Skin and Soft tissue Infections Flashcards
What bacteria colonise the skin as normal flora?
Coagulase-negative staphylococci,
Staph. aureus,
Propionibacterium,
Corynebacterium spp.
Where does Herpes simplex reside in its dormant state and how does a secondary infection present?
Dorsal root ganglions as episomes
When activated it migrates along the sensory nerves to form weeping, vesicular lesions
Which virus is usually responsible for cold sores and genital herpes?
Herpes simplex virus (HSV)
Peri-oral = HSV 1 Genital = HSV 2
What is the treatment for HSV?
Cold sores: Topical acyclovir
Genital herpes or immunosuppressed patient: Oral acyclovir
What causes shingles and what is seen on examination?
Varicella Zoster Virus (VZV) can reactivate to cause Herpes zoster (Shingles)
Weeping, vesicular rash
Dermatomal distribution
What is the treatment for herpes zoster?
Oral acicolvir / valaciclovir
IV aciclovir - depending on age of patient, immune status and severity of shingles
How does Molluscum contagiosum present clinically?
Raised, pearly lesions up to 3 mm
Umbilicated
No treatment needed - disappear after 6-18 months
What exotoxins does S. aureus produce?
Epidermolytic toxins A & B (ETA & ETB),
Toxic shock syndrome toxin (TSST-1),
Panton-Valentine leukocidin (PVL)
What is impetigo and its causative organisms?
Infection of epidermis (superficial)
Staph. aureus,
Strep. pyogenes
or both
What does impetigo look like upon examination?
Plaque-like lesions
Yellowish exudate
Thick scabs - “Honey crusted lesions”
What local and generalised complications of impetigo are caused by Epidermolytic toxin production (ETA & ETB)?
Localised: Bullous impetigo
Generalised: Staphylococcal scalded skin syndrome (SSSS)
Desmosomal glycoprotein desmoglein-1
Required for cell-to-cell adhesion in the superficial epidermis
Inactivated by ETA & ETB
What is Erysipelas its suspected causative agent?
Infection of dermis
Predominantly face or shin
Strep. pyogenes
What is Cellulitis and its usual causative agent?
Infection of skin and subcutaneous tissues
Staph. aureus
Strep. pyogenes
Pasteurella multocida (animal bites)
Haemophilus influenzae
Describe the bacteria that causes Anthrax
Bacillus anthracis
Spore-forming aerobic Gram-positive bacillus
How is Bacillus anthracis acquired and how does it present?
Acquired from imported wool, hair and animal hides
Inoculation through breaks in the skin:
a painless ulcer with a black centre (eschar)
What causes Type 1 Necrotising fasciitis?
Type 1: Polymicrobial
- Enteric Gram-negative bacilli
- Anaerobes
What causes Type 2 Necrotising fasciitis?
Type 2: Streptococcus pyogenes
How does necrotising fasciitis present and how is it treated?
Spontaneous or at site of skin penetration, Any part of body
Fever & malaise + Dark, rapidly spreading, necrotic lesion
Treatment: Intravenous antibiotics and Surgical debridement
Where do you most commonly find anaerobic infections of the skin?
Gas gangrene
Usually post-operative surgical sites
eg. amputations
What organism causes anaerobic infections of the skin?
Clostridium perfringens (anaerobic Gram-positive bacillus)
Causes gas gangrene
What is the empiric treatment for Staph. aureus or Strep. pyogenes infections
Flucloxacillin
What is the empiric treatment for impetigo?
Fusidic acid or mupirocin
What is the empiric treatment for Necrotising fasciitis?
need to cover anaerobes, Enterobacteriaceae, streptococci and staphylococci
Meropenem + clindamycin
What is the most like suspect for gas gangrene and how is it treated?
Clostridium perfringens
Intravenous antibiotics
Surgical debridement
