LS-MCRB 121 1st Edition Exam# 4 Study GuideChapters 21, 22, 23, 24, 25Skin: Characteristics of Bacterial Skin PathogensPathogen GroupShape Gram (+/-) Toxins Capsule Misc.Staphylococcus Cocci + TSST-1 Yes Coagulase +/-CapsulesStreptococcus Cocci + Hemolysins, Streptolysins,Hyaluronidase,Streptokinases,Exotoxin AYes M protein and prevention of complement and phagocytosisPseudomonas Bacillus - Exotoxins and EndotoxinsOpportunisticpathogenTerms:- Coagulase: enzyme that clots blood- Staphylococcus epidermidis: gram-positive cocci, coagulase-negative- Staphylococcus aureus: gram-positive cocci, coagulase-positiveStaphylococcal Skin InfectionsDisease Pathogen Infection Site and AppearanceFolliculitis Staphylococcus aureus Hair folliclesSty S. aureus Folliculitis of an eyelashFuruncle S. aureus Abscess; severe form of folliculitis that results in pus surrounded by inflamed tissueCarbuncle S. aureus Inflammation of tissue under the skin, more deep than furuncleNonbullous Impetigo S. aureus Crusting (nonbullous) sores, spread by autoinoculationToxic Shock Syndrome (TSS) S. aureus Caused by TSST-1 that enters the blood stream. First discovered as a result of ahighly absorbent tampon, alsocaused by nasal surgeryScalded Skin Syndrome (Bullous Impetigo)S. aureus Toxins that causes skin cells toexfoliate or separate (Exfoliative Toxin-A). Most common in children under two, impetigo of the newbornS. aureus Virulence Determinants- Produce several proteins and toxins that:o Prevent phagocytosiso Immobilize neutrophilso Kill phagocytes (neutrophils)o Form clots (helpful in establishing an abscess)o Induce vomiting and diarrheao Trigger scalded skin syndromeo Cause toxic shock syndrome: life threatening condition with fever, vomiting, organ failure, rashStreptococcal Pathogenesis- Streptococci: grow and secrete toxins such as hemolysinso Categorized by Serological Groups antigens (A-T) based on surface carbohydrate antigenic structureo Can be deadly, divided into 80 antigenic types based on M protein- B-hemolytic Streptococci: most frequently associated with diseaseo Exception: alpha-hemolytic Strep. Pneumoniae- Group A Strep (GAS): synonymous with strep. Pyogenes- Important Strep toxins and their surface proteinso M protein: involved in adherence, complement activation, and phagocytic avoidanceo Hyaluronic acid capsule: anti-phagocytic, masks bacterium due to resemblance ofhuman connective tissueo Streptokinases: dissolve blood clotso Hyaluronidase: degrades connective tissueo DNase: degrades DNAo Streptolysins: lyse RBCs and poison neutrophilsStreptococcal Skin DiseasesDisease Pathogen Infection site TreatmentErysipelas Group A Streptococci (GAS)Usually appears first on face; often preceded by GAS sorethroat; Can enter blood stream causing sepsisB-lactam antibiotics: CephalosporinNecrotizing Fasciites “Flesh eating disease”Invasive strains of GAS; Super antigen Immune dysfunctionBegins with simple break of the skin, once established can destroy tissues rapidlydue to Exotoxin A production. Associated with streptococcal Toxic Shock Syndrome (Strep. TSS)Surgical debridement (cutting away uninfected skin) or amputation. Mortalityrate is 40%Pseudomonas Skin Infections- Aerobic gram-negative rod common to soil and water- Diverse metabolic capabilities: can grow on varied and unusual organic compounds sources- Resistant to many antibiotics and disinfectants- Serious problem in burn patients - Multiple toxins and pyocyanin contribute to burn infection pathogenesis- Multiple drug resistance exacerbates illness- Sepsis can be life threateningAcne- Most common skin infection: 17 million people in US and 85% of teens- Comedones- Accutane reduces sebum production, clears acne in most casesDisease Pathogen Infection site TreatmentPseudomonas dermatitisPseudomonas aeruginosaSelf-limiting skin rash acquired from swimming pools and hot tubs. Also affects burn victimsNo treatment discussed during lectureOtitis Externa Pseudomonas External ear canal No treatment(Swimmer’s Ear) aeruginosa discussed Inflammatory Acne Propionibacterium AcnesDead skin cells mix with sebum in a hair follicle; has nutritionalrequirement for glycerol found in sebumAccutane reduces sebum productionCommedonal Acne Comedones Shedding skin cells mixed with sebum clog folliclesN/aNodular (cystic) acne N/a Nodules/cysts; inflamed regions filledwith pus deep within tissues; can lead to scarringN/aViral Diseases of the SkinDisease Pathogen Infection Site TreatmentWarts Papillomavirus;>50 types knownBenign skin growths; some skinand cervical cancers associatedwith strains of papilloma virusCryotherapySmallpox Smallpox Variola Virus (orthopoxvirus)Disease transmitted via the respiratory route causes lesions on the skin; result in severe scarring (face, head, neck)Smallpox vaccine, disease has basically been eradicated;Variola major = mortality rate >20%,Variola minor ~1%; death from respiratory failureChickenpox (Varicella)Varicella-Zoster(Human Herpes viruse- 3)Skin rash characterized by vesicles that fill with pus and forms scabs. Latent virus; enters peripheral nervous system following primary disease; acquired by inhalationor deposition in nasopharynx; virus localizes in skin in about 2weeksChickenpox vaccineShingles Herpes-Zoster Skin rash caused by latent chicken pox virus that moves along the peripheral nerves to Anti-viral drugs; Acyclovir, valacyclovir, and famiciclovir reduce severity and shortenthe cutaneous sensory nerves of the skin causing severe pain;midsection usually affectedduration of shingles episodesHerpes Simplex VirusHerpes SimplexVirus; HSV-1 and HSV-2HSV-1: transmitted by oral and respiratory routes; occurs in infancy (90%); subclinical, can cause cold sores and fever blisters; remains latent in trigeminal nerve ganglia until reactivation, travels down nerve axon to site of eruptionHSV-2: similar to HSV-1, transmitted through sexual contactHerpes encephalitis: rare, can be caused by HSV-1 or HSV-2Acyclovir; fatality rate with HSV-2 is 70% if untreatedMeasles RubeolaMeasles Virus; member of Paramyxoviridae; Extremely contagiousSpread through droplet contact from nose, mouth, or throat; rash begins on face andspreads to trunk and extremities. Can cause rare neurological complication of subacutesclerosingpanencephalitisMeasles vaccine (MMR) has all but eliminated the disease except in infants under 1; subacutesclerosingpanencephalitis: death within daysMeasles Rubella “German Measles”Rubella Virus Causes