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21 Cards in this Set
- Front
- Back
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4 Main mechanisms of Antibiotic Resistance |
1) Alter or destroy antibiotic (using enzymes) - B-lactamase 2)Modify Antibiotic Target (DNA mutation or protein change) - methylate bacterial ribosome (Erythromycin) - amino acid substitutions in bacterial DNA gyrase (quinolone) - alter bacterial Penicillin Binding Protein (beta lactams) - phosphorylate, adenylate, or acetylate the target (aminoglycoside) 3) Exclude antibiotic from cell (pump it back out or don't let it in) - efflex pumps in bacterial membrane (tetracycline) - decrease permeability of porins in bacterial membrane (aminoglycoside) 4) Alter metabolic pathway (take other route) - reduce or eliminate need for precursors for folic acid pathway (sulfonamide) |
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What are the 5 main bacterial cell targets for antibiotics? |
1) DNA Gyrase 2) Ribosome 3) Cell Wall 4) Protein synthesis 5) Cell membrane |
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What are the major antibiotic classes (14) |
1)B-lactam 2) Cephalosporin 3) Carbapenem 4) Glycopeptide 5) Cyclic Polypeptide 6) Polyketide 7) Phenicol 8) Aminoglycoside 9) Macrolide/Lincosamides Streptogramin 10) Quinolone 11) Rifamycin 12) Sulfonamide 13) Nitroimidazole 14) Polypeptide |
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What is the target of B-lactams? |
Target: Cell Wall Spectrum: Narrow to Broad |
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What is the target of Cephalosporin? |
Target: Cell wall Spectrum: narrow to broad |
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What is the target of carbapenem? |
Target: cell wall Spectrum: broad |
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What is the target of glycopeptide? |
Target: cell wall spectrum G+ |
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What is the target of cyclic polypeptide? |
Cell wall Spectrum: G+ |
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What is the target of polyketide? |
Protein synthesis Spectrum: broad |
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What is the target of phenicols? |
Protein synthesis Spectrum: Broad |
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What is the target of aminoglycosides? |
Protein synthesis Spectrum: broad |
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What is the target of macrolide/lincosamides Streptogramin? |
Protein synthesis Spectrum: G+ |
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What is the target of quinolones? |
DNA synthesis Spectrum: G+ |
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What is the target of rifamycins? |
mRNA synthesis Spectrum: G+, mycobacteria |
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What is the target of sulfonamides? |
Folate synthesis Spectrum: broad |
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What is the target of nitroimidazoles? |
DNA
Spectrum: Anaerobes |
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What is the target of polypeptides? |
Cell membrane Spectrum: G- |
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How do B-lactam antibiotics work? |
Penicillins and cephalosporins are the most widely used antibiotics (good specificity, low toxicity, good spectrum) - Target cell wall biosynthesis, inhibiting bacterial growth by destabilizing the wall - Bacterial target is the penicillin-binding proteins (PBP) - PBP's help polymerize (cross-link) beta-glycan chains during cell wall formation B-Lactam antibiotics look structurally similar to D-alanyl-D-alanine, fools PBP enzyme into using the antibiotic instead (= competitive inhibition) - Irreversible binding to active site of PBP (non-competitive inhibition) - prevents final cross-linking of peptidoglycan layer in cell wall synthesis - disruption of cell wall synthesis = weak cell walls |
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4 B-lactam resistance mechanisms: |
1) B-lactamase enzymes (most important) 2) Modification of penicillin-binding proteins (also important) 3) efflux pumps (new ones found every day) 4) Decreased permeability (porins in G- bacteria membrane) |
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3 main mechanisms by which bacteria can obtain non-chromosomal DNA: |
Horizontal Genetic Exchange Conjugation = Sex Pilus - Plasmid transfer - Transposon transfer - Integron transfer Transduction = Bacteriophage - incorporation of phage DNA (carrying bacterial DNA) into chromosome or plasmid Transformation - Uptake of DNA fragments from environment |
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What are the 3 transferable genetic elements carrying antibiotic resistance genes? |
1) Plasmids 2) Transposable elements - Transposon - integrons - insertion elements 3) Phages |
