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HSS1100 Midterm: Midterm #1

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University of Ottawa
Health Sciences
Franco Pagotto

HSS 1100 E Midterm #1 Review Package Topic 1: General Principles of Microbiology  Immunology = study of our protection from foreign macromolecules or invading organisms and our responses to them  Different Classes of organisms: - Viruses / chlamydia (grow only in living cells) - Mycoplasma (grow on non-living media) - Bacteria (no separate nucleus; unicellular) - Parasites - Small (microscopic): 1-2 microns (1 mm = 1000 microns); proper name (not ”germs” ”bugs”)  Viruses - Nucleic acid (either RNA or DNA…never both) - Surrounded by protein shell (protein shell=capsid) - Attach, inject nucleic acid (penetration), highjack synthetic processes inside cells to make more viruses, package, get out while going is good..  Bacteria - Rigid cell wall to keep things in place - Genetic material: circular chromosome - No nucleus (nucleoid) - Both DNA and RNA - Binary fission - Some bacteria do not have a rigid cell wall and are more fragile (i.e. Mycoplasmas)  Eukaryotes - Unicellular and multicellular animals and plants - Genetic material is organized into a nucleus  Normal Bacterial Flora (good guys) - Resident V.S. Transient - GI-tract: colon is inhabited by anaerobes and coliforms - Skin: mostly coagulase negative staphylococci - Transient as a result of displacement of resident flora, injury or trauma, human behaviors - No bacteria: central nervous system, respiratory system, blood, sub-cleaning system - Function: ·protection from invasive (bad) bacteria ·metabolism (vitamin K), immune stimulation  Protections from bad guys - Mechanical barriers ·skin, saliva, mucous, tears, hairs, etc. - Other helpers include ·antibodies (humoural immunity) ·complement (a complex system of plasma proteins that work together to resist bacterial infection) ·immune cells (T-cells, NK cells, macrophages) ·immune system (cell mediated; humoural; endo/exo-toxin production)  How do the bad guys get in - Adherence: ·Ligands (usually small molecules) are present on the surface of the bacteria, able to bind to specific receptors on the mammalian cell surface. ·Adhesion of the bacteria to the host tissue is a prerequisite for the initiation of an infectious process. - Toxin production (destroys some of our defenses) - Opportunism - Compromised host: ·may be deficient in some of the antimicrobial defences the body has ·due to a disease process, medical or surgical procedures, administration of medication - Metastatic Spread转移扩散 (aemia = blood) ·bacteraemia: bacteria in blood ·septicaemia: blood poisonin败血症 Topic 2: Pathogenesis of infectious disease and the immune response  Microbial disease - Interaction between microorganisms and the host (us) is continuous battle - need to enter-live-multiply - In order to enter, they need to colonize (establish and multiply) in/on body; clinical infection (disease, e.g. fever) can result when damage occurs to host [contamination= deposition without multiplication] - Clinical disease = easy to recognize - Sub-clinical infection = hard to diagnose (no symptoms)  Measurement of how dangerous a bacteria/virus/parasite is - Pathogenicity = ability to produce disease - Virulence = relative capacity to cause damage (i.e., the degree of pathogenicity) - Opportunistic = do not normally cause disease but can do so when defense mechanism(s) breached or compromised  Pathogenesis of infectious diseases - A pathogenic microorganism enters your body, two things happen: nd 1. Microorganism (invader) tries to multiply / invade and cause disease (2 event) 2. Host tries to prevent (1 event) - Whether the invader wins or not is dependent on several factors:  Transmission: - Routes of entry: inhalation, ingestion, break in protective barrier, direct deposit - pathogenicity: the capacity to cause disease - invasiveness: ·ability to overcome host defences and multiply ·adherence - persistence - avoidance of immune system - toxigenicity: ability to make toxins  The means by bacteria adhere to us - A bacteria needs to adhere, evade and invade the host - Tools used to achieve these huge objectives: ·surface structures (pili, fimbriae): adhere to specific receptors present on surfaces ·capsules: usually polysaccharides, protect the microorganisms against leucocytes ·enzymes: not toxic, may contribute towards the virulence of the pathogen  Toxinogenicity - Toxins are substances (usually proteins) secreted by bacteria with the hope to cause damage - Two classes: ·Exotoxins: - excreted by living bacterial cells - specific affinities - thermolabile (sensitive to heat) - potent (active in very small concentrations) ·Endotoxins: - liberated only when cell wall disintegrates - less specific, but may causes fever, malaise, shock - thermostable (resistant to heat) - less potent than exotoxins Topic 3: Immunity to Infection (Body Defenses)  Immunity (Body’s ability to resist infection) = the protection against infectious disease conferred either by the immune response generated by immunization or previous infection or by other nonimmunologic factors.  ·Two types of immunity: - Non-specific (innate) - Specific (adaptive, acquired)  Innate/nonspecific immunity ·Skin: - Mechanical barrier; - Acid: sebaceous secretions and sweat contain unsaturated fatty acids(bactericidal) ·Mucous membranes - mechanical barrier; - Cilia in respiratory tract - Lysozymes (antibacterial substance, tears) - pH (acid pH in vagina, gastric juice, urine) • Iron-binding proteins: - Some bacteria require Fe for growth - Transferrin, lactoferrin • Phagocytosis 吞噬作用 - PMN (polymorphonuclear) WBC, monocytes and macrophages • Complement  Specific/Acquired/Adaptive Immunity - Mechanisms aimed at particular infecting organisms - Humoral V.S. Cell-Mediated(CMI)  Differences between innate & adaptive immunity: - Innate: protects against ANY invader, does not discriminate - Adaptive: directed against one particular type of invader, dependent on past exposure  Humoral Immunity - Specific circulating antibodies in body fluids - Antibodies: - protein that binds specifically to a substance (its antigen) - immunoglobulins (igs) - Produced by B-lymphocytes (B-cells) upon stimulation from antigen presenting T-cells - Antibody production is regulated by T-helper and T-suppressor cells. - Recognize toxins, capsules, some viral proteins - Antigen: - the chemical components which stimulate the production of antibodies - must be recognized by foreign body (non-self) - Protein, glycoprotein, lipoprotein, polysaccharide - “antigenic” molecules in bacterial cells: capsular substance, flagella, cell wall, etc. - In viruses: polypeptide antigens - Immunoglobulins (igs) a.k.a Antibody: - antibody is an immunoglobulin produced in response to stimulation by an antigen and reacting specifically with it - ability to distinguish foreign macro-molecules (NON-SELF) from “normal” body constituents (SELF) - Constant & variable region (Variable region is responsible for antigen recognition) Y - 5 classes of Igs ·IgG : - Host defense - Crosses placenta and protects newborn ·IgD : role is unknown ·IgA : - Host defense - Found in secretions (tears, saliva, milk, respiratory, GI and genito-urinary tract) - Dimer(2 units joined together) • IgM : - Host defense - Early immune response - Pentamer (5 units joined together) ·IgE : - Hypersensitivity (allergies) - Defends against parasites  Primary 1 and Secondary 2 immune response  Primary 1º Response - Ab production triggered on first antigen introduction - Latent period of several days - Circulating antibody detectable after 5-10 days - Antibody in serum is maximum at ~21 days, then drops to low levels  Secondary 2º Response - Basis for Immunizations - Occurs when Ab is introduced 2nd, 3rd,4th…time - delay, rapid Ab increase (2-3 days), slow decrease - Booster injections to maximize Ab levels  Antibody Detection
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