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Controlling Microbes. Microbes and Society. Different Ways of Controlling Microbes. Physical Chemical Antibiotics Immunological. Physical Control Methods. Sterilization- destruction of all forms of life Heat- causes denaturation (unfolding of proteins) Moist heat- steam, boiling water

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Controlling Microbes

Microbes and Society


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Different Ways of Controlling Microbes

  • Physical

  • Chemical

  • Antibiotics

  • Immunological


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Physical Control Methods

  • Sterilization- destruction of all forms of life

    • Heat- causes denaturation (unfolding of proteins)

      • Moist heat- steam, boiling water

      • Pressure heat- autoclave, as pressure raises, temperature raises and sterilization is better achieved


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Heat Continued

  • Pasteurization- a process of using hot water to destroy most of the heat-resistant microbial pathogens. Not a sterlization technique as it does not affect bacterial spores

  • Dry heat- hot air ovens. Takes a longer time but effective for powders, oily materials and dry instruments.


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Radiation

  • Radiation disrupts the nucleic acid components of a microbe

  • Ultraviolet (UV)

  • X ray

  • Gamma ray

  • Electron beams


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Other Physical Methods

  • Drying (desiccation)

  • Disrupt osmotic balance (salting)

  • Filtration (remember Giardia!)

  • Refrigeration-slows enzymatic activity, but doesn’t come near to sterilization


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Chemical

  • Disinfectants- chemicals used to “sterilize” inanimate objects

  • Antiseptics- chemicals used to “sterilize” surfaces of the body


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Alcohols and Aldehydes

  • Ethyl and isopropyl alcohol are two very important antiseptic/disinfectants

  • Aldehydes are effective but toxic. Need to be completely dried before material can be used.


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Halogens and Heavy Metals

  • Iodine and chlorine (halogens) are very good disinfectants.

  • Silver, mercury, copper and others are heavy metals that are good antiseptics/disinfectants. These are useful metals but are used with caution as they can be toxic.


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Detergents and Phenols

  • Detergents- wetting agents can lift microbes off of surfaces for better removal. They can also cause cell membranes to leak and cause cell death.

  • Phenols- good chemical disinfectants. However, trichlosan (the antibacterial chemical in soaps) has been implicated in resistance to such compounds due to overuse.


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Antibiotics

  • Penicillins-group of drugs that act primarily against Gram-positive bacteria and function during the synthesis of the bacterial cell wall.

  • Cephalosporins- a group of antibiotics also made from mold that also interfere with cell wall synthesis.

  • Aminoglycosides- (streptomycin is an example)- produced by a soil bacteria and function by inhibiting bacterial protein synthesis.


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Antibiotics Continued

  • Broad Spectrum- kills numerous types of microbes (gram Pos, gram neg, rickettsiae, chlamydiae, and fungi) Tetracycline is the most prescribed but may be overused (resistance). Some side effects may be yellowing of the teeth and stunted bones in children.

  • Others- erythromycin, vancomycin, rifampin and more.


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Control and Society

  • We have learned from history that science is not capable of eradicating infectious disease. Humans will always fight infections, and they can use all the weapons at hand to help control (physical, chemical and antibiotic).

  • However, the ultimate control relies in the immune system’s ability to overcome pathogenic microbes.


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Immunological

  • The defense of pathogens using the immune system (natural defenses).


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The Establishment of Disease

  • Respiratory Droplets

  • Dust (aerosols)

  • Contaminated food or water

  • Direct contact with contaminated object

  • Arthropod bites

  • Contact with animals

  • Injection with contaminated soil/object


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Types of Pathogens

  • Bacterial

  • Viral

  • Parasites

  • Fungi

  • Prions


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What is Immunity?

