AM - Antibiotic Action Flashcards
What are the 3 ways antibiotics act?
- Inhibiting Cell Wall Synthesis
- Inhibiting Protein Synthesis
- Inhibiting Nucleic Acid Synthesis
example of antibiotics that inhibit cell wall synthesis?
Penicillins, Cephalosporins & Glycopeptides
Example of antibiotics that inhibit protein synthesis?
Aminoglycosides (Gentamicin) Macrolides (e.g. Erythromicin) Tetracycline Oxazolidinones (Linezolid) Cyclic Lipopeptides (Daptomycin)
Example of antibiotics that inhibit nucleic acid synthesis?
Quinolones
E.g. Ciprofloxacin & Nalidixic acid
Why dont cell wall synthesis inhibitors affect human cells?
Because they lack cell walls
How do B-lactams work?
- Bind to PBPs
- Inhibits carb chain cross-linking
- Peptidoglycans can’t be formed
- Autolytic enzymes kill the cell
What are PBPs?
Penicillin Binding Proteins
Enzymes that synthesize cell wall
What was the first antibiotic discovered?
Penicillin G [Benzyl Penicillin]
Why are many gram -ve bacteria resistant to Benzyl Penicillin?
Gram -ve bacteria have a relatively impermeable cell wall.
How are cephalosporins generally grouped?
By Generations (usually chronological)
How do Glycopeptides inhibit cell wall synthesis?
Inhibits assembly of peptidoglycan precursors
On what bacteria do glycopeptides act?
Glycopeptides act on Gram +ve bacteria
Examples of Glycopeptides?
Vancomycin & Teicoplanin
Why are glycopeptides delivered parenterally?
Theyre not absorbed in the gut
Whats the dosage regime for Teicoplanin?
Once daily
Compare Vancomycin & Teicoplanin?
Teicoplanin is less toxic
Same spectrum of activity
Why must an IV vancomycin infusion be carefully monitored?
Its extremely toxic and can cause tissue damage if it leaks out the veins.
Possible side effects of vancomycin?
Ototoxicity
Nepthrotoxicity
Skin Rashes
Why do we monitor Vancomycin trough levels?
To ensure its level stays within therapeutic range
Why don’t protein synthesis inhibitors affect humans?
There are differences between the bacterial & mammalian ribosomes
What 4 types of protein synthesis inhibitors are there?
Aminoglycosides
Macrolides & Tetracyclines
Oxazolidinones
Cyclic Lipopeptide
What do aminoglycosides treat?
Gram -ve bacteria & sometimes Staphylococci
How are aminoglycosides administered?
Parenterally rather than orally
Whats the most common aminoglycoside?
Gentamicin
What are the possible side effects of Gentamicin & how do we avoid them?
Ototoxicity & Nephrotoxicity
Using a careful dosing regime & serum level monitoring
What are common macrolides & what do they treat?
Erythromicin & Clarithromicin
Treat gram +ve infections when people are penicillin allergic
What bacteria are often resistant to macrolides?
Many staphylococci & Streptococci are resistant to macrolides
Whats the only common oxazolidinone?
Linezolid
Given orally
Treats MRSA
Whats the main Cyclic Lipopeptide & what does it treat?
Daptomycin
Treats gram +ve bacteria, mainly MRSA
In what two ways do antibiotics inhibit nucleic acid synthesis?
By interferin directly in the process
By blocking supply of precursors
What are the 2 common categories of Nucleic acid syntehsis inhibtors?
Co-Trimoxazole
Fluoroquinolones
What makes up co-trimoxazole?
Trimethoprim & sulphamethoxazole
Why is co-trimoxazole used to treat chest infection?
Co-trimoxazole is used for chest infections because its less likely than cephalosporins to cause a CDI
What is trimethoprim alone used to treat?
Urinary Tract Infections
Example of a fluoroquinolone?
Ciprofloxacin, directly inhibits DNA synthesis.
Most effective against Gram -ve
Why cant ciprofloxacin be used in kids?
It interferes with cartilage growth
How is ciprofloxacin delivered?
Orally or Parenterally
Example of a newer quinolone?
Levofloxacin
What is levofloxacin used for?
Treating chest infections
Its more effective than older quinolones like ciprofloxacin against gram +ve bacteria.
