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Chapter 21, part A

Chapter 21, part A. Microbial Diseases of the Skin and Eyes. Skin. Salt inhibits microbes Lysozyme hydrolyzes peptidoglycan Fatty acids inhibit some pathogens. Figure 21.1. Mucous Membranes. Line body cavities Epithelial cells attached to an extracellular matrix Cells secrete mucus

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Chapter 21, part A

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  1. Chapter 21, part A Microbial Diseases of the Skin and Eyes

  2. Skin • Salt inhibits microbes • Lysozyme hydrolyzes peptidoglycan • Fatty acids inhibit some pathogens Figure 21.1

  3. Mucous Membranes • Line body cavities • Epithelial cells attached to an extracellular matrix • Cells secrete mucus • Some have cilia

  4. Normal Microbiota of the Skin • Gram-positive, salt-tolerant bacteria • Staphylococci • Micrococci • Diphtheroids Figure 14.1a

  5. Microbial Diseases of the Skin • Exanthem • Skin rash arising from another focus of infection • Enanthem • Mucous membrane rash arising from another focus of infection

  6. Microbial Diseases of the Skin Figure 21.2

  7. Staphylococcal Skin Infections • S. epidermidis • Gram-positive cocci, coagulase-negative • Staphylococcus aureus • Gram-positive cocci, coagulase-positive • Leukocidin • Exfoliative toxin

  8. Staphylococcal Skin Infections Figure 21.3

  9. Staphylococcal Skin Infections • Folliculitis • Infections of hair follicles • Sty • Folliculitis of an eyelash • Furuncle • Abscess; pus surrounded by inflamed tissue • Carbuncle • Inflammation of tissue under the skin

  10. Staphylococcal Skin Infections • Impetigo of the newborn • Toxemia • Scalded skin syndrome • Toxic shock syndrome Figure 21.4

  11. Streptococcal Skin Infections • Streptococcus pyogenes • Group A beta-hemolytic streptococci • M proteins Figure 21.5

  12. Streptococcal Skin Infections • Erysipelas • Impetigo Figure 21.6, 7

  13. Invasive Group A Streptococcal Infections • Streptokinases • Hyaluronidase • Exotoxin A, superantigen • Cellulitis • Necrotizing fasciitis Figure 21.8

  14. Infections by Pseudomonads • Pseudomonas aeruginosa • Gram-negative, aerobic rod • Pyocyanin produces a blue-green pus • Pseudomonas dermatitis • Otitis externa • Post-burn infections

  15. Calculate the relative risk to determine the most likely source of Pseudmonas dermatitis a a + b c c + d e f e = f = Relative Risk =

  16. What was the mostly likely source of this outbreak of Pseudmonas dermatitis?

  17. Acne • Comedonal acne • Occurs when sebum channels are blocked with shed cells • Inflammatory acne • Propionibacterium acnes • Gram-positive, anaerobic rod • Treatment: • Preventing sebum formation (isotretinoin) • Antibiotics • Benzoyl peroxide to loosen clogged follicles • Visible (blue) light (kills P. acnes) • Nodular cystic acne • Treatment: isotretinoin

  18. Warts • Papillomaviruses • Treatment: • Removal • Imiquimod (stimulate interferon production) • Interferon

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