1/26/2016 Microbes Skin is the body's first line of defense against pathogens Invisible Invaders Almost impossible for Amazing Allies pathogens to penetrate Inhospitable environment skin secretions are acidic little moisture Chapter 21 commor Microbial Diseases of the Skin and or nose of healthy people Eyes Structure and Function of the Skin Structure and Function of the Skin Learning Objective Epidermis:thin outer portion of skin; Describe the structure of the skin and mucous composed of layers of epithelial cells membranes and the ways pathogens can Keratin:waterproofing protein coating invade the skin. outer layer of epidermis Dermis:inner,thick portion of skin; composed mainly of connective tissue
1/26/2016 1 Invisible Invaders Amazing Allies Chapter 21 Microbial Diseases of the Skin and Eyes • Skin is the body’s first line of defense against pathogens • Almost impossible for pathogens to penetrate • Inhospitable environment - skin secretions are acidic Staphylococcus aureus – common inhabitant of the skin or nose of healthy people - little moisture Structure and Function of the Skin Learning Objective Describe the structure of the skin and mucous membranes and the ways pathogens can invade the skin. Structure and Function of the Skin • Epidermis: thin outer portion of skin; composed f l f ith li l ll d of layers of epithelial cells • Keratin: waterproofing protein coating outer layer of epidermis • Dermis: inner, thick portion of skin; composed mainly of connective tissue
1/26/2016 erector musc Structure of Hair shaft Structure and Function of the Skin human skin Perspiration provides moisture and nutrients for bacterial growth Two parts: Dermis -Contains salt that inhibits microorganisms Epidermis -Contains lysozyme that breaks down bacterial cell walls Passage-ways for -Contains antimicrobial peptides ens: Sebum a mixture of lipids,proteins and salts is nd ducts secreted by oil glands to prevent skin and hair from drying out -Contains fatty acids that inhibit microbes -Contains nutrients for their growth as well aticn) Mucous Membranes Mucous Membranes Line the body cavities open to the exterior Mucus Tightjunctions ‘mam妆icells -Cells secrete mucus Some cells have cilia Often acidic,which limits the microbial Epithelial cell population Normal flora produce fatty acids from sebum Membrane of tied together by Often folded to maximize surface area
1/26/2016 2 Hair follicle Oil gland (produces sebum) Hair erector muscle Hair shaft Stratum corneum Sweat pore Epidermis Structure of human skin Two parts: Dermis Keratin Epidermis Dermis Epidermis Passage-ways for pathogens: Hair follicles Oil gland ducts Subcutaneous layer Duct of sweat gland Sweat gland (produces perspiration) Blood vessels Nerve Adipose tissue (fat) Oil gland ducts Sweat gland ducts Structure and Function of the Skin • Perspiration provides moisture and nutrients for bacterial growth – Contains salt that inhibits microorganisms – Contains lysozyme that breaks down bacterial cell walls – Contains antimicrobial peptides • Sebum a mixture of lipids, proteins and salts is secreted byg p oil glands to prevent skin and hair from drying out – Contains fatty acids that inhibit microbes – Contains nutrients for their growth as well Mucous Membranes • Line the body cavities open to the exterior • Tightly packed epithelial cells attached to an extracellular matrix – Cells secrete mucus – Some cells have cilia • Often acidic, which limits the microbial population - N rm l fl r pr duce f tt cids fr m sebum Normal flora produce fatty acids from sebum • Membrane of eyes washed by tears containing lysozyme, which destroys cell walls of certain bacteria • Often folded to maximize surface area Mucous Membranes
1/26/2016 Some mucosal cells have cilia. Folds of the intestinal mucosa In the respiratory system,the mucous layer traps microbes and the cilia sweep these particles upward and out of the body Blood etwork folds Submucosa Circular muscle Duodenal Top of ular old Normal Microbiota of the Skin Normal Microbiota of the Skin Resistant to drying and high salt Learning Objective concentration Provide examples of normal skin microbiota Large numbers of gram-positive cocci and state the general locations and -Staphylococci ecological roles of its members. -Micrococci Areas with moisture have higher populations -Metabolize sweat and contribute to body odor
1/26/2016 3 Some mucosal cells have cilia. In the respiratory system, the mucous layer traps microbes and the cilia sweep these particles upward and out of the body Folds of the intestinal mucosa Normal Microbiota of the Skin Learning Objective Provide examples of normal skin microbiota, and state the general locations and ecological roles of its members. Normal Microbiota of the Skin • Resistant to drying and high salt concentration • Large numbers of gram-positive cocci – Staphylococci – Micrococci • Areas with moisture have higher populations – Metabolize sweat and contribute to body odor
