Flashcards in Week 3 - Case 1 Follow up Deck (18):
What does the exotoxin for SSSS do?
It destroys keratinocyte attachments in the stratum granulosum only (vs. toxic epidermal necrolysis, which destroys the epidermal-dermal junction)
What is SSSS characterized by?
It is characterized by fever, generalized erythematous rash with sloughing of the upper layers of the epidermis that heals completely. Seen in newborns and children.
Where should you look for Staphylococcus for culturing? (SSSS)
>90% positive cultures are found for SSSS in the nasopharynx
<10% in the skin and blood
What is the significance of ET-A and ET-B?
They are exofoliative toxins released by Staphylococcus aureus. They both target desmoglein-1 for destruction (this is the intercellular protein that binds cells together in desmosomes)
-Destruction of desmoglein-1 breaks apart a key protein to protein interaction that serves to hold together desmosome cells.
What is unique about ET-A?
It encoded by lysogenized phage and is implicated in bulbous impetigo.
What is unique about ET-B?
It's encoded by a plasmid which is found in about 5% of all strains of S. aureus - is implicated in SSSS. SSSS most commonly affects neonates (Ritter's disease - infected umbilical cords) and young children.
What is Ritter's disease?
It is an infected umbilical cord caused by ET-B from Staphylococcal Scalded Skin Syndrome.
What is TEN (toxic epidermal necrolysis)?
Lyell's syndrome. Caused by a drug reaction. Epidermis deteches from the dermis. Secondary bacterial infections can be fatal. Mortality ~25%
What patients do SSSS and TEN affect?
SSSS- infants, young children, immunocompromised adults
What is the patient history for SSSS and TEN?
SSSS-Recent staphylococcal infection
TEN- drug use, renal failure
What is the level of epidermal damage for SSSS and TEN?
SSSS - within the granular cell (outermost) layer of the epidermis
TEN- between the epidermis and dermis or at the level of the basal cell
How do you differentiate SSSS and pemphigus?
Pemphigus punch biopsy can reveal autoantibodies (direct immunofluorescence) to desmoglein. Typically pemphigus occurs in older patients.
Pemphigus - autoantibodies to desmoglein, usually don't get a fever
SSSS- ET-B that targets desmoglein
How does Strep deal with peroxide (radicals) in comparison to Straph.?
Strep is catalase neg. and produces water (no bubbling)
Staph is catalase pos. and produces bubbling (O2 bubble escaping)
What needs to be present to cause skin condition of SSSS?
Just the toxin - do not need the bacteria
What are the 6 common childhood diseases?
2. Scarlet Fever (Strep. pyogenes)
3. Rubella (German measles)
4. Staphylococcus aureus (TSS/SSSS)
5. Parvovirus B19 (slapped cheek)
6. Roseola Viruses (HHV-6/7)
What does a bad sore throat and rash usually mean? What are two common pathogens associated with this?
EBV (Epstein Barr Virus)
What is S. pyogenes?
Causative agent of scarlet fever, has a higher rate of infection in children ages 5-15