Bacterial Skin Infections Flashcards
Most common causes of skin infections in immunocompromised people?
Staphylococci and streptococci
Infections begin with break in skin barrier
May see unusual or more severe infections
Medications that work for most bacterial skin infections?
first generation cephalosporins, pecillinase-resistant penicillins (MRSA becoming an increasing problem)
What organisms make up the normal skin flora?
Function to prevent skin infections:
- staph epidermidis
- corynebacterium spp –> intertriginous areas
- propionibacterium spp: sebaceous glands (acne)
- gram negative bacteria in axillae and groin
- yeasts (pityrosporum spp) on skin rich in sebaceous glands like central chest and upper back
Characteristics of Impetigo
- most common cutaneous infection in children
- causative pathogens: s. aureus, Group A strep (beta hemolytic) or both
- staph more predominant now
two clinical variants –> nonbullous (crusted) and bullous
Epidemiology of impetigo
usually affects young children
occurs year round
heat, humidity, crowding and poor hygiene predispose
spread by direct contact, autoinoculation
nasal colonization may serve as a source of infection for s. aureus
Common presentation of impetigo
often located around nose and mouth
- moist, honey colored crusts on erythematous base
- fever, systemic symptoms are rare
- may itch
- may be preceded by skin trauma
- often complicates atopic dermatitis to cause secondary impetiginization
Presentation of Bullous impetigo
May arise without obvious trauma
- large, flaccid bullae may develop
- blisters rupture leaving shiny, shallow erosions
- adenopathy, systemic symptoms are rare
- cleavage result of epidermo;ytic toxin produced by staph (exfoliatin)
Treatment of Bullous impetigo
- antibiotic coverage should cover for both staph and strep.
- for mild cases: mupurocin cream
- widespread/complicated cases: penicillinase-resistant penicillins or first generation cephalosporins
- culture/sensitivities recommended due to rise of resistant organisms
Recurrent cases: treat nares with mupurocin, body with chlorhexidine (hibiclens) or bleach baths soaking for 15min
Complications of impetigo
- may progress to ecthyma (deeper infection)
- staph scalded skin syndrome
- glomerulonephritis (not rheumatic fever) can complicate strep A impetigo.
Antibiotic tx doesnt prevent nephritis
Appearance of staphylococcus scalded skin syndrome
Skin just peals off leaving a smooth base
Characteristics of staphylococcus scalded skin syndrome
- diseases resulting from toxin produced by bacteria
- most common causes are s. aureus, phage group 1 strains
They produce exotoxins like exfoliatin (ETA and B) that circulate systemically, split the skin at superficial granular layer
Epidemiology of staph scalded skin syndrome
affects children less than 6, rarely immunosuppressed adults, especially with renal failure
typical clinical picture of staph scalded skin syndrome
- site of infection may or may not be apparent
- prodrome of malaise, fever, irritability
- skin becomes tender then develops symmetrical sundron-like erythema around facial orficies, neck and flexures
- skin superficially blisters, then sloughs leaving behind moist skin, scales
- heals without scarring 10-14days
Diagnosis of staphylococcus scalded skin syndrome
diagnosis is primarily clinical
- cultures from affected skin, blisters negative
- may culture staph from nare, conjunctiva, small foci of infection (pustules)
What is the prognosis for scalded skin syndrome?
- good in healthy children (3% mortality)
- bad in adults (over 50% all adults, up to 100% in adults with underlying disease)
- Must be distinguished from toxic epidermal necrolysis
