Chapter.21

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Chapter.21

  1. 1. Chapter 21: Microbial Disease of the skin and eyes <ul><li>1. Skin is composed of: </li></ul><ul><li>a. epidermis – a thin outer layer with a waterproof protein called keratin </li></ul><ul><li>b. dermis = a thick inner layer </li></ul><ul><li>2. Hair follicles, sweat glands and oil ducts in the dermis are portals of entry for microbes to penetrate deeper tissue </li></ul><ul><li>3. Skin has a high salt content and little moisture so normal microbiota must be able to tolerate salt and be resistant to drying </li></ul>
  2. 2. : Microbial Disease of the skin and eyes <ul><li>4. Skin’s normal microbiota are large numbers of gram positive bacteria </li></ul><ul><li>ex. Staphylococcus, Micrococcus, Propionibacterium , Corynebacterium </li></ul>
  3. 3. Microbial Diseases of the skin <ul><li>1. Rashes and lesions on the skin can be from systemic diseases rather than skin infections, the lesions can be useful in helping to dx the disease </li></ul><ul><li>Pg 616 </li></ul><ul><li>a. vesicles = small, fluid filled lesions </li></ul><ul><li>b. bullae = vesicles > 1 cm in diameter </li></ul><ul><li>c. macules = flat, reddened lesions </li></ul><ul><li>d. papules = raised lesions </li></ul><ul><li>e. pustules = papules that contain pus </li></ul>
  4. 4. Bacterial Disease of the Skin <ul><li>Include Staphylococcal, Streptococcal, and pseudomonad infections – most are opportunistic pathogens that enter through cuts, burns or surgical incisions </li></ul><ul><li>Staphylococcus – Staph infections are very difficult to treat </li></ul><ul><ul><li>Vancomycin is the only Ab that S. aureus isn’t resistant to – used for MRSA </li></ul></ul><ul><ul><ul><li>1) Methicillin resistant staph – leading cause of nosocomial infections in US. </li></ul></ul></ul>
  5. 5. Bacterial Disease of the Skin <ul><li>3. Staphylococcus is divided into coagulase positive and coagulase negative bacteria </li></ul><ul><li>a. coagulase positive – produce an enzyme coagulase that clots fibrin in blood </li></ul><ul><li>1) S. aureus – most pathogenic of the Staphylococci </li></ul><ul><li>2) fibrin clots protect against phagocytosis and other host defenses </li></ul>
  6. 6. Bacterial Disease of the Skin <ul><ul><li>3. b. coagulase negative – produce biofilms on surfaces they adhere to such as catheters </li></ul></ul><ul><ul><li>1) ex. Staphylococcus epidermidis – normal microbiota of skin is pathogenic when skin barrier is broken such as insertion/removal of catheter </li></ul></ul>
  7. 7. Bacterial Disease of the Skin <ul><li>4. Staphylococcus aureus – normal microbiota of skin, nose, throat </li></ul><ul><li>a. folliculitis – infection of hair follicles – pimples, sty, furuncle (boil) </li></ul><ul><li>1) a boil is a type of abscess, Abs don’t penetrate abscesses well, need to drain pus first </li></ul><ul><li>2) if the body doesn’t wall of a furuncle it invades the surrounding tissue and becomes a carbuncle – px has fever, generalized symptoms of disease </li></ul>
  8. 8. Bacterial Disease of the Skin <ul><li>4. b. impetigo – vesicles on skin that rupture and then crust over </li></ul><ul><li>1) also caused by Streptococcus pyogenes </li></ul>
  9. 9. Impetigo
  10. 10. Bacterial Disease of the Skin <ul><li>4. c. Toxic shock syndrome – can be life threatening, fever, vomiting, sunburn like rash followed by shock and organ (esp. kidney) failure </li></ul><ul><li>1) some cases from absorbent tampon use left in too long </li></ul><ul><li>2) most cases from nasal surgery where absorbent packing is used, from surgical incisions, after child birth </li></ul>
