Microorganisms and Disease How does the human body and various microorganisms interact in terms of disease?

Virulence of Organisms 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: 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” blood: viremia; bacteremia

Readings question #2: Define septicemia and toxemia and include an example of each. What are the symptoms/characteristics for septicemia and toxemia?

Factors Influencing Virulence Readings question #3: Describe toxins, exotoxins, and endotoxins, and give an example of each. Capsules and Endospores

Transmission of Infections 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: What is a vector? What are biological and mechanical vectors? Give an example of each.

Resistance of the Host 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 Inflammation: pus Fever: degrees Phagocytosis: phagocyte ingests material

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 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 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