4. Antimicrobials Flashcards
What are 4 common target of antibiotics?
Cell wall synthesis
Protein synthesis
Cell membrane function
Nucleic acid function
What antibiotics target cell wall synthesis?
Glycopeptides
Beta-lactams
What antibiotics target cell membrane function?
Polymixins
What antibiotics target protein synthesis?
Tetracyclines
Aminoglycosides
Macrolides
What antibiotics target nucleic acid synthesis?
Quinolones
Trimethoprim
Rifampicin
What is MOA of penicillin?
Binds to penicillin binding protein, preventing cross-linking of peptidoglycan in cell wall.
What is an example of a glycopeptide antibiotic?
Vancomycin
What is the MOA of vancomycin?
Attaches to side chains of amino acids and prevents them being cross-linked in the cell wall.
What is an example of a quinolone?
Fluoroquinolones - Cyprofloxacin
What is the MOA is cyprofloxacin?
Inhibits topoiosomerase, causing supercoiling and strand breakage of DNA.
What are 3 types of resistance?
Intrinsic
Aquired
Adaptive
What is intrinsic resistance?
There is no target or access for the drug, usually permanent.
E.g penicillin won’t work again pseudonomas
What is acquired resistance?
Bacterial resistance as a result of acquisition of new genetic material or mutation which aids resistance.
Usually permanent
What is adaptive resistance?
Organism responding to stress such as sub-inhibitory level of antibiotics
Usually reversible
What are 3 mechanisms of resistance?
- Drug-inactivating enzymes
- Altered target
- Altered uptake
What is an example of drug inactivating enzymes leading to resistance?
B-lactamase enzymes produced by organisms which inactivate beta lactam antibiotics.
How can altered target lead to antibiotic resistance?
If the target enzyme has lowered affinity for an antibacterial drug.
What is an example of resistance as a result of an altered target?
MRSA - PBP2a
How can altered uptake of an antimicrobial lead to antibiotic resistance?
Increased efflux via P-glycopeoteins decreases intracellular concentration to sub-inhibitory.
What are the 3 mechanisms of horizonal gene transfer of extrachromosomal plasmids in bacteria?
Transformation
Transduction
Conjugation
How can you measure antibiotic sensitivity?
Disc sensitivity testing
What is minimum inhibitory conc?
The lowest concentration of antibiotic that leads to no antibacterial growth.
Which penicillin antibiotic is mainly active against streptococci?
Penicillin
Which penicillin antibiotic is has activity against gram -ve as well as gram +ve bacteria?
Amoxicillin
What bacteria is flucloxacillin active against?
Staphylococci and streptococci
What antibiotic can be given to overcome beta-lactamase enzyme resistance?
B-lactamase inhibitor + Beta lactam antibioitic
- Co-amoxiclav
Why are cephalosporins often used instead of penicillins?
Better at withstanding beta lactamase enzymes
What is an example of a cephalosporin?
Cefriaxone -meningitis treatment as enters CSF
What must be considered when prescribing vancomycin?
Narrow therapeutic window - therapeutic drug monitoring needed
What is the MOA of trimethoprim?
Inhibits folic acid synthesis
What is trimethoprim used to treat?
UTI
What anti-viral drug is commonly used?
Acyclovir
What is the MOA of acyclovir?
Inhibits viral DNA polymerase
What is antimicrobial stewardship?
Interventions to improve and measure approprite use of antimicrobials
What 4 things does antimicrobial stewardship promote?
- Selection of optimal antimicrobial drug regimen
- Appropriate dose
- Duration of therapy
- Route of administration
What is the aim of antimicrobial stewardship?
Achieve optimal clinical outcomes
Minimise toxicity and adverse effects
Reduce costs of infections
Limit the selection for resistant strains
What are 3 ways of stewardship intervention?
- Persuasive - education, reminders, feedback
- Restrictive - prior authorisation, automatic stop orders
- Structural - computerised records, rapid lab tests, quality monitoring
