Term
| antimicrobial drugs and antibiotics |
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Definition
-organic compounds that destroy or inhibit microorganisms growth
-natural antibiotics of fermentation pathway in spore forming bacteria and fungi |
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Term
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Definition
| natural antibiotics modified in the lab |
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Term
| why antibiotics against prokaryotes are easier to find |
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Definition
| -human and prokaryotic cells differ (cell wall, metabolism) |
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Term
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Definition
| -agent that is generally effective against a variety of G+ and G- bacteria |
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Term
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Definition
| only works against just G+, G-, or only a few bacteria |
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Term
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Definition
-selective toxicity
-kills the pathogen
-does not interfere with normal host defense mechanisms
-host should not become hyper sensitive or allergic
-host should not destroy, excrete, or neutralize the drug too rapidly
-should have a broad spectrum
-should not elicit antimicrobial resistance |
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Term
| mode of action of antibiotics (5) |
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Definition
-inhibit cell wall
-inhibit protein synthesis
-inhibit nucleic acid replication and transcription
-injury plasma membrane
-inhibit synthesis of essential metabolites |
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Term
| mode of action of antibiotics (5) |
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Definition
-inhibit cell wall
-inhibit protein synthesis
-inhibit nucleic acid replication and transcription
-injury plasma membrane
-inhibit synthesis of essential metabolites |
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Term
| inhibition of cell wall synthesis |
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Definition
-by blocking crosslinking of peptidoglycan strands
-inhibit transport of peptidoglycan subunits to the cell wall
-inhibit elongation of peptidoglycan strands |
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Term
| blocking the crosslinking of peptidoglycan strands |
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Definition
-results in osmotic lysis
-ex. penicillins and cephalosporins bind to transpeptidase enzymes responsible for resealing the cell wall as new peptidoglycan are added during bacterial growth |
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Term
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Definition
-Methicillin resistant Staphylococcus aureus
-due to the presence of beta lactamase which in activates penicillin
-methicillin is semi synthetic and resistant to the action of beta lactamase
-staphylococcus aureus became resistant to methicillin (and most antibiotics) |
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Term
| inhibition of transport of peptidoglycan subunits to cell wall |
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Definition
-no building blocks are available for peptidoglycan synthesis
-ex. Bacitracin- prevents monomers from being transported across cell membrane
-produced by strain of Bacillus subtilis
-main ingredient in Neosporin |
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Term
| inhibition of elongation of peptidoglycan |
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Definition
-ex. vancomycin
-binds to peptides of the peptidoglycan monomers and block formation of glycosidic and peptide bonds by transglycosidase and transpeptidase eznymes
-results in osmotic lysis |
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Term
| inhibition of protein synthesis |
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Definition
-inhibit formation of peptide bond
-change shape of 30S portion (mRNA reads incorrectly)
-interfere with attachment of tRNA to mRNA-ribosome complex |
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Term
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Definition
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Term
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Definition
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Term
| inhibition of nucleic acid synthsis |
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Definition
-ex. Rifamptin
-blocks transcription by inhibiting RNA polymerase |
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Term
| injury to plasma membrane |
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Definition
-Polymyxin B bind to negatively charged site in LPS
-fatty acid portion dissolves in hydrophobic region and disrupts membrane integrity
-amphotericin B is antifungal
-associates with ergosterol (main component of membrane)
-forms a channel that leaks potassium and causes death |
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Term
| inhibition of essential metabolite synthesis |
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Definition
-Sulfonamides
-block enzymes required for synthesis of tetrahydrofolic acid a cofactor needed to make nucleotide bases |
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Term
| Kirby Bauer method(disk diffusion) |
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Definition
-tests for antibiotic sensitivity
-solid culture medium inoculated with test organism
-filter paper with known concentrations of antibiotics are placed on the solid medium
-during incubation antibiotics diffuse into agar
-a zone of inhibition indicates sensitivity
-compared to standard table
-drug solubility varies |
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Term
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Definition
-same principle as Kirby Bauer
-uses a plastic strip with a predefined gradient of antibiotic concentration
-results read directly on the strip where zone of inhibition intersects
-allows to estimate minimal inhibitory concentration |
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Term
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Definition
-determines whether a drug is bactericidal not just bacteriostatic
-decreasing concentrations are added to a series of broths
-test organisms is added
-the lowest concentration does not allow growth (MIC)
-wells that do not show growth are cultured free of the drug
-if the drug was not bactericidal, growth will occur
-minimal bactericidal concentration is determined |
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Term
| mechanism of resistance to antibiotics (4) |
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Definition
-blocking entry
-inactivating enzymes
-alteration of target molecule
-efflux of antibiotic |
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