  11. 11. Bacterial Disease of the Skin <ul><li>Streptococcal Skin Infections </li></ul><ul><li>Streptococci – G+, spherical bacteria that grows in chains </li></ul><ul><li>Secrete toxins and enzymes that vary w/ species </li></ul><ul><ul><li>Hemolysins = toxins wh/ lyse RBCs </li></ul></ul><ul><ul><ul><li>Streptococci are categorized as alpha, beta, or gamma-hemolytic depending on the type of Hemolysins they produce </li></ul></ul></ul><ul><ul><ul><li>Beta hemolytic streptococci are associated w/ human disease </li></ul></ul></ul>
  12. 12. Bacterial Disease of the Skin <ul><li>2. b. Beta hemolytic streptococci are also differentiated into serological groups A-T based on a CH2O found on the cell wall </li></ul><ul><li>a. group A streptococci (GAS) are the most important of the beta hemolytic group ex. Streptococcus pyogenes </li></ul><ul><li>b. GAS produce substances that aid in rapid spread of infection </li></ul>
  13. 13. Bacterial Disease of the Skin <ul><li>3. Streptococcus pyogenes </li></ul><ul><li>a. impetigo </li></ul><ul><li>b. cellulitis – attacks solid tissue </li></ul><ul><li>c. myositis – attacks muscle </li></ul><ul><li>d. necrotizing fasciitis = flesh eating disease – attacks fascia = muscle coverings </li></ul>
  14. 14. Necrotizing fasciitis
  15. 15. Necrotizing fasciitis
  16. 16. Bacterial Disease of the Skin <ul><li>4. Pseudomonads – G neg rods, most common = Pseudomonas aeruginosa </li></ul><ul><li>a. opportunistic pathogen </li></ul><ul><li>b. produces several exotoxins and has an endotoxin </li></ul><ul><li>c. grows in biofilms – causes nosocomial infections from medical tubes, etc. </li></ul><ul><li>d. common pathogen in burn pxs – can produce blue green pus – color of bacterial pigment = pyocyanin </li></ul>
  17. 17. Viral Disease of the Skin <ul><li>Warts = papillomas – transmitted person to person by contact, sexually </li></ul><ul><ul><li>Incubation period several weeks after infection </li></ul></ul><ul><ul><li>Tx = cryotherapy, electrical current, burn with acids, laser tx but virus can become aerosol </li></ul></ul><ul><ul><li>Genital warts (human papilloma) – HPV 16 associated w/ cervical cancer </li></ul></ul>
  18. 18. Genital Warts
  19. 19. Warts
  20. 20. Viral Disease: Smallpox <ul><li>2. Smallpox (Variola) – Variola major – virulent – 20% mortality, variola minor < 1% mortality </li></ul><ul><li>a. transmitted by respiratory route – airborne </li></ul><ul><li>b. early signs – high fever, fatigue, HAs, backaches </li></ul><ul><li>c. infect internal organs before going to bloodstream and then skin rxs </li></ul>
  21. 21. Viral Disease: Smallpox <ul><li>2.d. initial macular rash wh/ becomes pustules in approximately 10 days </li></ul><ul><li>e. 1 st disease for wh/ a vaccine was developed and 1 st disease eradicated 1977 WHO </li></ul><ul><li>f. only 2 sites w/ virus – US and Russia </li></ul><ul><li>g. similar disease = monkeypox – can jump from animals to humans, endemic to Africa, E. Asia – monkeys, small animals </li></ul><ul><li>h. humans are the only reservoir source </li></ul>
  22. 23. Smallpox distribution on body
  23. 24. Smallpox
  24. 25. Chickenpox (Varicella) <ul><li>Is a DNA virus that is highly contagious before the rash breaks out </li></ul><ul><li>Mild , childhood disease with a low mortality rate which are usually from encephalitis or pneumonia </li></ul><ul><li>Portal of entry = respiratory system, transmitted by droplets or fluid in vesicles a. localizes in skin cells in 2 weeks </li></ul><ul><li>Is a herpesvirus – Varicella - zoster </li></ul>