  • A complicated web of cells and chemical signals that work in concert to protect the body from pathogens and injury

  • Cells are educated to distinguish between “self” and “non-self”


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Two Branches of Immunity

  • Innate (Non-specific)

  • Adaptive


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Innate Responses

  • Physical/Chemical Barriers- skin, pH, mucous membranes, cilia, sweat glands, others

  • Microbiogical- Direct competition of good microbes over bad microbes

  • Cellular- Phagocytosis, Granulocytes and Inflammation


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Cells without Memory (innate)

  • Macrophages-very important cell of the immune system. An antigen presenting cell (APC), phagocytic cell, and recruiting cell in the inflammatory response

  • Neutrophils- phagocytic cell that is often the first line of defense. Short lived but effective.

  • Dendritic Cells- Professional APC

  • Mast Cells- tissue dwelling cell, often involved with allergies

  • Eosinophils- responsible for killing parasites, often involved with allergies/asthma

  • Basophils- similar to eosinophils

  • Natural Killer Cell (NK)- direct cell killing and/or recruiting cell



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Signs of Inflammation

  • Heat, Pain, Redness, Swelling (calor, dolor, rubor, tumor).

  • Cells involved- Macrophages, Neutrophils

  • Other substances involved- cytokines, complement


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Specific Resistance (Cells with Memory)

  • Terminology:

    • Antigens- chemical substances capable of stimulating the immune response (mostly proteins)

    • Antigenic determinant (epitope)- the small part of an antigen that the lymphocytes recognize in order to stimulate the specific response


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Cells with Memory

  • B lymphocytes (B Cells)- differentiate into antibody secreting plasma cells

  • T lymphocytes (T Cells)-

    • CD4 (T Helper Cells)- help with the inflammatory response and/or help B Cells make antibodies

    • CD8 (Cytotoxic T Cells)- directly kill virally infected cells


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Adaptive ResponseClonal Selection Theory

  • Random unique receptors confer specificity

  • Clones

  • Some clones become memory cells

  • Response gets better over time (more cells, faster response, better specificity)

  • Cells capable of recognizing “self” molecules are destroyed.


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Cell-Mediated Immunity

  • Macrophage (or other APC) processes and presents antigen on MHC class I

  • CD8 (or Cytotoxic T Cell) recognizes antigen being displayed on MHC

  • Clones

  • Some become effector cells (kills virally infected cells)

  • Some become memory cells for the next time


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Cell-Mediated ImmunityEffector Cells


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Antibody-Mediated Immunity(Humoral Immunity)

  • B Cell recognizes (binds to) antigen.

  • B Cell processes antigen and displays it on MHC class II

  • Meanwhile, a macrophage activates a T Cell which clones itself

  • T Cell activates B Cell by binding with the MHC displayed on B Cell surface

  • T Cell activates B Cell

  • Some B Cells become plasma cells and secrete antibodies while others become memory B Cells





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Antibody Isotype Functions

  • IgG- most abundant in blood/serum. Crosses the placenta. Found in extracellular fluids.

  • IgM-first antibody produced, excellent at activating complement (proteins used in immune reactions)

  • IgA-protects the mucosal surfaces, passed in breast milk

  • IgE-specific for parasitic infections, often seen in allergic reactions

  • IgD- receptor on B Cell surfaces


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Antibody Functions

  • Neutralization- neutralizes toxins so they can’t hurt cells

  • Opsonization- allows for more efficient phagocytosis of organisms

  • Agglutination- clumps non-soluble antigens

  • Precipitation-forms lattices of antibody and soluble antigens

  • Inhibition- keeps pathogens from binding to receptors and gaining access





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Immunity Gone WrongHypersensitivity Reactions

  • 4 Types of Hypersensitivity Reactions

    • Type I- allergies

    • Type II- Cytotoxic- antibodies to cell surface antigens (incompatible blood types or hemolytic disease of the newborn)

    • Type III- Immune complex hypersensitivity- accumulation of immune complexes in blood tissues (Systemic lupus erythematosus-SLE) or Rheumatoid arthritis

    • Type IV- Delayed or cellular hypersensitivity- T Cell mediated, takes 24-72 hours for effects. Poison ivy and other chemical/skin reactions




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