lost. Red and large

Bacterial conjunctivitis due to the common pyogenic (pus-producing) bacteria causes marked grittiness/irritation and a stringy, opaque, grey or yellowish mucopurulent discharge (gowl,

goop, "gunk", "eye crust") that may cause the lids to stick together (matting), especially after sleeping.

Common etiologies: S. aureus and C. trachomatis

Bacterial Neonatal Gonorrheal Opthalmia: serious form of conjunctivitis

Symptoms: Acute infection with much pus formation At more advanced stages

ulcers form on cornea infection carries high risk of

blindness Causative Agent:

Neisseria gonorrhoeae Transmission: acquired as

infant passes through the birth canal

Rx: oral Tetracycline or Erythromycin drops for prevention

Keratitis is a condition in which the eye's cornea, the front part of the eye, becomes inflamed. The condition is often marked by moderate to intense pain and usually involves impaired eyesight.

Herpetic Keratitis: Herpes simplex keratitis is a serious viral infection. It may have recurrences that are triggered by stress, exposure to sunlight, or any condition, disease or treatment which impairs the immune system.

◦ Symptoms: eye pain Impaired vision Eye redness White patch on the cornea Sensitivity to light Increased tearing

Causative Agent: Herpes simplex 1 (cold

sores)Transmission: problem for contact lens wearers especially

Frequently results in severe eye damage

Symptoms: eye pain Impaired vision Eye redness White patch on the cornea Sensitivity to light Increased tearing

Transmission: contact lenses

Tx: Topical ointment (propamidine or miconazole), corneal transplant or eye removal may be required