Microbiology - Antimicrobials 2 Flashcards
what do you need to consider when prescribing antibiotics?
CHAOS
Choice of correct antimicrobial depends upon..
Host characteristics (renal function, age, etc)
Antimicrobial susceptibilities of the..
Organism itself and the
Site of infection (bone, CSF, urine etc)
what do you need to consider when picking the drug?
- narrow spectrum
- choice based on diagnosis
- consider local sensitvities
- patient characteristics
- cost
- pharmacokinetics
- route of admin
- dosage
when are IV antibiotics recommended?
- if infection is serious
- deep infection (osteomyeltitis, endocarditis)
- patient is not absorbing properly
- treat CNS infection
what is the MIC?
minimum drug concentration required to inhibit growth of organism
how do you use the MIC to determine if antibiotic is sensitive?
regulatory bodies set cut offs/ breakpoints
MIC < breakpoint = sensitive
MIC > breakpoint = resistant
what is important to do before starting empirical therpay?
collect specimens for culture
cover can then be changes based on culture results
how can you identify organisms?
- gram staining
- rapid antigen detection (immunofluorescence, PCR)
what factors will affect the local concentration of the antimicrobial?
- pH at infection site
- lipid solubility
- ability to penetrate the BBB
when do/ don’t use PO?
- easy
- avoid if poor FI function or vomiting
when do/don’t use IM?
- not an option for long term use
- avoid if bleeding tendency
what are the downsides to topical antimicrobials?
- limited application
- may cause local sensitisation
when is it recommended to switch to PO?
- in hospital for infections when pt has stabilised after 48 hours of IV tx
in which circumstances should you not switch to PO?
- CNS infections
- severe infections e.g. osteomylelitis, endocarditis
what is the pattern of activity of type 1 antibiotics?
- concentration dependent killing
- prolonged persistent effects
- Cmax most important factor
- higher Cmax better the clinical outcome
- but achieveing high Cmax needs to be balanced with risk of adverse effects
which antibiotics have type 1 activity?
- aminoglycosides
- daptomycin
- fluoroquinolones
- ketoides
in which patients do you need to be careful giving aminoglycosides?
- if pt has renal failure
- but if renal failure is due to sepsis, give full dose and worry about nephrotoxicity later
