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