Lecture 29 Objectives 1 Describe the structure of the skin and mucous membranes and the ways pathogens can invade the skin Structure and function Epidermis stratus corneum and keratin Dermis Secretions perspiration and sebum Portals of entry follicles ducts Subcutaneous layer Inhibits microbes by Perspiration and sebum contain nutrients salt inhibits microbes Lysozyme hydrolyzes peptidoglycan Fatty acids inhibit some pathogens Dry kearatin layer provides water proofing Defensins are antimicrobial peptides Sebum prevents growth AND can provide nutrients to microbes Mucous membranes Line body cavities The epithelial cells are attached to an extracellular matrix Cells secrete mucus Some cells have cilia Pathogens invade by Moist areas of the skin support more bacteria growth armpits Pathogens can enter through hair follicles sweat ducts oils glands 2 Provide examples of normal skin microbiota and state the general locations and ecological roles of its members Normal flora not normally removed by washing Mostly Gram positive cocci bacteria Staphylococcus Low GC Gram Streptococcus Low GC Gram Diphtheroids coryneforms High GC Gram Porpionibacterium metabolize oil and colonize on hair follicles Can withstand drying fatty acids low pH high salt Some yeasts malassezia fiurfur grow on oily secretions and can cause dandruff 3 Differentiate Staphylococci from Streptococci and name several skin infections caused by each Staphylococci Gram low GC cocci in clusters Coagulase an enzyme clots fibrin in blood majority of skin flora consists of coagulase neg S epidrmidis all pathogenic S aureus are Coagulase Pathogenic S aureus also produce extracellular enzymes and toxins Cause localized infections resulting from Staph a entering through openings in the skin Folliculitis furuncles boils carbuncles Toxemias occur when toxins enter bloodstream Scalded skin syndrome Toxic shock syndrome Folliculitis Infections of the hair follicles Sty e Folliculitis of an eyelash Furuncle Abscess pus surrounded by inflamed tissue Carbuncle Inflammation of tissue under the skin Impetigo new born highly contagious superficial skin infection staph a Streptococcus Gram Low GC cocci in chains Hemolysins beta alpha and gamma hemolysis Classified into groups according hemolytic enzymes and surface antigens Group A most important beta hemolytic Can cause severe and rapid tissue destruction Groups B C O Many virulence factors M protein extracellular enzymes and toxins M protein on surface anti complement anti phagocytosis Cause Impetigo isolated pustules Erysipelas reddish patches Skin infections Streptococcus pyogenes Many prophages carry virulence factors Erysipelas Caused by group A beta hemolytic Strep toxin Impetigo Isolated pustules become crusted Invasive group A strep Streptokinases Hyaluronidase Exotoxin A superantigen Cellulitis Necrotizing fasciitis flesh eating 4 List the causative agent mode of transmission and clinical symptoms of Pseudomonas dermatitis otitis externa and acne Pseudomonas aeruginosa characteristic blue green pus caused by pigment pyocyanin Produces an endotoxin and several exotoxins Gram negative rods Aerobes found primarily in soil and water and resistant to many disinfectants and antibiotics grow on traces of organic substance in soap liner adhesive Unusual metabolism Environmental soils and water Opportunists Cause Dermatitis self limiting 2 wks swimming pool sauna hot tub Wound and skin infections Otitis externa swimmer s ear Burn patient infections Quinolones are useful for treatment 5 List the causative agent mode of transmission and clinical symptoms of these skin infections warts smallpox chickenpox shingles cold sores measles rubella Viral skin infections Pseudomonas aeruginosa others Warts Papilloma virus Skin cells proliferate and produce benign growth spread by direct contact Fever blisters herpes simplex Herpes cold sores Cold sores result when laten herpes virus is activated HSV1 is transmitted orally and via respiratory routes Latency trigeminal ganglion Recurrent lesions Treated by acyclovir Chickenpox shingles VZV Herpes localized to skin cells producing reddish rash Latency dorsal root ganglion Painful dermal infections dermatomes Reactivation of latent VZV releases viruses that move along peripheral nerves to skin Shingles vesicular rash along the affected cutaneous sensory nerves Can be treated with acyclovir virus Pox Smallpox Variola Only host are humans transmitted via respiratory route and move to the skin via bloodstream Paramyxovirus rubeola Measles Transmitted through respiratory route Macular rash and Koplik s spots after virus attacks respiratory tracty Vaccination can give life long immunity Togavirus rubella German measles respiratory trct Macular rash and fever Congenital rubella syndrome causes severe fetal damage stillbirth deafness eye cataracts heart defects mental retardation Vaccination available live virus 6 Define conjunctivitis eye infection inflammation of the conjunctiva caused by infection injury or allergy can be transmitted by improperly disinfected contact lenses 7 List the causative agent mode of transmission and clinical symptoms of these eye infections neonatal gonorrheal ophthalmia inclusion conjunctivitis trachoma and herpetic keratitis A Neisseria gonorrhoeae Gram cocci 1 Neonatal gonorrheal ophthalmia 2 Ophthalmic ointment at birth Obtained during passage through birth canal B Chlamydia trachomatis 1 inclusion conjunctivitis 2 trachoma Trachoma scar tissue forms on cornea at birth swimming pool conjunctivitis Treated with antibiotics ointment unchlorinated water leading cause of blindness worldwide millions have the infection severe conjunctivitis nodules scarring of the cornea scars abrade the cornea leading to blindness Viral Conjunctivitis Herpes simplex 1 Adenovirus shipyard eye B Keratitis herpetic keratitis HSV 1 Infection of cornea may cause blindness trifluridine is effective Lecture 30 1 Define central nervous system and blood brain barrier The central nervous system CNS Brain Spinal cord The meninges three membranes Dura mater Arachnoid Pia mater The peripheral nervous system PNS 2 Differentiate meningitis from encephalitis Meningitis Inflammation of meninges The cerebrospinal fluid CSF in subarachnoid space The blood brain barrier The blood brain barrier capillaries prevents passage of some materials such as antimicrobial drugs from the blood into the CNS 3 Discuss meningitis caused by Haemophilus influenzae Neisseria
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