Antibiotic Action Flashcards
What are the three classes of antibiotic which inhibit cell wall synthesis?
Penicillin, cephalosporins, glycopeptides
What are the three mechanisms of antibiotic action?
Inhibition of cell wall synthesis
Inhibition of protein synthesis
Inhibition of nuclei acid synthesis
What are penicillin and cephalosporins ?
B-lactams
What effect on a bacterium do antibiotics which act on the cell wall have?
Bactericidal effect
Which type of bacteria are effected by antibiotics which inhibit cell wall synthesis?
Gram positive
What is an example of a glycopeptide and what does it do?
Vancomycin - inhibits precursors of peptidoglycan so cell wall cant be synthesised
Used instead of b-lactams in bacteria which are resistant and produce b-lactamase
Fights MRSA
Which antibiotic class inhibits protein synthesis in gram negative bacteria?
Aminoglycosides.
What is an example of an aminoglycoside and what does it do?
Gentamicin - causes mis-reading on RNA and thus incorrect protein synthesised
Which antibiotic can be used instead of penicillin and what form of action does it take on which bacteria?
Macrolides. Bactericidal and bacteriostatic action on gram positive bacteria. Used for people with penicillin allergies
An example of a macrolide and its purpose
Erythromycin Treats abnormal pneumonia
Also substitution for penicillin in people with allergies
Example of oxazolidinones and form of action (3)?
Linezolid. Inhibit protein synthesis in gram positive. Static or cidal. Treats MRSA and pneumonia
What is a cyclic lipopeptide and an example? What does it treat?
Bactericidal on gram positive, inhibiting protein synthesis. Bactericidal. E.G. daptomycin
Serious skin infections or Severe sepsis by gram + bacteria
Which class of antibiotics can inhibit nucleic acid synthesis?
Fluoroquinolones
Which bacteria do fluoroquinolones act against and by which mechanism? What is an example?
Gram negative - bactericidal. Levofloxacin or Ciprofloxacin
What is ciprofloxacin used for? How is it administered?
A fluoroquinolone to treat pseudomonas infections. Only oral solution
What are tetracyclines and a use?
Inhibits protein synthesis in gram positive bacteria. Bacteriostatic. Treats chlamydia. Not for children under 12 or pregnant women
Administration and side effects of linezolid
Orally. Cause bone marrow suppression. Treats MRSA
Which drug is used when a patient has a very severe or high risk, complicated bacterial infection?
Carbapenems
What is an emerging issue with use of carbapenem?
In many countries CPE is becoming more prominent (CPE is bacterium that produce carbapenemase which breaks down carbapenems) (CRE is just bacteria which are resistant to carbapenems)
What is a carbapenem?
A b-lactam which is used to combat multi drug resistant (MDR) bacteria
What is b-lactamase?
Bacterial enzymes which break the b-lactate ring of antibiotics and render them inactive
How can we combat b-lactamase?
Administering co-amoxiclav (amoxicillin + clavulanic acid, a b-lactamase inhibitor)
Which bacteria are b-lactamases found in?
Gram positive and negative bacteria
How is resistance to b-lactams developed on a cellular level?
Penicillin binding site is mutated on bacterium so it can no longer bind, so
What’s an example of a bacteria that is immune to b-lactams and what can be used instead?
MRSA. Vancomycin
What is gentamycin and what is it used for?
Aminoglycoside, treats gram N, bactericidal. Little resistance in UK
When do we use aminoglycosides and why?
We use aminoglycosides like gentamycin for serious gram negative bacteria because it is toxic
What is the therapeutic margin?
Small therapeutic margin = small difference between effective and toxic dose. Must be monitored closely
Why must age be considered when prescribing antibiotics?
In kids some may affect cartilage development
Which antibiotics are safe to use in pregnancy?
Penicillin and cephalosporins
How must antibiotic intake be altered in patients with renal failure or compromised liver?
Must be decreased or another therapy used. Antibiotics are excreted in kidneys and metabolised in liver
What is the spectrum of an anti microbial agent?
The range of microbes which it may attack
Mono therapy vs combination therapy + benefits
Monotherapy is the use of 1 antimicrobe. Combination may use +1. Can have a synergistic effect or an antagonistic effect
What may lead to synergistic or antagonistic effects in combination therapy?
2 static/2 cidal = synergistic
1 static + 1 cidal = antagonist
What is the M.I.C. And how do we measure it?
Minimum inhibition concentration. Minimum drug required to inhibit growth of bacteria. Measure this with E test
What happens when an organism has an M.I.C different to the nationally agreed level?
Higher means its resistant to the drug and lower means its sensitive to the drug
Name the 5 antibiotics which inhibit protein synthesis in bacterium.
Aminoglycoside
Macrolide
Tetracycline
Oxazolidonone
Cyclic lipopeptide
When is flucloxacillin used?
Used for staph and strep gram positive skin infections. It’s a b-lactam
