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6 Cards in this Set

  • Front
  • Back
List 5 mechanisms of antimicrobial resistance.
1. Enzymatic inhibition
2. Alterations of bacterial membranes
3. Promotion of antibiotic efflux
4. Alterations of bacterial protein targets(ribosomal/cell wall/critical enzymes
5. Bypass of antibiotic inhibition
What is enzymatic inhibition?
It is one of the most common modes of antimicrobial resistance.
An example would be Staph. aureus' resistance to beta lactam antibiotics(penicillin0 is due mainly to the production of beta lactamases, enzymes that inactivate these antibiotics by splitting the beta lactam ring.
Why do many penicillins go after G+ organisms and not G neg?
Because Gram neg bacteria have a lipid bilayer that acts as a barrier to the penetration of antibiotics into the cell.
How do penicillins function when they enter Gram neg bacteria?
Passage of hydrophilic(water soluble) antibiotics through this outer membrane is facilitated by the presence of porins, proteins that form water filled diffusion channels through which antibiotics can travel.
Mutations resulting in the loss of specific porins can occur and may lead to increased resistance to penicillins. (Pseudomonas aeruginosa resistance to imipenam is an example).
Regarding membrane permeability, how are aminoglycosides associated?
Aminoglycosides require active electron transport(proton motive force) which means that a positively charged aminoglycosides molecule is pulled across cytoplasmic membranes of the internal negatively charged cell.
How is resistance associated with these proton forces of aminoglycosides?
The energy generation or the proton motive force that is required for substrate transport into the cell may be altered in mutants resistant to aminoglycosides.
Staph. resistance to aminoglycosides is an example.