cph

• Skin

  • Rigid barrier due to keratin
  • Antimicrobial factors: salt, antimicrobial peptides, lysozomes, fatty acids, constant shedding
  • Microbial entrance typically through hair follicle & sweat glands
• Normal microbiota of the skin

  • Gram positive bacteria: Staphylococci, Micrococci, Corynebacteria, Propionibacteria
• Microbial diagnoses of the skin

  • Bacterial: Staphylococcus aureus, Streptococcus pyogenes, Pseudomonas aeruginosa, Propionibacterium acnes
  • Viral: Warts, Smallpox, Chickenpox, Shingles, Herpes simplex, Measles, Rubella, 5th disease, Roseola
  • Fungal: Candidiasis, Ringworm
  • Parasitic: Scabies, Lice, Bugs
• STAPHYLOCOCCAL SKIN INFX
• Staphylococcal skin infections

  • Folliculitis, Stye, Furuncle (boil), Abscess
• Staphylococcal scalded skin syndrome

  Also known as Ritter's disease, caused by phage encoded toxin TSST leading to exfoliation, occurs in kids under 2 years, causes toxemia
• Streptococcus pyogenes

  • Gram positive cocci in pairs, Catalase negative, Facultative anaerobe, Beta-hemolytic, Group A antigen, Produces M protein, streptolysin O, hyaluronidase, streptokinase, DNAse, erythrogenic toxin
• Streptococcal skin infections

  • Localized: Erysipelas, Impetigo
  • Invasive: Cellulitis, Necrotizing fasciitis
• Pseudomonas aeruginosa

  • Gram negative rod, Aerobic, Oxidase positive, Non-fermenter, Produces blue-green pus pigment pyocyanin
• Pseudomonas dermatitis

  Otitis externa transmitted through swimming water, treated with fluoroquinolones, also causes post-burn infections
• Types of acne

  • Comedonal acne, Inflammatory acne, Nodular cystic acne
• Acne pathogenesis

  P. acnes utilizes glycerol in sebum and produces fatty acids, Fatty acids are proinflammatory, Neutrophils are attracted further contributing to inflammation
• Acne treatments

  • Benzoyl peroxide, Antibiotics (erythromycin, clindamycin), Isotretinoin
• Teratomas

  Encapsulated tumor with tissue or organ components resembling normal derivatives of all 3 germ layers, also known as "monster"
• Gangrene

  Death of soft tissue due to loss of blood supply and tissue necrosis, can be gas gangrene caused by Clostridium perfringens
• Viral skin infections

  • Skin tumors (warts), Exanthems, Transmitted by aerosol leading to viremia and skin manifestation
• Warts

  Caused by Papillomaviruses, benign skin growths, some associated with cancer, transmitted by direct contact, treated by removal, interferon stimulation
• Poxviruses

  • Smallpox (Variola), Varicella-Zoster virus, Herpes Simplex 1, Measles, Rubella, 5th disease, Roseola
• Smallpox (Variola)


  Variola major has 20-30% mortality, Variola minor has <1% mortality, Vaccination has 15/1 million life threatening side effects and 1-2 deaths per 1 million, Emerging disease is Monkeypox, Orthopoxvirus transmitted from animals to humans
• Varicella-Zoster virus

  Causes chickenpox initially, transmitted by respiratory route, causes pus-filled vesicles, can remain latent in dorsal root ganglia and reactivate as shingles, routine vaccination available
• Herpes Simplex 1

  Can remain latent in trigeminal nerve ganglia, causes recurrent exacerbations of cold sores/fever blisters and herpes gladiatorum, treated with acyclovir
• Measles (Rubeola)


  Causes cold symptoms, fever, macular rash with raised spots and Koplik's spots, starts on face and spreads, prevented by vaccination
• Rubella (German measles)


  Caused by Rubella virus, causes macular rash and light fever, can cause severe congenital defects, prevented by vaccination
• 5th disease (Erythema infectiosum)


  Caused by Human parvovirus B19, causes mild flu-like symptoms and distinct "slapped face" skin rash
• Roseola

  Caused by HHV-6 and HHV-7, causes high fever followed by a rash lasting 1-2 days, virus can be found in saliva of most adults
• Cutaneous mycoses (fungal skin infections)


  • Dermatomycoses (Tinea/Ringworm), Candidiasis
• Dermatomycoses

  Fungi that colonize the outer epidermis, cause Tinea infections
• Types of Tinea infections

  • Tinea capitis (scalp), Tinea cruris (groin/jock itch), Tinea pedis (feet), Tinea unguium (nails)
• Candidiasis

  Caused by Candida albicans yeast, results from suppression of normal bacteria by antibiotics, can infect skin, mucous membranes, and cause thrush, treated topically with miconazole or nystatin, can become systemic requiring fluconazole
• Parasitic infestations of the skin

  • Protozoa, Helminths, Microscopic arthropods
• Scabies

  Caused by the Sarcoptes scabiei mite burrowing in the skin to lay eggs, causes intense itching and risk of superinfection, treated with topical permethrin insecticide, can be transmitted by intimate contact
• Types of Tinea (Ringworm)

  • TINEA CAPITIS - ringworm of scalp
  • TINEA CRURIS - ringworm of groin or jock itch
  • TINEA PEDIS - ringworm of feet
  • TINEA UNGUIUM - nails infected
• Candidiasis

  Infection caused by Candida albicans (yeast)
• Candidiasis

  • Result of suppression of bacteria by antibiotics
  • Occurs in skin, mucous membranes of genitourinary tract and mouth
  • Thrush is an infection of mucous membranes of mouth
  • Topical treatment with miconazole or nystatin
  • Very common cause of vaginitis
  • AIDS patients are prone to candidiasis
  • If Candida becomes systemic, drug of choice is FLUCONAZOLE
• Examples of parasitic organisms

  • Protozoa
  • Helminths
  • Microscopic arthropods
• Scabies

  Infestation by Sacroptes scabiei - tiny mite burrowing in skin to lay eggs
• Scabies

  • Intense local itching, can lead to superinfection
  • Treated with topical insecticides (PERMETHRIN)
  • Mite can be transmitted by intimate contact like sexual
  • Often seen in family members/nursing homes
• Pediculosis

  Infestation by lice
• Types of Pediculosis

  • PEDICULUS HUMANUS CAPITIS (head louse)
  • P.H. CORPORIS (body louse)
• Pediculosis

  • Head lice easily transferred by head-to-head contact, common in children
  • Body lice lay eggs (nits) on hair, treated with topical insecticides and combing out