Microbiology B.E Pruitt & Jane J. Stein AN INTRODUCTION EIGHTH EDITION TORTORA FUNKE CASE 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

Line body cavities GI / Respiratory / Urogenital Epithelial cells attached to an extracellular matrix Cells secrete mucus Some have cilia Mucous Membranes

Gram-positive, salt-tolerant bacteria Staphylococci S. epidermiditis Micrococci Diphtheroids Corynebacteria Normal Microbiota of the Skin Figure 14.1a

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 Microbial Diseases of the Skin

Figure 21.2

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

Staphylococcal Skin Infections Impetigo of the newborn Toxemia Scalded skin syndrome Toxic shock syndrome S. aureus and Mg +2 binding tampons Figure 21.4

Streptococcu s pyogenes Group A beta- hemolytic streptococci M proteins Catalase - Streptococcal Skin Infections Figure 21.5

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 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 school- age children, especially in the summer months.Group A streptococcusStaphylococcus aureus Streptococcal Skin Infections Figure 21.6, 7

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

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

Calculate the relative risk to determine the most likely source of Pseudmonas dermatitis ExposureExposedNot Exposed (a) Have Rash(b) No Rash(c) Have Rash(d) No Rash Restaurant Arcade10696 Swimming pool Exercise room11587 Hot tub e = a a + b f = c c + d Relative Risk = efef

What was the mostly likely source of this outbreak of Pseudmonas dermatitis? ExposureRelative Risk Restaurant1.24 Arcade1.04 Swimming pool6.14 Exercise room1.29 Hot tub9.90

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

Papillomaviruses Treatment: Removal Imiquimod Aldara (stimulate interferon production) Interferon Laser Acid freezing Warts