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15 Cards in this Set
- Front
- Back
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bacteriostatic and reversible
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agents that prevent protein synthesis
exception is aminoglycosides (bactericidal/irreversible) |
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generally bactericidal
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agents affecting nucleic acid metabolism
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time-dependent killers, bactericidal
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beta-lactams (cell wall inhibitors)
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bactericidal with concentration dependence
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agents acting on bacterial cell wall directly
polymyxin, daptomycin |
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bactericidal agents should be used in patients with impaired immune defense
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endocarditis, meningitis, infections in patients with neurotropenic cancer (anticancers suppress immune system)
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selective toxicity
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to adversely affect one type of cell (bacteria) and spare normal human cells
penicillin is a good example because it targets cell wall of bacteria only and spares the normal human cells |
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Beta-lactamases
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can cleave the beta lactam bond, which inactivates the antibiotic because it binds to PBP's
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R side chains of beta-lactam ring determine spectrum of antibacterial activity and pharmacological properties
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affinity for PBP, resistance to penicllinase, ability to penetrate gram neg., resistance to stomach acid, PK
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how do beta-lactams work?
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they bind PBP's, then PBP is unable to cross-link peptidoglycan chains
cant synthesize a stable cell wall leads to lysis from osmotic pressure |
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beta-lactam resistance
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Beta-lactamase (cleave beta ring by cutting beta lactam bond) these include penicillinases and cephalosporinases
MRSA- methicillin resistant staphylococcus aureus (beta lactam drugs dont work agains MRSA, because PBP (drug target) is altered in MRSA and beta lactams cant bind PBP |
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vancomycin
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inhibits formation of peptidoglycans in cell wall construction
does not cross lipid membrane of gram neg. (gram neg. bacteria innately resistant) acquired resistance most often due to amino acid alterations in side chain peptidoglycan building blocks (drug binding site is mutated) |
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bacitracin
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interferes with transport of peptidoglycan precursors across cytoplasmic membrane, cell wall inhibited
toxicity limits its use to topical applications |
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tetracycline resistance
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efflux pumps-pumps antibiotic out
ribosome protection-bacterial proteins that interfere with tetracycline binding, they compete with drug for binding, they can dislodge drug from the ribosome and increase the apparent kd value |
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aminoglycosides resistance
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inactivation of drug by microbial enzymes--> aminoglycoside modifying enzyme (AME), these enzymes can phosphorylate, adenylate, or acetylate drugs and with these chemical groups added to the drug it will be inactivated
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macrolide(erythromycin) resistance
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active efflux pumps
ribosome modification- bacterial enzyme (methylase) alters the macrolide binding site on the bacterial ribosome so the drug cannot bind |