1/26/2016 Normal Microbiota of the Skin Microbial Diseases of the Skin Gram-positive pleomorphic rods (diphtheroids) Learning Objectives -Propionibacterium acnes inhabits hai follicles:anaerobic:lives on sebum Differentiate staphylococci from Produces acids that maintain low skin pH streptococci,and name several skin Corynebacterium xerosis occupies the infections caused by each. skin surface:aerobic List the causative agent,mode of yeast transmission,and clinical symptoms of -Malassezia furfur:causes dandruff Pseudomonas dermatitis,otitis externa, -Dandruff shampoos contain an and acne. this yeast Microbial Diseases of the Skin Microbial Diseases of the Skin Learning Objective Learning Objectives List the causative agents,modes of Differentiate cutaneous from subcutaneous mycoses and provide an transmission,and symptoms of warts, smallpox,monkeypox,chickenpox, example of each. shingles,cold sores,measles,and List the causative agent and predisposing rubella factors for candidiasis. List the causative agent,mode of transmission,clinical symptoms,and treatment for scabies and pediculosis
1/26/2016 4 Normal Microbiota of the Skin • Gram-positive pleomorphic rods (diphtheroids) – Propionibacterium acnes inhabits hair follicles; anaerobic; lives on sebum • Produces acids that maintain low skin pH – Corynebacterium xerosis occupies the skin surface; aerobic • Yeast – Malassezia furfur; causes dandruff – Dandruff shampoos contain an antibiotic against this yeast Microbial Diseases of the Skin Learning Objectives Differentiate staphylococci from streptococci, and name several skin infections caused by each. List the causative agent, mode of transmission, and clinical symptoms of Pseudomonas dermatitis, otitis externa, and acne. Microbial Diseases of the Skin Learning Objective List the causative agents, modes of transmission, and symptoms of warts, smallpox, monkeypox, chickenpox, shingles, cold sores, measles, and rub ll e a. Microbial Diseases of the Skin Learning Objectives Differentiate cutaneous from subcutaneous mycoses and provide an example of each. List the causative agent and predisposing factors for candidiasis. List the causative agent, mode of transmission, clinical symptoms, and treatment for scabies and pediculosis
1/26/2016 Microbial Diseases of the Skin Skin lesions 1 cm 【1cm Fluid Epidermis Important to understand terms that describe rashes Dermis Vesicles:small,fluid-filled lesions Vesicle-small,fluid Bulla-larger fluid filled Bullae:vesicles larger than 1 cm in diameter filled lesion Macules:flat,reddened lesions Papules:raised lesions Pustules:raised lesions with pus Exanthem:skin rash arising from a disease Enanthem:rash on mucous membranes arising from a i Pustule disease contains pus Staphylococcal Skin Infections Staphylococcal Skin Infections Staphylococci -Spherical gram-positive bacteria:form irregular clusters Staphylococcus epidermidis -90%of normal skin microbiota -Many produce coagulase Enzyme that clots fibrin in the blood -Healthcare-associated pathogen Used to identify types of staphylococci -Pathogenic when skin is broken or invaded -Produces biofilm on catheters protecting them from desiccation and disinfectants -Coagulase-negative
1/26/2016 5 Microbial Diseases of the Skin Many rashes and lesions are due to systemic diseases affecting internal organs and not infection of the skin. Important to understand terms that describe rashes • Vesicles: small, fluid-filled lesions • Bullae: vesicles larger than 1 cm in diameter • Macules: flat, reddened lesions • Papules: raised lesions • Pustules: raised lesions with pus • Exanthem: skin rash arising from a disease • Enanthem: rash on mucous membranes arising from a disease Epidermis 1 cm Fluid D i 1 cm Fluid Skin lesions Dermis Vesicle – small, fluid filled lesion Bulla – larger fluid filled lesion 1 cm 1 cm Pus Macule – flat lesion that is often reddish Pustule (papule) – raised lesion that contains pus Staphylococcal Skin Infections • Staphylococci – Spherical gram-positive bacteria; form irregular clusters – Many produce coagulase • Enzyme that clots fibrin in the blood • Used to identify types of staphylococci Staphylococcal Skin Infections • Staphylococcus epidermidis – 90% f l k b % of normal skin microbiota – Healthcare-associated pathogen – Pathogenic when skin is broken or invaded – Produces biofilm on catheters protecting them from desiccation and disinfectants – Coagulase-negative