"SLE334 Medical Microbiology and Immunology, T2, 2017Topic 1: The Enemy – MicrobesThe Prions and host-parasite relationships(Mims’ Chapters 7 & 8)Lecture 5Friday 21 July 2017LT12 (X2.05), 10-11 am(date, time and venue different for Geelong students)Dr Sharon La [email protected] Medical Microbiology and Immunology, T2, 2017This lecture will cover……•? Prions•? Host-parasite relationship- the normal flora- symbiotic relationships- parasitism•? Evasion Strategies of microbes•? Lifestyle changes and infectiousdisease SLE334 Medical Microbiology and Immunology, T2, 2017Prions SLE334 Medical Microbiology and Immunology, T2, 2017Prions•? Unique infectious agents (<100 nm, filterable)•? Lack of nucleic acid genome•? Small, proteinaceous infectious particlessc •? Host-derived molecules (PrP )•? Can cross species boundaries•? Causes kuru and Creutzfeldt-Jakob diseases(CJD)- spongiform encephalopathies - pathology is characterized by large vacuolesin the CNS. •? Cannot be cultured in vitro•? Prion diseases difficult to diagnose•? Prion diseases are incurable SLE334 Medical Microbiology and Immunology, T2, 2017How Prions May Damage Cells•? infectious agent known to be ahost-derived glycoproteinSc (termed PrP , prion proteinscrapie)Sc •? PrP derived from a naturallyoccurring cellular prion proteinc (PrP ), expressedpredominantly on the surfaceof nerve cellsSc •? PrP is globular and enzymec resistant;PrP is linear andenzyme susceptible. Sc c •? association of PrP with PrPc results in conversion of PrPinto the abnormal formSLE334 Medical Microbiology and Immunology, T2, 2017Spread of Scrapie AgentsBetween Species*Infections transferred by scrapie-infected sheep materials present in foodstuff. •? transmission can occur between different species. •? most serious example is the transfer of prions from cattle infected with BSE tohumans through consumption of infected meat•? BSE arose from transfer of prions from sheep infected with scrapie to cattleSLE334 Medical Microbiology and Immunology, T2, 2017For some interesting History of Mad Cow (BSE), Scrapie, Kuru and otherhuman prion diseases, visit:http://www.stanford.edu/group/virus/prion/prion2.htmlBoy with Kuru•?sections of diseasedbrains, with thecharacteristic spongiformappearance withvacuoles (arrows).http://nobelprize.org/nobel_prizes/medicine/laureates/1997/illpres/brain.htmlhttp://www.weeklyecho.com/blog/cool.php?itemid=55By the 1950s, anthropologists and Australian governmentofficials reported that kuru was rampant in PNGThe infected group partook in acts of cannibalism as part offuneral ritualsThis behaviour later determined to be responsible for theepidemic transmission of the disease. The disease all but disappeared with the termination ofcannibalism in New Guinea.SLE334 Medical Microbiology and Immunology, T2, 2017Some interesting articles1. Prion disease can spread through air13 January 2011 by Debora MacKenziehttp://www.newscientist.com/article/dn19971-prion-disease-can-spread-through-air.html2. Aguzzi A, Zhu C (2012). Five Questions on Prion Diseases. PLoS Pathog 8(5):e1002651. doi:10.1371/journal.ppat.1002651http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1002651http://www.cdc.gov/prions/vcjd/news.html SLE334 Medical Microbiology and Immunology, T2, 2017Some interesting sites & videos•? http://www.youtube.com/watch v=pqhpVpafjmk&feature=related•? http://www.kuru-doco.com/•? http://www.kuru-doco.com/video.html?v=Teaser•? http://www.cdc.gov/prions/bse/index.html•? http://www.cdc.gov/prions/vcjd/news.html •? http://www.cdc.gov/prions/vcjd/news.htmlhttp://www.abc.net.au/news/2012-09-12/ mad-cow-disease-blood-test-a-step- closer/4256670SLE334 Medical Microbiology and Immunology, T2, 2017http://www.kuru-doco.com/ SLE334 Medical Microbiology and Immunology, T2, 2017http://www.kuru-doco.com/SLE334 Medical Microbiology and Immunology, T2, 2017Summary•? Unusual infectious agents (cause brain andmotor disturbances)•? Host-derived glycoproteins •? Lack nucleic acid genome•? Extremely resistant to disinfection procedures•? Transmission via ingestion of contaminatedtissues•? Causes kuru, Creutzfeldt-Jakob disease (CJD),variant CJD and bovine spongiformencephalopathy (BSE) SLE334 Medical Microbiology and Immunology, T2, 2017The Host-ParasiteRelationship SLE334 Medical Microbiology and Immunology, T2, 2017The Normal Flora•? A collection of species routinely found in the normalhealthy individual and which, in some cases, arenecessary for normal functioning of the human body.•? Majority is bacteria14 13 •? 10 bacteria associated with 10 cells in a body (mostlyin the large bowel)•? Viruses, fungi and protozoa form minor component•? Occur in parts of body exposed to external environment(i.e. skin, nose, mouth and intestinal/urinogenital tracts)•? Internal organs/tissues are sterileSLE334 Medical Microbiology and Immunology, T2, 2017Normal Flora•? Different regions of theskin support different flora•? Nose and mouth can beheavily colonized bybacteria•? respiratory tract isnormally quite sterile•? density of microorganismsincreases from thestomach to the largeintestine•? The urethra is lightlycolonized in both sexes,but the vagina supportsan extensive flora ofbacteria and fungi SLE334 Medical Microbiology and Immunology, T2, 2017The Normal Flora•? Acquired rapidly during and shortly after birth•? Changes continuously throughout life•? Different skin regions support different flora•? Both the nose and mouth heavily colonised by bacteria•? The most common infectious diseases in developedcountries is dental caries•? Pharynx and trachea carry their own normal flora•? Density of microorganisms increase from the stomach tothe large intestine•? Urethra lightly colonized in both sexes•? Vagina supports extensive bacteria and fungi floraSLE334 Medical Microbiology and Immunology, T2, 2017Normal Flora ofthe HumanGastrointestinalTract•? stomach normally harbors onlytransient organisms, its acidic pHproviding an effective barrier•? upper intestine is only lightly4 colonized (10 organisms/g), butpopulations increase in the ileum•? bacterial numbers very high in thelarge bowel, and many speciespresent•? vast majority are anaerobesSLE334 Medical Microbiology and Immunology, T2, 2017Benefits and Disadvantagesof Normal Flora•? Some species positively beneficial to the host•? Germ-free animals live longer (develop no caries)but immune system is less well-developed andvulnerable to introduced pathogens•? Disadvantages: potential for spread intopreviously sterile body parts (i.e. whenimmunosuppressed; AIDS) SLE334 Medical Microbiology and Immunology, T2, 2017Symbiotic Associations•? Symbiosis: all associations in which one specieslives in or on the body of another •? Categories of symbiotic association:commensalism, mutualism and parasitism•? Commensalism: one species of organism livesharmlessly in or on the body of larger species•? Mutualism: provide reciprocal benefits for bothorganisms involved•? Parasitism: benefits only the parasiteSLE334 Medical Microbiology and Immunology, T2, 2017Symbiotic Associations "