Ch.19 L.3

Staphylococcal Scalded Skin Syndrome

Impetigo (Pyoderma and Erysipelas)

Pathogen and virulence factors

Diagnosis

Epidemiology

Treatment

Pathogenesis

Prevention

5% of strains of Staphylococcus aureus secrete one or two distinct exfoliative toxins which cause SSSS

No scarring because the epidermis is unaffected by the toxin. The body restores the lost epidermis within 7-10 days.

Primarily a disease of infants and children under the age of 5.

made by the distinctive sloughing of the skin

IV drugs like semisynthetic nafcillin or oxacillin that do not let β-lactamase to bind (remember that β-lactamase deactivates many drugs in the PCN class)

Little can be done to prevent SSSS because S. aureus is normally on the skin

What is it?

What happens is cells of the outer epidermis separate from one another and from the underlying tissues.

Signs and Symptoms

Reddening and wrinkling of the skin usually near the mouth, spreads over entire body

Large blisters that have clear fluid (no bacteria)

Within 2 days skin peels off in sheets (flesh having been dipped into boiling water)

Both of these toxins affect keratinized cells of the epidermis

The blood carries these toxins from the site of infection throughout the body. This circulation of toxins in blood is called toxemia

Mortality (death) is rare but if one does die, it is from a secondary infection of skinless areas by yeast like Candida albicans or by a bacteria like Pseudomonas aeruginosa

It can affect the elderly, immunosuppressed patients, like those with AIDS

Transmission is by person to person spread of the bacterium onto skin surfaces and then the pathogen will penetrate cuts and abrasions.

Epidemiology

Diagnosis

Pathogenesis

Treatment

Pathogen and virulence factors

Prevention

Signs and Symptoms

Vesicles are oozing, puss filled on a red base. They eventually break and form a thick sticky crust that is attached to the skin and cause intense itching

Small, flattened, red patches appear on the face and limbs

End up with numerous vesicles at different stages of development because bacteria will spread to other areas

erysipelas

When the infection spread into surrounding lymph nodes and triggers pain and inflammation the condition is called

Most cases are caused by S. aureus in 80% of cases

20% of cases involve S. pyogenes alone or with S. aureus (both together is group A Strep.

Virulence factors add to impetigo

Hyaluronic acid

Pyrogenic toxins proteins

M protein

cytoplasmic membrane that destabilizes complement and interferes with phagocytosis

serves as a camouflage for the bacteria, hiding it from phagocytosis

stimulate macrophages and helper T-lymphocytes to release cytokines that will in turn stimulate fever, widespread rash, and shock

Some strains of S. pyogenes may spread from impetigo or erysipelas into the blood (bacteremia) and then to the kidneys, where acute glomerulonephritis can result

Bacteria occasionally colonize the skin and then invade through scratches , abrasions, cold sores or other wounds

Children are often infected just below the nose(frequent wiping will abrade the skin

Both Staph & Strep spread by person to person contact or via fomites (toys, clothing, bedding, towels, or hairbrushes)

Epidemics of impetigo in nurseries are of concern

Erysipelas occurs most commonly in children and elderly

Children ages 2-5 are most likely to get/develop impetigo

Vesicles of impetigo

oral and topical antimicrobials(mupirocin, oral clindamycin, doxycycline)and careful cleaning of infected areas

proper hygiene and cleanliness