SKIN INFECTIONS

• Skin

  • the largest organ in the body
  • consists of an outer epidermis and inner epidermis
  • is a physical barrier that secretes antimicrobial chemicals, including acidic and salty secretions, waterproofing keratin, and sebum
• Normal skin flora

  • Propionibacterium acnes
  • Corynebacterium sp.
  • Staphylococci (Staphylococcus epidermidis, Staphylococcus aureus)
  • Streptococci sp.
  • Candida albicans (yeast)
• Folliculitis (Staphylococcus aureus)


  Skin abscess; encapsulated, so not reached by antibiotics
• Scalded skin syndrome (S. aureus)


  Vesicular lesions over entire skin surface, fever; most common in infants
• Scarlet fever (Streptococcus pyogenes)


  Sore throat, fever, rash caused by toxin; can lead to rheumatic fever and other complications
• Erisypelas (S. pyogenes)


  Skin lesions spread to systemic infection; rare today, but common and fatal before antibiotics were available
• Pyoderma and impetigo (Staphylococci, streptococci)


  Skin lesions, usually in children; easily spread by hands and fomites
• Acne (Propionibacterium acnes)


  Skin lesions caused by excess of male sex hormones; infection is secondary; common in teenagers
• Burn infections (Pseudomonas aeruginosa and other bacteria)


  Growth of bacteria under eschar, often a nosocomial infection; difficult to diagnose and treat; causative agents typically antibiotic-resistant
• Rubella (Rubella virus)


  Mild disease with maculopapular exanthema (discolored, pimply rash); infection early in pregnancy can lead to congenital rubella; vaccine has greatly reduced incidence
• Measles (Rubeola virus)


  Severe disease with fever, conjunctivitis, cough, and rash; encephalitis is a complication; occurs mainly in children; vaccine has greatly reduced incidence
• Roseola (Human herpesvirus 6)


  Sudden fever, followed by rose-colored rash; virus shed in saliva
• Chickenpox (Varicella-zoster virus)


  Generalized macular (discolored) skin lesions
• Shingles (Varicella-zoster virus)


  Pain and skin lesions, usually on trunk; occurs in adults with diminished immunity; susceptible children exposed to cases of shingles can develop chickenpox
• Smallpox (Smallpox virus)


  Eradicated by immunization as a human disease
• Other pox diseases (Other poxviruses)


  Clear or bluish vesicles on skin surfaces; human infections are rare
• Warts (Human papillomaviruses)


  are self-limiting; malignant warts occur in immunologic deficiencies; cause of 99% of cervical cancer
• Dermatomycoses (Dermatophytes)


  Dry, scaly lesions on various parts of the skin; difficult to treat
• Sporotrichosis (Sporothrix schenckii)


  Granulomatous, pus-filled lesions; sometimes disseminates to lungs and other organs
• Blastomycosis (Blastomyces dermatitidis)


  Granulomatous, pus-filled lesions that develop in lungs and wounds; sometimes disseminates to other organs
• Candidiasis (Candida albicans)


  Patchy inflammation of mucous membranes of the mouth (thrush) or vagina (vaginitis); disseminated nosocomial infections occur in immunodeficient patients
• Aspergillosis (Aspergillus species)


  Wound infection in immunodeficient patients; also infects burns, cornea, and external ear
• Zygomycosis (Mucor and Rhizopus species)


  Occurs mainly with untreated diabetes; begins in blood vessels and can rapidly disseminate
• Madura foot (Various soil fungi and actinomycetes)


  Initial lesions spread and become chronic and granulomatous; can require amputation
• Swimmer's itch (Cercariae of schistosomes)


  Itching due to cercariae burrowing into skin; immunological reaction prevents their spread
• Dracunculiasis (Dracunculus medinensis)


  Larvae ingested in crustaceans in contaminated water migrate to skin and emerge through lesion; juveniles cause severe allergic reactions