Transcript Chapter 21a
TORTORA • FUNKE • CASE Microbiology AN INTRODUCTION EIGHTH EDITION B.E Pruitt & Jane J. Stein Chapter 21, part A Microbial Diseases of the Skin and Eyes Skin First line of defense • Salt inhibits microbes • Lysozyme hydrolyzes peptidoglycan • Fatty acids (from sebum) inhibit some pathogens • Dry • Layers slough off • UV Figure 21.1 Mucous Membranes • Line body cavities GI / Respiratory / Urogenital • Epithelial cells attached to an extracellular matrix • Cells secrete mucus • Some have cilia Normal Microbiota of the Skin • Gram-positive, salt-tolerant bacteria • Staphylococci • S. epidermiditis • Micrococci • Diphtheroids • Corynebacteria Figure 14.1a Microbial Diseases of the Skin • Exanthem • An exanthem is a rash that "bursts forth or blooms" towards the end of some infections. • Skin rash arising from another focus of infection • Enanthem • Mucous membrane rash arising from another focus of infection QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Microbial Diseases of the Skin Figure 21.2 Staphylococcal Skin Infections • S. epidermidis • Gram-positive cocci, coagulase-negative • Staphylococcus aureus • Gram-positive cocci, coagulase-positive • Leukocidin • Exfoliative toxin Staphylococcal Skin Infections Figure 21.3 Staphylococcal Skin Infections QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Folliculitis • Infections of hair follicles QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Sty • Folliculitis of an eyelash QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Furuncle • Abscess; pus surrounded by inflamed tissue • Carbuncle • Inflammation of tissue under the skin QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Staphylococcal Skin Infections • • • • Impetigo of the newborn Toxemia Scalded skin syndrome Toxic shock syndrome • S. aureus and Mg+2 binding tampons Figure 21.4 Streptococcal Skin Infections • Streptococcu s pyogenes • Group A betahemolytic streptococci • M proteins • Catalase Figure 21.5 Streptococcal Skin Infections • Erysipelas • An erysipelas skin lesion typically has a raised border that is sharply demarcated from normal skin. The underlying skin is painful, intensely red, hardened (indurated), swollen, and warm • Impetigo QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Impetigo is a skin infection that is generally caused by one of two bacteria: Group A streptococcus or Staphylococcus aureus. Impetigo usually affects preschool- and schoolage children, especially in the summer months. Figure 21.6, 7 Invasive Group A Streptococcal Infections • Streptokinases • Hyaluronidase • Exotoxin A, superantigen • Cellulitis • Necrotizing fasciitis Figure 21.8 Infections by Pseudomonads QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. • Pseudomonas aeruginosa • Gram-negative, aerobic rod • Pyocyanin produces a blue-green pus • Pseudomonas dermatitis • Otitis externa • Post-burn infections Calculate the relative risk to determine the most likely source of Exposure Exposed Not Exposed Pseudmonas (a) Have Rash (b) No Rash dermatitis (c) Have Rash (d) No Rash Restaurant 18 11 1 1 Arcade 10 6 9 6 Swimming pool 17 1 2 11 Exercise room 11 5 8 7 Hot tub 18 2 1 10 e= a a+b f= c c+d Relative Risk = e f What was the mostly likely source of this outbreak of Pseudmonas dermatitis? Exposure Relative Risk Restaurant 1.24 Arcade 1.04 Swimming pool 6.14 Exercise room 1.29 Hot tub 9.90 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 Warts • Papillomaviruses • Treatment: • Removal • • • • • Imiquimod Aldara (stimulate interferon production) Interferon Laser Acid freezing QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.