  25. 26. Chickenpox (Varicella) <ul><li>5. Early signs are fever, HA, body ache followed by an itchy rash </li></ul><ul><li>6. Vesicles form for 3 – 4 days, fill with pus, rupture, and form a scab </li></ul><ul><li>7. Lesions on face, throat, back and can go on shoulders and chest </li></ul><ul><li>8. Can cause fetal damage if contracted during early pregnancy, Crosses placenta </li></ul><ul><li>9. live, attenuated vaccine – effectiveness declines with time wh/ may lead to a population of susceptible adults </li></ul>
  26. 27. Chickenpox
  27. 28. Reye’s Syndrome <ul><li>Caused by complications of chickenpox, influenza, or aspirin intake of a child or teenager </li></ul><ul><li>After the initial infection has gone the patient has persistent vomiting, drowsiness, and combative behavior (brain dysfunction) </li></ul><ul><li>Coma and death can follow – 30% death rate </li></ul><ul><li>Survivors may have neurological damage </li></ul>
  28. 29. Shingles (Herpes Zoster) <ul><li>All herpesviruses can remain latent in the body </li></ul><ul><li>After a primary infection the virus retreats up the peripheral nerves to the dorsal root ganglion (pg. 625) where it can remain dormant for decades </li></ul><ul><li>The virus can be re-activated and move down the peripheral nerves to the sensory nerves of the skin where the outbreak is in the form of shingles </li></ul>
  29. 30. Shingles <ul><li>4. Shingles follow the dermatome level of the nerve they were on and are usually unilateral </li></ul><ul><li>5. A dermatome is the band of skin innervated by the sensory nerve root of a single spinal segment </li></ul><ul><li>6. Infection causes burning, stinging pain that can last for month or years </li></ul>
  30. 31. Shingles <ul><li>7. People that haven’t had chickenpox can contract them when exposed to shingles </li></ul><ul><li>8. You usually don’t get shingles more than once </li></ul><ul><li>9. In immunocompromised patients – 17% mortality rate </li></ul>
  31. 32. Dermatome Patterns
  32. 33. Shingles on a young px
  33. 34. Shingles – Herpes Zooster
  34. 35. Herpes simplex – DNA virus <ul><li>Herpesvirus 1 – transmitted oral and respiratory routes </li></ul><ul><ul><li>Lesions = cold sores or fever blisters are vesicles near the outer margin of the lips </li></ul></ul><ul><ul><li>Remains latent in the trigeminal nerve ganglia </li></ul></ul><ul><ul><ul><li>1) re-occurrence is triggered by UV light, emotional upsets, hormonal changes </li></ul></ul></ul>
  35. 36. Herpes simplex – DNA virus <ul><li>2. Herpesvirus 2 – transmitted by sexual contact, causes genital herpes </li></ul><ul><li>a. remains latent in the sacral nerve ganglia near the base of the spine </li></ul><ul><li>b. risk of miscarriage, cervical cancer </li></ul><ul><li>3. Rare – herpesvirus 1 or 2 can spread to the brain causing encephalitis </li></ul>
  36. 37. Herpes simplex 1
  37. 38. Measles (Rubeola) <ul><li>An RNA virus that is Spread by respiratory route and is highly contagious </li></ul><ul><li>Humans are the only reservoir source </li></ul><ul><li>MMR vaccine = measles, mumps, rubella – almost eliminated measles in US but there are 1 million deaths a year worldwide </li></ul><ul><ul><li>a. Most cases now are in children under 1 year old because they don’t get the vaccine until age 1 and mother’s vaccinated Abs aren’t strong enough to give passive immunity to infants like Abs from recovering from the disease </li></ul></ul>
  38. 39. Measles (Rubeola) <ul><li>4. Incubation period of 10 – 12 days and then symptoms develop resembling a common cold </li></ul><ul><li>5. A macular rash appears on the face and spreads to the trunk and extremities </li></ul><ul><li>6. Diagnostic indicator is the presence of Koplik’s spots in the mucous membranes of the mouth ( lesions with a white necrotic center) </li></ul>
