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Microorganisms and Disease How does the human body and various microorganisms interact in terms of disease? Virulence of Organisms (page 315) • virulence: “relative power of an organism to produce disease” • resistance • host • pathogen • contamination: “the act of introducing disease germs or infectious material into an area or substance” Virulence (cont’d) • true pathogen: “an organism that due to its virulence is able to produce disease: • attenuation: “dilution or weakening of virulence of a microorganism, reducing or abolishing pathogenicity” • pathogenicity: “the state of producing or being able to produce pathological changes and disease” Virulence (cont’d) • indigenous flora: “synonymous with normal flora, indicates the microbial population that lives with the host in a healthy condition” • opportunists: “an organism that exists as part of the normal flora but may become pathogenic under certain conditions” • drug-fast: “resistant, as in bacteria, to the action of a drug or drugs” Readings Question #1 Page 316 Define local, focal, and general infections, and give an example of each. Infections (cont’d) • primary: “the first infection that a host has after a period of health” • secondary: “infection caused by a different organism than the one causing the primary infection • mixed: “infection caused by two or more organisms” (Fig. 24-2 page 317) • blood: viremia; bacteremia Readings Question #2 Page 316 Define septicemia and toxemia and include an example of each. What are the symptoms/characteristics for septicemia and toxemia? Color Plate 38 Factors Influencing Virulence • Readings question #3: Page 319 Describe toxins, exotoxins, and endotoxins, and give an example of each. Capsules and Endospores Transmission of Infections (Page 323) • Direct: viral respiratory disease, staphylococcal infections, hepatitis A, measles, scarlet fever, STDs, AIDS, infectious mononucleosis - hand washing, gloves etc. • Indirect: Readings question #4: Describe the four primary mechanisms of indirect contact. Include examples with each mechanism. What are fomites? Readings Question #5 • Page 326 • What is a vector? What are biological and mechanical vectors? Give an example of each. Resistance of the Host • Page 329 • mechanical defenses • physiological defenses • chemical defenses Mechanical Defenses • Skin: epithelium (epidermis), sebaceous glands, dryness, “necrobiosis” • Eyes: lacrimal apparatus • Saliva: cleansing action • Respiratory Tract: mucus, ciliated epithelium • Urinary Tract: flushing action Physiological Defenses • Page 331 • Inflammation: pus • Fever: 102-104 degrees • Phagocytosis: phagocyte ingests material - Page 332 Figure 24-8 Chemical Defenses • Lysozome: enzyme that breaks down cell walls of gram-positive bacteria and some gram-negative bacteria • Sebum: sebaceous glands, oily substance, protective film, lowers skin pH • Gastric Juice: HCl, enzymes, mucus, acidic • Interferon: eukaryotic cells, surface receptors Immunology • Page 333 • Latin immunis “to exempt” • Why is it that some people tend to be sick more often than others? • Why can two people eat the same infected chicken, and only one person contracts food poisening? • children, elderly, immunocompromised Antigens • “a foreign substance that stimulates the formation of antibodies that react specifically with it” • substance that provoke a specific response • Antibodies: “glycoprotein substance developed by the body in response to, and interacting specifically, with an antigen. Also known as immunoglobulin.” Antigen-Antibody Reactions • 1) destroy pathogens by neutralizing the toxins the pathogen produces • 2) coat the pathogen with a substance that attracts phagocytes by forming a substance that clumps the antigens together • 3) prevent the pathogen from adhering to the body’s cells Types of Immunity • Page 334 • Natural (Innate) • Acquired: Naturally Acquired – active, passive Artificially Acquired - active: vaccines - passive: antibodies immune serums Hypersensitivity (Allergy) • “an acquired, abnormal immune response to a substance (allergen) that does not normally cause a reaction” • Immediate: 2 – 30 minutes – systemic (shock, breathing difficulties) – Localized (hay fever, asthma, hives) • Delayed: 1-2 days – TB skin test, contact dermatitis