bacterial skin infections

• chemical attributes of skin inhibiting growth of microbes

  low pH, low moisture content, sebaceous fluid, lysosomes
• gram negative organisms are usually unable to colonise the dry environment of the skin
• bacteria can penetrate the skin by:

  abrasions, existing diseases of skin, burns, surgical wounds, bites, instrumentation
• endogenous bacteria sources

  flora colonising the skin
• exogenous bacteria sources

  environment (dirt, water, hospital equipment)
• staphylococci appearance

  gram positive, pairs or short chains, grape like clusters
• staphylococci

  catalase positive, non-motile, facultative anaerobic, able to grow in high salt concentrations, cultured on HBA
• osteomyelitis

  caused by S. aureus, infection and inflammation of bone marrow, high fever, increased heart rate
• osteomyelitis diagnosis: Blood cultures, pus cultures, and radiologic imaging to guide diagnosis
• streptococci: Gram-positive cocci that form pairs, short and/or long chains on staining
• streptococci

  catalase negative, non motile, facultative anaerobic, cultured on HBA
• S. pyogenes

  streptococci
• folliculitis

  superficial pustular inflammation of hair follicle, caused by bacteria gaining entry through abrasions, usually caused by s. aureus
• furuncles

  deep infection of hair follicle, pus filled, nodule can rupture spontaneously
• Carbuncles

  multiple boils, malaise and fever, caused by s. aureus
• impetigo

  pus forming infection, caused by s. aureus or s. pyrogens
• crusted impetigo

  yellow crusted ulcerative erosions, itchy
• bullous

  large blisters with fluid, blisters rupture easily, caused by s aureus
• erysipelas

  superficial infection of the skin, rapidly spreading, usually on lower extremities, fever, almost always caused by s. pyrogens
• people at risk for erysipelas

  infants, young children, older adults, immunocompromised
• cellulitis: Infection of the skin that extends into the dermis and often involves the subcutaneous tissue, can also be caused by fresh or salt water gram negative rods
• cellulitis infected sites

  tender and swollen, red, borders arent usually raised