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Defense Against Infectious Diseases

Defense Against Infectious Diseases. 6.3. Pathogens · An organism or virus that causes a disease ·Viruses, bacteria, fungi, protozoa, flatworms, and roundworms can all be pathogens. Examples include: ·Viruses – Rhinovirus (causes the common cold), HIV, HCB (Hepatitis B virus)

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Defense Against Infectious Diseases

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  1. Defense Against Infectious Diseases 6.3

  2. Pathogens ·An organism or virus that causes a disease ·Viruses, bacteria, fungi, protozoa, flatworms, and roundworms can all be pathogens

  3. Examples include: ·Viruses – Rhinovirus (causes the common cold), HIV, HCB (Hepatitis B virus) ·Bacteria – Staphylococcus (causes strep throat), Vibrio Cholerae (causes cholera), Myobacterium tuberculosis (causes TB) ·Fungi – Candida (yeast infections), Trichophyton (fungus that causes ringworm)

  4. Methods of transmission ·Cuts in the skin ·Mouth, Nose, and Eyes · Vectors (animals that transmit disease) ·Sexual Transmission ·IV Drug Use ·Blood Transfusions ·Food and Water

  5. Antibiotics ·Work on bacteria, not viruses ·Antibiotics block specific metabolic pathways found in bacteria, but not in eukaryotic cells (such as our own) - Examples: RNA/DNA replication, transcription, translation, 70S ribosome function and cell wall formation ·Since viruses do not metabolize on their own (they use our cell’s metabolic machinery) they are not effected by the antibiotics

  6. Antibiotics: Types ·_____-static: (bacteriostatic, fungistatic) stop further growth but don’t kill existing microbes. Buys time for immune system to catch up and target microbes. ·_____-cidal: (bacteriocidal, fungicidal) kills microbes

  7. Antibiotic resistance ·Some bacteria develop a gene mutation that makes them naturally resistant to antibiotics ·Resistance can be transferred from strain to strain and sometimes from species to species ·Bacteria that have a resistance mutation survive when antibiotics are used and other bacterium die

  8. ·Resistant bacteria pass on their genes for resistance to offspring ·Proportion of resistant bacteria increases in each generation ·This is an excellent example of natural selection and evolution

  9. Barriers to infections ·First line of defense: prevent pathogens from entering the blood stream - Skin > a tough, impenetrable physical barrier > has a lower pH which make it inhospitable for many bacteria > Sweat has lysozymes (special enzymes) that destroy bacteria

  10. - Mucous membranes > Traps pathogens because it is sticky > Cilia in the throat sweep up bacteria and allow them to be swallowed and then destroyed by acid in the stomach > Contains phagocytes (white blood cells that ingest and destroy pathogens)

  11. nonspecific antigen specific

  12. Cellular Defense ·Second line of defense is the non-specific immune system - a host of quick, non-specific methods of killing microbes that have entered the body. - Phagocytes: large, irregularly- shaped leukocyte cells that remove bacteria, viruses, cellular debris and dust particles.

  13. > Are constantly changing shape, and they flow over pathogens, surrounding and ingesting them through the process of phagocytosis to form a phagosome > Enzymes within the lysosome of the phagosome break down the pathogen > Different phagocyte cells work in different locations: *neutrophils circulate in the blood *macrophages are found in lymph, tissue fluid, lungs and other spaces, where they kill microbes before they enter the blood

  14. Antigen and Antibodies

  15. Antigen and Antibodies ·Antigens - Large molecules on the outer surface of cells - All living cells as well as viruses have antigens - All cells in one organism will have the same type of antigen (which is genetically controlled) - Therefore, the antigen acts as identification marker for cells - If a pathogen enters the body the immune system will detect the foreign antigen and begin to attack

  16. ·Antibodies (also called immunoglobulin) - Proteins that bind to the specific antigen on a pathogen to help to destroy it - Each has a variable region that is antigen specific (similar to enzyme specificity)

  17. Antibody production ·Many types of b-cells exist ·Each type recognizes one specific antigen and responds by dividing to form a clone ·This clone then secretes numerous copies of a specific antibody against the antigen ·Cloning and antibody production is always initiated by the binding of a t-cell (another type of white blood cell) to the b-cell

  18. HIV and Aids ·HIV stands for Human Immunodeficiency Virus >can lead to AIDS (acquired immunodificiency syndrome) ·It survives by invading and killing T-Cells ·When enough T-cells have been destroyed, the immune system begins to fail and AIDS has begun Treatment Research

  19. HIV and AIDS ·Aids patients do not die from the virus itself, but rather from "opportunistic infections" >the diseases that take hold of the body in the absence of a proper immune system

  20. HIV transmission mediums

  21. HIV Testing ·find a clinichttp://hivtest.cdc.gov/ ·home tests Who should get tested? ·everyone between the ages of 13 and 64 at least once as part of routine health care. ·Testing once a year (or more) is recommended for people at higher risk of HIV infection

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