Microbiology 3 - Antimicrobial Agents 2 Flashcards
What mnemonic can be used to help decide which antibiotic to use?
CHAOS Choice depends on the: Host characteristics (are they pregnant, are they a child, do they have seizures, are they allergic) Antimicrobial susceptibilities of the 1. Organism itself, as well as the 2. Site of infection
Additionally:
FOLLOW LOCAL GUIDELINES
Consider pharmacokinetics, route of administration, dosage (age + weight, renal/hepatic function)
What is the Minimum Inhibitory Concentration and Breakpoint of an antibiotic useful for?
Working out sensitivity
MIC = minimum drug concentration required to inhibit the growth of an organism in culture
Compare the MIC with a standard breakpoint (level of therapy where the antibiotic is associated with clinical success)
MIC > breakpoint = resistant
MIC < breakpoint = sensitive
What antibiotic should be given for gram pos cocci in clusters?
Flucloxacillin
What antibiotic should be given empirically for gram neg cocci?
Ceftriaxone (could be meningococcus)
What is the “eagle effect”?
Increasing the penicillin dose –> decreasing antibacterial activitity after a point
How does the choice of antibiotic to treat UTI differ between community and hospital?
Community: nitrofurantoin/ trimethoprim
Hospital: cephalexin/ augmentin
What is empirical and definitive therapy?
Empiric therapy is treating the patient using our best guess - based on differential diagnosis and local guidelines
Definitive therapy is commenced once culture results are received
TAKE CULTURE SAMPLES BEFORE STARTING EMPIRIC THERAPY - to prevent results from being affected
Once you know an organism’s susceptibility, should you switch their antibiotics?
Based on susceptibility, try to de-escalate to the narrowest spectrum antibiotic possible -> reduces side-effects, reduces likelihood of C. diff growth, reduces alterations to gut flora etc.
