Infection: Staphlococcal And Group A Streptococcal Infections Flashcards
Staph and strep infections are usually caused by…
Direct invasion of the organisms
They can also cause disease by releasing toxins, which act as superantigens
What are superantigens?
Conventional antigens stimulate a small subset of T cells, which have specific antigen receptor, superantigens bind to a part of the T cell receptor that is shared by many T cells - stimulates a massive T cell proliferation and cytokines release
What diseases can follow streptococcal infections?
Poststreptococcal glomerulonephritis
Rheumatic fever
Describe impetigo
A localised, highly contagious staphylococcal or streptococcal skin infection
What bacterial typically causes impetigo?
Staphylococcus aureus
Streptococcal pyogenes
Impetigo most commonly occurs in what age group?
Infants and young children - especially if pre existing skin disease e.g eczema, scabies, insect bites
Where do impetigo lesions typically occur?
Face, neck, hands, flexures and areas not covered by clothes
Describe the lesions that occur with impetigo
Begin as erythematous macules that can become vesicular and pustular or even bullous.
Rupture of lesions leads to the characteristic honey coloured crusted lesions
How is impetigo spread?
Direct contact with discharges from the scabs of an infected person
The bacteria invade skin through minor abrasions and then spread to other sites by scratching
Infection is spread mainly by the hands, but indirect spread via toys, clothing, equipment and the environment may occur
How is limited, local, impetigo managed?
Hydrogen peroxide 1% cream 2-3 times a day for 5 days
If unsuitable - short course of topical antibiotics:
Fusidic acid 2% TDS for 5 days or Mupirocin 2%
How is widespread, but non-bullous impetigo managed?
Short course of topical or oral antibiotic (flucloxacillin or clarythromycin for 5 days)
How should bullous impetigo or impetigo in those systemically unwell, be managed?
Short course of oral antibiotics - flucloxacillin for 5 days
Should children with impetigo go to school?
No, not until lesions crusted or antibiotics for 48 hours
What are boils?
Infections of hair follicles or sweat glands, usually cause by staphylococcus aureus
How are boils treated?
Systemic antibiotics and occasionally surgical incision
What are recurrent boils usually due to?
Persistent nasal carriage in child or family acting as a reservoir for reinfection.
Only rarely are they a manifestation of underlying immunodeficiency
What is periorbital cellulitis?
Erythema, tenderness and oedema of the eyelid or other skin adjacent to the eye
Does not pass the orbital septum - thin sheet of fibrous tissue separating intra orbital contents from pre septal area
What is another term for periorbital cellulitis?
Pre septal cellulitis
Is periorbital cellulitis almost always unilateral?
Yes
How does periorbital cellulitis occur?
May follow from local trauma to skin
Spread from paranasal sinus infection or dental abscess
How should periorbital cellulitis be managed?
Promptly with IV antibiotics - high dose ceftriaxone
Why does periorbital cellulitis require prompt treatment?
Prevent posterior spread of infection, causing orbital cellulitis
What features differentiate orbital from periorbital cellulitis?
Proptosis
Painful ocular movement
Limited ocular movement
With/without reduced visual acuity
When orbital cellulitis is suspected, what imaging should be done?
CT or MRI to assess for posterior infection spread
What complications can occur with orbital cellulitis?
Abscess formation
Meningitis
Cavernous sinus thrombosis
What is staphylococcal scaled skin syndrome?
When an exfoliative staphylococcal toxin causes separation of the epidermal skin through the granular cell layers
What features are associated with staphylococcal scalded skin syndrome?
Fever
Malaise
Purulent, crusting and localised infection around eyes, nose, mouth
Subsequent widespread erythema and tenderness of skin
Areas of epidermis separate on gentle pressure (Nikolsky sign)
How is staphylococcal scalded skin syndrome treated?
IV anti- staphylococcal antibiotics e.g flucloxacillin
Analgaesia
Monitoring of hydration and fluid balance
