skin 3: exotoxin-mediated, erysipelas and cellulitis Flashcards
Staphylococcal Exfoliatin-toxin mediated diseases include:
Bullous impetigo
Staphylococcal scalded skin syndrome (SSSS) including Ritter’s Disease of the newborn
Scarlet fever-LIKE syndrome
pathogenesis
Caused by exfoliatin toxin (ET) –producing strains of Staphylococcus aureus
ET causes an epidermal desquamation of superficial intraepidermal layers of
skin (cleavage in epidermis).
Produces Nikolsky sign and/or bullae; No inflammation or necrosis, no scarring unless 2o infection occurs
Nikolsky sign
Epidermal necrosis - sloughing of large layers of skin. Sloughing with oblique pressure
Bullae
flaccid, paper thin (thin-walled) white, serous fluid-filled sacks which rupture–>painful, moist, denuded erythematous lesions that dry in 1-2d to thin “varnish-like” light-brown crusted lesions
Bullous impetigo
Occurs in infants, young children on exposed areas of face, legs.
Bullae contains organism
Toxin(s) and organism remain localized
NO Nikolsky sign
Staphylococcal scalded skin syndrome (SSSS) complex
Occurrences primarily in:
infants-children 5 years or younger
immunocomprimied adults
SSSS pathogenesis
Usually a focal infection by ET-producing strains.
Dissemination of staphylococci is rare; Focal infection is contagious (toxin disseminates)
ET produced in the focal lesion spreads hematogenously resulting in skin lesions/bullae which are sterile
(diff than bullous impetigo: org in lesion)
SSSS manifestations
syndromes – SSSS and Ritter’s disease of the
newborn/neonate
SSSS
Fever
Lesions:
Widespread, diffuse erythroderma (scarlatiniform rash).
Progresses in 1-3d to extensive in size, widely distributed, spontaneous, exfoliation of skin and/or bullae that progress as described above. Positive Nikolsky sign
Erythematous, dry, fissuring, peeling, bleeding lips often occur.
Within 5 d of onset, a fine, flaky, discolored, total-body desquamation occurs.
Purulent conjunctivitis may occur.
most severe form of SSSS
Ritter’s disease of the newborn/neonate
Scarlet fever-Like Syndrome.
(coming later)
dx bullous impetigo, SSSS and Ritter’s
Pyodermic staphylococcal infections diagnosed by culture and Gram- stain, also assay for elevated levels of anti-teichoic acid antibodies by gel diffusion
or CIE.
px bullous impetigo, SSSS and Ritter’s
Usually rapid recovery with effective treatment
tx of bullous impetigo, SSSS and Ritter’s
Supportive, i.e., fluid replacement and pain management.
Antibiotics:
MRSA are common in community and nosocomial outbreaks. For impetigo involving limited body surface area, topical antibiotics such as mupirocin.
For patients with systemic symptoms, oral antibiotics should be considered. Topical antiseptics such as hydrogen peroxide should NOT be used in the treatment of impetigo.
Streptococcus pyogenes
G+, chain-forming cocci; Group A, β-hemolytic. (GABHS).
Classification of streptococci is based on 3 independent groupings:
Lancefield serotypes AT.
T protein serotypes based on groups A, B, C, G.
M protein types (>90 serotypes).
S. pyo virulence factors
M protein (>90 types; antiphagocytic).
Toxins: streptococcal pyrogenic exotoxins (SPEA, B, C; etc. aka erythrogenic
toxins).
S. pyo pathogenesis
Suppurative diseases (pus producing): Pharyngitis and related infections vs. Integumental and soft tissue infections.
S. pyo Pharyngitis and related infections, rheumatic fever (RF), AGN, scarlet fever (SF): M types?? spread?? seasonality?? age group??
- Lower numbered M types.
- Direct spread by droplet nuclei from person with pharyngitis or carrier
- Colder months of the year (winter and early spring).
- Highest incidence in 5-15 year old.
S. pyo integumental (impetigo, ecthyma) and soft tissue infections (AGN, SF) M types?? spread?? associated with?? seasonality?? age group??
-Higher numbered M types.
-Direct spread, agent colonizes skin surface, minor trauma or
insect bite allows for agent to cause infection. —Also associated with poor hygiene
-Warmer months of the year
-Highest incidence in children less than 6 y-o-age.
S. pyo Non-suppurative diseases/sequelae/autoimmune disease
Rheumatic fever (RF) may follow pharyngeal infection.
Post-streptococcal Reactive Arthritis (PRSA).
Pediatric Autoimmune Neuropsychiatric Disorders Associated with
Streptococcal Infections (PANDAS).
Acute glomerulonephritis (AGN) may follow pharyngeal or
integumental infections
Exotoxin-mediated diseases (superantigens):
Streptococcal toxic shock syndrome (STSS): SEE TSS
Scarlet fever