Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
67 Cards in this Set
- Front
- Back
|
What are the sites of action for antibiotics?
|
1. Cell wall
2. Cell membrane 3. Nucleic acid synthesis 4. Protein synthesis 5. Metabolic pathway |
|
|
What is the site of action for penicillin?
|
The cell wall
|
|
|
What is the mechanism of penicillin action?
|
PBP
It blocks synthesis and cross-linking of the cell wall. |
|
|
When is penicillin most effective? On what organisms?
|
Gram + during growth phase.
|
|
|
What are the resistance mechanisms to penicillin? (3)
|
1. Limited access to PBP (Gram -)
2. Beta-lactamase 3. PBP modification or decrease in number of PBP |
|
|
What is the action of beta-lactamase and what antibiotic class is effected?
|
Cleavage of the beta-lactam ring in penicillins.
|
|
|
What beta-lactams are able to resist the actions of penicillinases?
|
Methicillin
Nafcillin |
|
|
What cell wall disruptors are able to resist the action of beta-lactamases?
|
Cephalosporin
Cycloserine Bacitracin Vancomysin Methicillin/Nafcillin |
|
|
What are the inhibitors of beta-lactamase? How are they used?
|
Clavulanic acide
Sulbactam Used in combination with penicillinase-sensitive penicillins |
|
|
When would methicillin or nafcillin be used?
|
When a gram + organism has beta-lactamase.
|
|
|
How is methicillin/nafcillin biochemically different from penicillin? What is the potency of methicillin when compared to penicillin?
|
They have bulky R groups at the site of hydrolysis to prevent the action of beta-lactamases
Methicillin is 1/10 the potency of penicillin G |
|
|
What is the mechanism of methicillin resistance?
|
PBP modification or lower affinity PBPs and limited access in Gram - microbes.
|
|
|
What are the broad spectrum penicillins? Why are they broad spectrum?
|
Ampicillin
Carbenicillin Have a hydrophilic group that allow then to access the porins on Gram - |
|
|
What is the site of action of cycloserine? What is its spectrum?
|
cell wall
very broad spectrum |
|
|
What is the mechanism of cycloserine? How is resistance developed?
|
Competitive inhibitor of alanine
Loss of the alanine transport system or elevated levels of alanine racemase and alanyl-alanine synthetase can overcome competition |
|
|
What is the site of action of bacitracin? What is the spectrum?
|
Cell wall
Gram + and Neisseriae |
|
|
What is the mechanism of Bacitracin?
|
prevents the reentry of the lipid carrier in cell wall synthesis
|
|
|
What is the site of action for vancomycin? What is the spectrum?
|
Cell wall
Gram + |
|
|
What is the mechanism of action of vancomysin?
|
Binds to the ala-ala subunits in wall synthesis and blocks the transpeptidation
|
|
|
What is the mechanism of VRE/VRSA?
|
Substitution of lactate for alanine in the cell wall. (ala-lac)
|
|
|
What is the mechanism of VISA?
|
VISA has increased ala-ala units in a thicker and more disorganized cell wall. They act as decoys to bind the drug. It can be overcome with higher doses.
|
|
|
What is the site of action for polymyxin? What is the spectrum?
|
Cell membrane
Gram - |
|
|
What is the mechanism of polymyxin?
|
Long FA tail will disrupt the membrane of gram -. Causes leakage of metabolites.
|
|
|
What drugs can be used against fungal infections?
|
Polyenes
Azoles |
|
|
What is the site of action of polyenes and azoles?
|
cell membrane
|
|
|
What is the mechanism of action for polyenes?
|
Binds to the ergosterol of fungal cells and creates a pore.
|
|
|
What is the mechanism of action of azoles?
|
Blocks the synthesis of ergosterols
|
|
|
What is the mechanism of polyene resistance?
|
Decreased expression of ergosterols or the modification of the binding site.
|
|
|
Why do polyenes have limited use?
|
Nephrotoxic
|
|
|
What are the cell membrane disruptors?
|
Polymyxin
Polyenes Azoles |
|
|
Cell membrane disruptors are used against what type of organisms?
|
Gram -
Fungi |
|
|
What are the DNA/RNA inhibitors?
|
Quinolones
Metronidazole Rifampin |
|
|
Name the Quinolones.
