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21 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Ribosomal differences btw. mammals and bacteria
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- bacterial ribosome is smaller (70S vs. 80S)
- mammal subunites are 50S and 30S, bacterial subunites are 60S and 40S - high doses may interfere with mitochondrial ribosomes (chloramphenicol or tetracyclines). |
p 373
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Tetracycline mechanism of action
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- enter into organism by passive diffusion and active transport
- binds reversibly to 30S ribosomal subunit - blocks access of amino acyl-tRNA to the mRNA-ribosome complex - inhibits protein synthesis |
p 373
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Tetracycline spectrum
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- gram-positive and gram-negative bacteria
- other non-bacterial organisms |
p 374
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Tetracycline resistance
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- R factor
- Mg2+ dependent active efflux of the drug - mediated by plasmid-encodid TetA - resistance to one means resistance to all - most penicillinase-producing staphylococci insensitive |
p 374
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Tetracycline absorption
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- adequate but incomplete oral absorbtion
- dairy intake forms nonabsorbable chelates or tetracyclines (due to Ca2+) - chelates also formed with divalent and trivalent cations (antacids) |
p 374
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Doxycycline
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- tetracycline
- fully absorbed orally - preferred tetracycline for parenteral administration - used when renally compromised, preferentially excreted via bile |
p 374
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minocycline
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- tetracycline
- fully abosrbed orally - enters brain and CSF in absence of inflammation - appears in tears and saliva - vestibular effects |
p 374
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Demeclocycline
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- tetracycline
- phototoxicity |
p 375
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tetracycline distribution
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- enter CSF, but only minocycline is therapeutic
- concentrate in liver, conjugated to form soluble glucuronides - secreted into bile, can be reabsorbed and enter urine - cross placental barrier - concentrate in fetal bones and dentition - excreted in breast milk |
p 375
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tetracycline adverse effects
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- gastric discomfort
- deposited in bone (discoloration/hypoplasia of teeth, temporary stunting of growth) - fatal hepatotoxicity in pregnant women with high doses and pyelonephritis - phototoxicity (tetracycline, doxycycline and demeclocycline) - vestibular effects (minocycline) |
p 375
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Tigecycline
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- glycylcycline
- bateriostatic - reversibly binds to 30S subunit - broad spectrum activity |
p 376
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Aminoglycosides
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- amikacin
- gentamicin - neomycin - streptomycin - tobracycin - derived from streptomyces, ends in -mycin - derived from micromonospora, ends in -micin |
p 377
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Aminoglycoside mechanism
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- diffuse through porin channels in outer membranes
- oxygen-dependent system transport drug across cytoplasmic membrane (therefore not effective against anaerobes) - binds to 30S subunit - depletes polysomes, interrupts polysome disaggregation and assembly - synergistic with β-lactam antibiotics |
p 377
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Aminoglycoside spectrum
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- aerobic gram-negative bacilli including P. aeruginosa
- bactericidal |
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neomycin
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- aminoglycoside
- highly nephrotoxicy - parenteral only (topical, oral) |
p 378
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Aminoglycoside toxicity
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- ototoxicity (accumulates in endolymph and perilymph)
- nephrotoxicity (retention in proximal tubular cells) - neuromuscular paralysis (counter with calcium gluconate or neostigmine) - allergy (contact dermatitis with neomycin) |
p 379
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Macrolides
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- azithromycin
- clarithromycin - erythromycin - telithromycin (ketolide) |
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Macrolide mechanism
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- bind irreversibly to 50S subunit
- inhibit translocation - bacteriostatic |
p 379
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Erythromycin
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- macrolide
- same as penicillin G (used when allergic to penicillin) |
p 379
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Clarithromycin
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- macrolide
- similar to erythromycin - effective against Haemophilus influenzae |
p 380
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Azithromycin
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- macrolide
- preferred for urethritis from Chlamydia trachomatis - activity against Mycobacterium avium-intracellular in HIV |
p 380
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