Antibiotics Flashcards
What does bactericidal mean?
Destroying or killing bacteria
What does bacteriostatic mean?
Stopping division and replication of bacteria, slowing growth
Why might it be counterintuitive to give a bactericidal and bacteristatic antibiotic at the same time?
Bactericidal antibiotics work optimally when bacteria are dividing at their normal rate. As bacteriostatic antibiotics slow rate of division, bactericidal agents don’t work as well.
What are the 5 main ways by which anti-microbials work?
- Inhibiting cell wall synthesis
- Inhibiting nucleic acid synthesis
- Stopping metabolite function
- Inhibiting cell membrane synthesis
- Inhibiting protein synthesis
How does penicillin work?
Name 4 types of penicillin
- Amoxicillin
- Flucloxacillin
- Co-amoxiclav
- Phenoxymethylpenicillin (penicillin V)
How do ceflasporins work?
Act on the cell wall → bactericidal
Give an example of a cephalosporin
Cephalexin
How do Quinolones work?
Inhibit bacterial DNA/RNA synthesis
Give an example of a quinolone
Ciprofloxacin
How do macrolides work?
Inhibit bacterial protein synthesis → bacteriostatic
Give 2 examples of macrolide antibiotics
Azithromycin
Clarithromycin
How do tetracycline antibiotics work?
Inhibit bacterial protein synthesis → bacteriostatic
Give an example of a tetracyline antibiotic
Doxycylcine
How do aminoglycosides antibiotics work? e.g. gentamycin?
Inhibit protein synthesis of bacteria
How do glycopeptide antibiotics work e,g, vancomycin
Act on bacterial cell wall → bactericidal
How do carbopenam antibiotics work?
Act on bacterial cell wall → bactericidal
How can bacteria develop resistance to antibiotics?
- Develop efflux pumps
- Develop inactivating enzymes
- Develop immmunity that bypasses damage to bactiera
- Target modification
Why do antibiotics need to be monitored? Give examples of 2 antibiotics in particular that need monitoring
- Narrow therapeutic window
- Maximum effect of antibiotic
- Risk of toxicity
- e.g. vancomycin and gentamicin
What is time dependent killing of bacteria (with antibiotics)?
For effective killing, minimum inhibitory concentration needs to be maintained over a period of time
Increasing concentration won’t have any more effect
What is concentration dependent killing of bacteria?
Aim it to get the maximum dose (CMax) of antibiotic for effective killing
High doses at high concentration
For what reasons might you use antibiotics?
- Short term management of a bacterial infection
- Prophylaxis in acute setting e.g. high risk procedures (joint/ bowel operations)
- Long term prophylaxis (if suitable, often not reccommended)
What are the 2 ‘ingredients’ of co-amoxiclav? What is the purpose of each?
Clavulanic acid:
- Inhibits the effects of beta lactamase enzymes so amoxicillin can work better
Amoxicillin:
- Acts on cell walls of bacteria
What factors govern antiobiotic choice?
Multifactorial:
- What is the likely source of infection?
- Source of infection lends themselves to common bacteria groups
- Is the patient ‘high risk’ (immunosuppressed/ neutropenic)
- Previous results with antibiotics
- Special groups: renally impaired, pregnancy, hepatic impaired
- Allergies and reactions
What are the 5 ‘i’s of antimicrobial stewardship?
- Identify
- Isolate
- Investigate
- Inform
- Initiate treatment
Give an example of an antiviral drug?
Aciclovir
What are the principles of anti-microbial stewardship?
- Does the patient need antibiotics
- Start broad (empitical treatment) and narrow to more appropriate antibiotics
When would you use aciclovir?
Herpes simplex virus
Dose depends on whether it’s 1st presentation vs relapse
