mrs. stewart medical interventions central magnet school
TRANSCRIPT
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Bacteria and Antibiotics
Mrs. StewartMedical InterventionsCentral Magnet School
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2 Classes of Bacteria
GRAM (-)
Thin layer of peptidoglycan
Lipopolysaccharides (endotoxins)
Stain red
GRAM (+)
Thick layer of peptidoglycan
Stain blueish - purple
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What’s the difference?
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Gram Stain
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)
Bacteria are stained with two stains:1.Crystal Violet stain (blue/purple)2.Fuchsin counterstain (red)
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Think – Pair – Share
What cellular components do some bacterial cells have that make them powerful pathogens? Explain.
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Neisseria Meningitidis
GRAM -
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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
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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 = penicillium notatum
•Later named: penicillin
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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
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Penicillin
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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)
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Which antibiotic is prescribed?
Depends on the bacteria
Gram +OR Gram -
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How Do Antibiotics Work?
Bactericidal – Kills the bacteria
Bacteriostatic – inhibits growth & reproduction
* The body’s natural defenses can usually take it from there
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Classes of antibiotics
Beta – Lactam Fluoroquinolones Tetracyclines Sulfanomides
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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
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Think – Pair – Share
Why are penicillins often more effective against gram positive than gram negative bacteria?
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Fluoroquinolones
Inhibit topoisomerase enzymes which prohibit DNA replication and protein synthesis
Broad spectrum – effective against + and -
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Tetracyclines
Bind the 30s ribosomal subunit, blocking the attachment of tRNA, thereby inhibiting protein synthesis
Broad spectrum – effective against + and -
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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
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Think – Pair – Share
Why is it important to understand the structure of a bacterial cell when developing an antibiotic?
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Think – Pair – Share
What class of antibiotics would you prescribe for Sue? Explain.
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When are antibiotics prescribed?
Bacterial infections only
Antibiotics target bacteria and a few parasites.
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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
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What type of infection is it?
Antibiotics are not effective against viruses.
Most colds and sore throats are caused by viruses
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Think – Pair – Share
How do antibiotics function without harming the surrounding human cells?
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Should we take antibiotics if we are
unsure what the pathogen is? NO
That leads to antibiotic resistance due to overuse
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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
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Examples:
Ear Infections
MRSA
TB – Tuberculosis
Strep throat