Antibiotics Flashcards
What is the mechanism of action of penicillin?
They bind to PBP in the inhibition of peptidoglycan synthesis and activation of autolytic enzymes in the cell wall.
Is penicillin bactericidal or bacteriostatic?
Bactericidal
How does resistance happen through penicillin?
- production of betalactams
- lack of PBPs or altered version of it
- Efflux of drug out of the cell
- Failure to synthesize peptidoglycans such as mycoplasmas or metabolically inactive bacteria. (natural resistance by bacteria)
What properties of penicillins is the same in the drug structure?
6-aminopenicillanic acid
What are the two types of penicillin?
Penicillin G - V
Explain the properties of penicillin G.
Highly active against gram-positive bacteria and spirochetes.
Destroyed by beta-lactams
Acid labile (not used orally)
Available as aqueous penG , Procaine G and Benzathine Pen G ( the last two are IM only)
Explain the properties of penicillin V.
More acid-stable but still needs to be taken on an empty stomach.
When is penicillin the drug of choice?
Streptococci - pneumenococci - meningococci - spirochetes - clostridia - anaerobic gp rods and actinomyces
Also enterococci and for these gram + is good.
Explain the properties of cloxacillin compared ti the other version of it?
Antistaph drug - Canadian choice of methicillin and nafcillin - MRSA not effective
When do you use oral and Iv versions of cloxacillin?
Oral is for minor cases and IV is for extreme cases.
What are the properties of Methicillin - cloxacillin - nafcillin - flucloxacillin - dicloxacillin?
They have resistance to beta-lactams.
They are designed for staph aureus.
They are less gram p activity otherwise and hence not as good for streptococci.
The use for staphylococcal infections NOT MRSA.
What are the properties of aminopenicillins?
They are for both gram p and gram n.
They also get destroyed by beta-lactams.
Use: streptococci - enterococci - Neiserria sp.
non betalactam producing H.influenza - E.coli - P.mirabilis - Salmonella
What are the properties of Ampicillin?
They are part of the aminopenicillins family.
Used IV.
More acid stable than natural penicillins
poor bioavailability
What are the properties of Amoxicillin?
They are part of the aminopenicillins family.
Used orally
Better absorption than ampicillin
Also, available combined with clavulanic acid (beta-lactamase inhibitor.
Clavulanic acid doesn’t have any antibiotic activity.
