21 - Antimicrobials Flashcards
What are the 5 main ways that antibiotics work and give some examples of each?
What is the difference between bactericidal and bacteriostatic antibiotics?
- Cannot use two together as bacteriocidal work best on bacteria that are replicating and bacterostatic stop division
- Bacteriostatic: macrolides, tetracycline
- Bactericidal: penicllin, ceflasporins
What are some ways that bacteria develop resistance to antibiotics?
Mutation: Bacteria can mutate or change their genetic material, allowing them to resist the effects of antibiotics. This can happen spontaneously, or as a result of exposure to low levels of antibiotics.
Horizontal gene transfer: Bacteria can transfer genetic material, including resistance genes, to other bacteria through processes such as conjugation, transformation, and transduction.
Efflux pumps: Bacteria can use efflux pumps to remove antibiotics from the cell before they can do damage. These pumps act like molecular pumps, pushing the antibiotics out of the cell before they can cause harm.
When do we need to drug monitor antibiotics?
Vancomycin monitored every 4th dose
What does it mean when an antibiotic has time dependent or concentration dependent killing?
The major killing effect against an organism is produced by either the time or the concentration of the drug at the binding site
Time dependent: drugs spend a long time at binding sites as have long half life so this is what kills them e.g penicillins and macrolides
Concentration Dependent: need a certain concentration at binding sites e.g aminoglycosides
Why do we use antibiotics in general?
- Post infective treatment
- Prophylaxis before high risk surgery or for those who have conditions like asplenic to prevent infections
What is co-amoxiclav and why is it prescribed as a combination?
Which groups of people are at increase risk of infection?
Which factors helps one determine which antibiotic is the best choice?
- Allergies and reactions e.g metronidazole and drinking
- Hepatic/Renal Impairment or Pregnancy
- What is the likely infectious agent?
- Is the patient in a high risk group? If so use 2nd line antibiotics as likely to be carrying resistant bacteria
What are the adverse events of antibiotics?
- Toxicities
- Allergic reactions
- Idiosyncratic reactions (Type B)
- Ecological effects – C.difficile, selection of resistance
- Drug interactions
What are some antimicrobial stewardship practices in place in UHL?
- Restricted antibiotics need authorisation from microbiology department
- Start broad and then narrow to appropriate antibiotics when get swabs and cultures back
- Questioning if patient actually needs antibiotics, thinking of resistance and side effects, e.g C.Diff
What is the A to F approach of identifying infection in the I5 model?
When can aciclovir be usedin the treatment of herpes simplex virus?
Same for genital, dose depends if immunocompromised or relapsing
Can also be used in varicella zoster and herepes zoster!
Slows the growth of the virus so speeds up the healing process by about half but doesn’t eradicate the virus!
What is the MOA of cephalexin, what are the DDIs and ADRs?
- Cephalosporin - Inhibits cell wall synthesis
- Used for prophylaxis of recurrent UTI, hospital acquired pneumonia, acute pyelonephritis
- DDIs: can increase blood metformin levels
- ADRs: diarrhoea, ab pain, headache, vomiting, thrush, eosinophillia
What is the MOA of azithromycin and clarithromycin, what are the DDIs and ADRs?
Macrolides: stop protein synthesis by having an effect on ribosomal translocation
Used for: resp infections, ear infections and skin/soft tissue infections in those that are allergic to penicillin
DDIs: Clarithromycin with CCBs can cause AKIs, clarithromycin is CYP3A4 inhibitor
ADRs: Hepatotoxicity, Nausea, Diarrhoea, QT prolongation so arrhythmias, anaphylaxis, Steven Johnson syndrome, C.Diff, can aggravate Myasthenia Gravis