|
Naldizic acid
Ciprofloxacin |
|
|
What is the mechanism of action for quinolones? What is the spectrum?
|
Binds and blocks the DNA gyrase
Gram +/- |
|
|
What is the mechanism of quinolone resistance?
|
Mutation in the DNA gyrase
|
|
|
What is the site of action of metronidazole?
|
DNA inhibitor
|
|
|
What is the mechanism of metronidazole action? what is the spectrum?
|
Reduces the number of ETC proteins and creates toxic intermediates that damage DNA
Used for obligate anaerobes and protozoa |
|
|
What is the mechanism of action for rifampin? What is the spectrum?
|
Binds the DNA-dependent RNA polymerase and blocks initiation.
TB, leprosy, N. meningitidis |
|
|
What is the mechanism of rifampin resistance?
|
Change in the beta-subunit of the DNA-RNA polymerase
|
|
|
What are the protein synthesis inhibitors? (5)
|
Aminoglycoside
Tetracycline Chloraphenicol Lincosamides Macrolides |
|
|
What is the mechanism of action for streptomycin? What is the spectrum?
|
Irreversibly binds the 30S ribosomal subunit
Gram +/-, TB |
|
|
What is the mechanism of streptomycin resistance?
|
Plasmid-mediated enzymatic modification of the drug (acetylation, phosphorylation, adenylation). Also reduced uptake.
|
|
|
What are the aminoglycosides?
|
Streptomycin
Gentamicin tobramycin kanamycin amikacin |
|
|
What is the mechanism of action of tetracycline?
|
Binds the A-site of the 30S ribosomal subunit
|
|
|
What is the spectrum of protein synthesis inhibitors?
|
very broad
|
|
|
What is the mechanism of chloramphenicol?
|
Binds the 50S ribosomal subunit and blocks the peptidyl transferase
|
|
|
What is the mechanism of chloramphenicol resistance?
|
Inactivation with chloramphenicol acetyltransferase
|
|
|
Why does chloramphenicol have limited use?
|
Bone toxicity
|
|
|
What is the mechanism of tetracycline resistance?
|
1. Primarily active efflux
2. Decreased penetration of the drug, 3. lteration of the A-site on the 30S, or enzymatic alteration of the drug. |
|
|
Name the lincosamides.
|
Lincomycin
Clindamycin |
|
|
What is the mechanism of the lincosamides?
|
Binds the 50S and blocks peptidyl transferase
|
|
|
What are the inhibitors of the 30S?
|
Aminoglycosides
Tetracycline |
|
|
What are the inhibitors of the 50S?
|
Chloramphenicol
Lincosamides Macrolides |
|
|
What is the mechanism of action of the macrolides?
|
Binds the 50S and blocks translocation
|
|
|
What is the mechanism of lincosamide resistance?
|
methylation of the ribosome to disrupt the binding site
|
|
|
What is the mechanism of macrolide resistance?
|
methylation of the ribosome to disrupt the binding site.
|
|
|
If an organism has an erythromycin resistance, what other drug is most likely not going to work?
|
the lincosamides--cross resistance with the macrolides.
|
|
|
What drug is substituted in patients with penicillin allergies?
|
Macrolides--erythromycin
|
|
|
What are the metabolic pathway inhibitors?
|
Sulfonamides
Trimethoprim Isoniazid |
|
|
What is the mechanism of sulfonamides?
|
analogs of p-aminobenzoic acid. Blocks the formation of dihydropteroic acid in the folic acid pathway.
|
|
|
What is the spectrum of the metabolic inhibitors?
|
All broad, except for isoniazid which is only used for mycobacteria
|
|
|
What is the mechanism of sulfonamide resistance?
|
dihydropteroate synthetase with lower affinity for the analog
|
|
|
What is the mechanism of action for trimethoprim?
|
analog for DHFolic acid. Block folic acid metabolism.
|
|
|
What is the mechanism for isoniazid?
|
Inhibitis the synthesis of mycolic acids
|
|
|
What organisms make mycolic acids and what drug inhibits their production?
|
mycobacteria make it and the drug is Isoniazid
|
|
|
What antibiotics are bacteriostatic?
|
Tetracycline
Chloramphenicol Lincosamides Macrolides Sulfonamides Trimethoprim |
|
|
Name the polyenes.
|
Amphotericin B
Nystatin |
