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PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
MicrobiologyB.E Pruitt & Jane J. Stein
AN INTRODUCTIONEIGHTH EDITION
TORTORA • FUNKE • CASE
Chapter 21, part AMicrobial Diseases of the Skin and Eyes
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Skin
• Salt inhibits microbes• Lysozyme hydrolyzes
peptidoglycan• Fatty acids inhibit
some pathogens
Figure 21.1
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• Line body cavities• Epithelial cells attached to an extracellular matrix• Cells secrete mucus• Some have cilia
Mucous Membranes
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• Gram-positive, salt-tolerant bacteria• Staphylococci• Micrococci• Diphtheroids
Normal Microbiota of the Skin
Figure 14.1a
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• Exanthem• Skin rash arising from another focus of infection
• Enanthem• Mucous membrane rash arising from another
focus of infection
Microbial Diseases of the Skin
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Microbial Diseases of the Skin
Figure 21.2
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• S. epidermidis• Gram-positive cocci, coagulase-negative
• Staphylococcus aureus• Gram-positive cocci, coagulase-positive• Leukocidin• Exfoliative toxin
Staphylococcal Skin Infections
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Staphylococcal Skin Infections
Figure 21.3
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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
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Staphylococcal Skin Infections
• Impetigo of the newborn
• Toxemia
• Scalded skin syndrome
• Toxic shock syndrome
Figure 21.4
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• Streptococcus pyogenes
• Group A beta-hemolytic streptococci
• M proteins
Streptococcal Skin Infections
Figure 21.5
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• Erysipelas
• Impetigo
Streptococcal Skin Infections
Figure 21.6, 7
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• Streptokinases• Hyaluronidase• Exotoxin A,
superantigen• Cellulitis• Necrotizing fasciitis
Invasive Group A Streptococcal Infections
Figure 21.8
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• Pseudomonas aeruginosa• Gram-negative, aerobic rod• Pyocyanin produces a blue-green pus
• Pseudomonas dermatitis• Otitis externa• Post-burn infections
Infections by Pseudomonads
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Calculate the relative risk to determine the most likely source of Pseudmonas dermatitis
Exposure Exposed Not Exposed(a) Have
Rash(b) No Rash (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 = aa + b f = c
c + d Relative Risk = ef
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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
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• 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
Acne
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• Papillomaviruses• Treatment:
• Removal• Imiquimod (stimulate interferon production)• Interferon
Warts