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Bacteria and Antibiotics

Mrs. Stewart Medical Interventions Central Magnet School. Bacteria and Antibiotics. 2 Classes of Bacteria. Gram (-) . Gram (+). Thick layer of peptidoglycan Stain blueish - purple. Thin layer of peptidoglycan Lipopolysaccharides ( endotoxins ) Stain red. What’s the difference?.

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Bacteria and Antibiotics

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  1. Mrs. Stewart Medical Interventions Central Magnet School Bacteria and Antibiotics

  2. 2 Classes of Bacteria Gram (-) Gram (+) Thick layer of peptidoglycan Stain blueish - purple • Thin layer of peptidoglycan • Lipopolysaccharides (endotoxins) • Stain red

  3. What’s the difference?

  4. Gram Stain Bacteria are stained with two stains: Crystal Violet stain (blue/purple) Fuchsincounterstain (red) Gram + • Blueish-purple • Peptidoglycan layer absorbs the crystal violet stain Gram – • Red • LPS cell wall prohibits peptidoglycan layer from absorbing crystal violet stain (absorbs counter stain)

  5. Think – Pair – Share • What cellular components do some bacterial cells have that make them powerful pathogens? Explain.

  6. NeisseriaMeningitidis GRAM -

  7. How do we treat bacterial infections? • Antibiotics are drugs used to treat infections caused by bacteria. • Antibiotic - A substance produced by or derived from a microorganism and able in dilute solution to inhibit or kill another microorganism

  8. History of Antibiotics 1928- Alexander Fleming Accidentally discovered penicillin Left lab untidy for a month and went on vacation Came back and found a fungus growing in one of his bacterial cultures. Fungus was inhibiting the bacteria. Fungus = penicilliumnotatum Later named: penicillin

  9. Gangrene and Sepsis - WWI • Gangrene – wound infections that lead to many amputations or sepsis • Sepsis – bacterial infection in blood stream – leads to organ system failures

  10. Penicillin

  11. Where Do Antibiotics Come From? • The early antibiotics = natural products of other microorganisms (fungi or other bacteria) • Now= created synthetically (chemically altering existing natural products)

  12. Which antibiotic is prescribed? • Depends on the bacteria • Gram + OR • Gram -

  13. How Do Antibiotics Work? • Bactericidal – Kills the bacteria • Bacteriostatic – inhibits growth & reproduction * The body’s natural defenses can usually take it from there

  14. Classes of antibiotics • Beta – Lactam • Fluoroquinolones • Tetracyclines • Sulfanomides

  15. Beta – Lactam • Disrupt the synthesis of peptidoglycan thereby inhibiting cell wall synthesis & damaging cell wall integrity • Broad spectrum (can work against + or -) • Bactericidal • Example: Penicillins

  16. Think – Pair – Share • Why are penicillins often more effective against gram positive than gram negative bacteria?

  17. Fluoroquinolones • Inhibit topoisomerase enzymes which prohibit DNA replication and protein synthesis • Broad spectrum – effective against + and -

  18. Tetracyclines • Bind the 30s ribosomal subunit, blocking the attachment of tRNA, thereby inhibiting protein synthesis • Broad spectrum – effective against + and -

  19. Sulfa (sulfonamides) • 1st class of antibiotics ever used • Structurally similar to PABA – a substance that the bacteria use to synthesize folate (folic acid) • Inhibits the synthesis of folic acid (Folate) • folate is necessary for DNA synthesis • No DNA synthesis (replication) = No cell division

  20. Think – Pair – Share • Why is it important to understand the structure of a bacterial cell when developing an antibiotic?

  21. Think – Pair – Share • What class of antibiotics would you prescribe for Sue? Explain.

  22. When are antibiotics prescribed? • Bacterial infections only • Antibiotics target bacteria and a few parasites.

  23. Why don’t antibiotics work on viruses? • They do not share the same structures • Viruses consist of a hereditary material (DNA or RNA) surrounded by a protein coat or fatty envelope. • They do not have any organelles – they hijack host cells to produce more DNA/RNA or proteins

  24. What type of infection is it? Antibiotics are not effective against viruses. Most colds and sore throats are caused by viruses

  25. Think – Pair – Share • How do antibiotics function without harming the surrounding human cells?

  26. Should we take antibiotics if we are unsure what the pathogen is? • NO • That leads to antibiotic resistance due to overuse

  27. How does overuse lead to resistance? • There are more bacterial cells in/on your body than there are human cells • Antibiotics will target all susceptible bacteria – not just the spot of infection • All bacteria living within your body will either die (susceptible) or will live (resistant) • Survival of the fittest

  28. Examples: • Ear Infections • MRSA • TB – Tuberculosis • Strep throat

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