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What is Salvarsan?
- First documented chemical used as an antimicrobial.
- Discovered by Paul Erlich in treatment of syphillis
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Who discovered penicillin and how?
- Alexander Flemming
- Accidentlly while working with staphyloccoccus.
- Noticed there were no colonies growing near a mold contaminant...thought the colonies were "melting."
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When and what was the first antibiotic tested on humans?
- WWII
- Treatment of wounded soldiers for staphylococcus aureus infections
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What is Penicillin G?
The first alteration of penicillin, broadened its spectrum
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What is MRSA?
Methicillin Resistant Staphyloccocus Aureus
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Where do most modern antibiotics come from?
Organisms living in the soil
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How are commerical antibiotics produced?
- Strain inoculated into broth medium
- Incubated until maximum ideal concetration is reached
- Drug extracted from medium
- Extensively purified
Sometimes altered to achieve new characteristics, ie capsules, liquid.
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What is theapeutic index?
- Lowest does toxic to patient divided by dose typically used for treatment.
- High therapeutic index = less toxic to patient
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What are the 2 antimicrobial actions?
- Bacteriostatic - inhibits further bacterial growth, but doesn't kill the bacteria
- Bacteriocidal - kills bacteria
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What are the 2 spectrums of activity for antimicrobials?
- Narrow Spectrum - Works on narrow range of organisms only. EX - Gram positive OR negative
- Broad Spectrum - Works on broad range of organisms; causes disruption of normal flora
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What is a drugs half-life?
- Time it takes for the body to eliminate one half the original dose in serum
- Dictates frequency of dosage
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Synergistic, Antagonistic, and Additive effects of drugs on each other:
- Synergistic - One drug enhances performance of another
- Antagonistic - One drug interferes with effect of another
- Additive - When added drug does not effect another drug
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What are the adverse effects of antimicrobial drugs?
- Allergic Reactions - often life threatening
- Toxic Effects - Aplastic anemia, body cannot make R or WBC's.
- Supression of normal flora - When normal flora is diminished, other organisms have an opportunity to move in
- Antimicrobial resistance - Microogranisms can come immune to antibiotics
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What are the "Mechanisms of Action" of antimicrobial drugs?
- Inhibition of cell wall synthesis (do not effect humans or other eurkaryotes)
- Inhibition of protien synthesis (ribosomes)
- Inhibition of nucleic acid synthesis (nucleus)
- Inhibition of metabolic pathways (mitochondria)
- Interference with cell membrane integrity
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What are natural penicillins?
- Narrow spectrum
- Effective against gram + and - cocci
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What are broad spectrum penicillins?
- Penicillins that has a modified side chain
- Effective against gram + and -
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How does vancomycin work?
- Inhibits formation of glycan chain
- Must be given intravenously due to poor absorption in digestive tract
- Important in treating infections caused by penicillin resistant gram + organisms
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What are cephalosporins?
Broad range of antibiotics that are resistant to beta lactams
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What is Bacitracin?
- Common ingredient in non-prescription first aid ointments
- Highly toxic
- Can only use topically
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Which antibiotics inhibit protien synthesis?
- Aminoglycosides
- Tetracyclins
- Streptogramins
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How does streptomycin work?
Causes misreading of mRNA
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How do tetracyclins work?
- Blocks attachment of tRNA to ribosome
- Causes discoloration of teeth if taken as a young child
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How does ciprofloxacin (a fluoroquinolones) work?
Inhibits action of DNA enzyme
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What does inhibiting the metabolic pathway do?
Inhibit the production of folic acid
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What is polymixin B?
- Common ingredient in first aid ointments
- Can bind to eukaryotic cells (humans)
- Limited to topical use
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What is MIC?
- Minimum Inhibitory Concentration
- Smallest effective dose
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How is MIC determined?
- By examining strains ability to grow in broth containing different concentrations of test drug
- Serial Dilution - Test tubes inpregnanted
- Disc Diffusion Method - Discs impregnated with antibiotic and placed on plate
- E-test - Strips impregnated with antibiotic
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What are the 2 types of "Acquisition of Resistance?"
- Spontaneous Mutation - Natural alteration of existing genes, relatively rare
- Acquisition of New Genes - Occurs most commonly by conjugation
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What are some emerging examples of antimicrobial resistance?
- Enterococci - some strains now resistant to vancomycin, Termed - "Vancomycin Resistant Enterococcus" or "VRE"
- MRSA - strain of staphylococcus arueus now resistant to Methicillin
- Streptococcus pneumoniae - some strains have gained resistance to penicillin
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What is the mechanism of action for antiviral drugs?
Viral uncoating - prevents severity and duration of disease
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