  39. 40. Measles (Rubeola) <ul><li>6. Complications are middle ear infection, pneumonia, encephalitis </li></ul><ul><li>7. A rare complication is subacute sclerosing panencephalitis which appears 1 – 10 years after recovery </li></ul><ul><li>a. it is a progressive degenerative disease of the CNS which is fatal within a few yrs </li></ul>
  40. 41. Rubella <ul><li>Is a RNA virus </li></ul><ul><li>Aka German measles and 3 day measles </li></ul><ul><li>Milder viral disease than rubeola (measles) </li></ul><ul><li>Transmission is by respiratory route, secretions and occasionally urine </li></ul><ul><li>Incubation period of 2-3 weeks </li></ul>
  41. 42. Rubella <ul><li>6. Sxs = light fever, macular rash that 1 st appears on the face and progresses down the trunk to the extremities, resolves in 3 days </li></ul><ul><li>7. Problem is if pregnant female in the 1 st trimester contracts Rubella – there is a 35% chance of serious fetal damage </li></ul><ul><li>a. Congenital Rubella Syndrome = deafness, eye cataracts, heart defects, mental retardation, death – 15% of babies with the defect die within the 1 st year of life </li></ul>
  42. 43. Rubella
  43. 44. Fungal Disease = mycosis <ul><li>Cutaneous mycosis = fungus of hair, nails, outer layer of epidermis, grow on keratin </li></ul><ul><ul><li>Aka Dermatophytes, tinea, ringworm </li></ul></ul><ul><ul><li>tinea capitis = ringworm of the scalp, contact with fomites, dogs, cats </li></ul></ul><ul><ul><li>tinea cruris = ringworm of the groin, aka jock itch </li></ul></ul><ul><ul><li>tinea pedis = ringworm of the feet, aka athlete’s foot </li></ul></ul><ul><ul><li>E. tinea corporis = ringworm of body </li></ul></ul>
  44. 45. Fungal Disease <ul><li>2. 3 genera of Cutaneous mycosis </li></ul><ul><li>a. Trichophyton – infects hair, skin, nails </li></ul><ul><li>b. Microsporum – hair, skin </li></ul><ul><li>c. Epidermophyton – skin, nails </li></ul><ul><li>d. tx. Topical drugs ,oral griseofulvin – potential severe side effects </li></ul><ul><li>3. Subcutaneous mycosis – more serious, usually inhabit the soil </li></ul><ul><li>a. most common disease = sporotrichosis – caused by dimorphic fungi Sporothrix schenchii - forms small ulcer on hands and enters the lymphatic system </li></ul>
  45. 46. Ringworm on dog
  46. 47. Ringworm
  47. 48. Fungal Disease <ul><li>4. Candidiasis – from overgrowth if yeast Candida albicans </li></ul><ul><li>a. antibiotic therapy can cause </li></ul><ul><li>b. causes vaginitis, thrush (mouth) in newborns – no normal microbiota yet </li></ul><ul><li>c. immunosuppressed patients, obese, diabetics are prone to </li></ul>
  48. 49. Candida albicans
  49. 50. Candida albicans - thrush
  50. 51. Parasitic infection of the skin <ul><li>Scabies – caused by a mite = Sarcoptes scabiei which burrows under the skin to lay eggs </li></ul><ul><ul><li>Causes intense itching </li></ul></ul><ul><ul><li>Transmitted by direct contact including sexual contact </li></ul></ul><ul><ul><li>Tx is with topical and oral medication </li></ul></ul>
  51. 52. Scabies on skin
  52. 53. Mites on skin cells
  53. 54. Parasitic infection of the skin <ul><li>2. Pediculosis – infestation by lice </li></ul><ul><li>a. head louse = Pediculus humanus capitis </li></ul><ul><li>b. body louse = Pediculus humanus corporis – only body louse spreads disease ex. Epidemic typhus </li></ul><ul><li>c. lice need a blood meal from their host several times a day </li></ul><ul><li>1) after several weeks host becomes sensitized to louse saliva resulting in itching, s cratching can cause a secondary infection </li></ul>
  54. 55. Head louse
  55. 56. Pediculosis pubis
  56. 57. Louse Nit on hair shaft
  57. 58. <ul><li>Finish ob board </li></ul>

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