Antibiotic Stewardship Flashcards
What is an antibiotic?
a drug that kills or inhibits growth of microorganisms
What is resistant?
somewhat arbirtray designation that implies that an antimicrobial will not inhibit bacterial growth at clinically achievable concentrations
What is susceptible?
some what arbitratry designation that implies that an antimicrobial will inhibit bacterial growth at clinically acheivable concentrations.
What is MIC?
the minimal inhibitory concentration; the lowest concentration of antimicrobial that inhibits growth of bacterial- commonly used in clinicla labs
What is MBC?
the minimal bacterial concentration; the concnetration of an antimicrobial that kills bacteria. Used clinically only in special circumstances
What is the breakpoint?
the MIC that is used to designate b/n susceptible and resitance (evidance based set by a committee)
What are susceptibility testing methods?
1) MIC
2) Kirby-Bauer Disk diffusion
3) Agar dilution
4) E-test
What is the MIC test?
- dilute antibiotic 2x across solution and when hit a [] that prevents growth
- wells plate for MIC testing (microfilter plate)
- many labs use automated testing and scans determine forma a specific isolate
What it sth Kirby-Bauer Disk Difussion?
- looking at zone of inhibition
- can’t determine MIC directly
- have to compare versus a chart to see if susceptible versus resistent due to [] levels at site of action
What is Agar dilution?
Broth dilution in an augar form
what is the E-test?
-strip with a grandinet of [antibiotic] to inhibit growth of bacteria until [] is too low then IC at the pt. on the strip
When is a fungi resistant?
When MIC>BP
(just becaseu less to use does not mean it is better b/c BP may be lower; adn if BP is signigicantly higher than MIC then the more susceptible
-expamle ciprofloxacin MIC = 2 and BP=2 so resistance
Piplfazo MIC=8; BP=32-64
What are factros that lead to resistance?
ANTIBIOTIC USE!!!!
using antibiotics on foot and animals and when food is not process porperly they are carry ing bacterial and pass onto us
what are the 8 reasons for over use?
Pts: 1) want clear explanation 2) Green nasal discharge 3) need to return to work Physicans concerns 4) pts. expect antibiotics 5) diagnosic uncertianty 6) time pressure
What are teh highest risk pts?
immunocompromized pts
hospitalized pts
invasive devices (central venous catheters)
use on one pts can cause spread to other patient
what the four mechanisms fo resistance?
1) antibiotic degrading enzymes
2) decrease permiability
3) efflux pumps
4) target alterations
Look at figure for cycle of antibiotic resistance acquisiton
selection ofr 1 drug casues resistance to multiple durgs due to linkage (X,Y,Z)
What is b-lactamase?
confer resistance to some, many or all b-lactams antibiotics
- can be on a plasmid
- more potent in gram - bacteria
- benifical for bacteria becasue they are just increasing what they normally are doing
what are b-lactamases more potentent on gram -?
located in the periplasmic space so increased in [] wherease in gram + located outside of the cell wall
What are extended specturm B-lactamases?
B-lactamases that are capable of hydorlysing extened spectrum cephalosporins, penicillins adn aztronam
- usually plasma mediated
- aminoglycoside, ciprofloxacin, and trimethoprim-sulfamethoxazole resistance often encoded on same plasmid
what are class A carbapenemases?
enzymes that degrade carbaphenes
what ocurs to get decreased permeability?
tightens walls so drugs cant get across
-can be an innate or an aquired resistance
why are gram - resistant to vancomyosin?
b/c vancomyocin is to large to get across their 2 membranes
what are teh mechanisms of antibiotic resistance?
1) antibiotic degraadin enzymes
2) decreased permeability
3) efflux pumps
4) target alterations
how are bacteria becoming resistant to vancomyocin?
gram + are changing their D-Ala-D-Ala sequence to D-Ala-D-Lactate
what is conjugation?
plasmid transfer via contact
What is transduction?
tranfer by viral delivery
Waht is transformation?
transfer of free DNA
Waht are teh adverse drug events (DEs)
- hypersensitivity/ allergy
- drug side effect (many pts have to be hospitalized due to this)
- clostridum difficle infection
- increasing health costs
What are the 9 factors to concider when selecting an antibiotic?
1) specturm of coverage
2) patterns of resistance
3) evidence or track record for specified infection
4) achievable serum, tissue or body fluid concnetration
5) allergy (PMHx)
6) Toxicity
7) formutation (IV vs PO)
8) Adherence/Convienience (2x/day or 6x/day)
9) COST!!!
What are the emperic therapy prinipals?
85%
- infection onot well defined (best guess)
- broad spectur
- multiple drugs
- evidance ususally only 2 reandomize controled trials
- more adverse rnx
- more expensive
Waht are the directed therapy priniples?
15%
- infection well defiened
- narrow spectrum
- one, seldom 2 drugs
- evidance usually stronger
- less adverse rxns
- less expensive
What does a negative culture mean?
does not eman it is not a bacterial infection!!! could just mean thatye they have already been txed so supression of the infection
what is the genral trend in teh antibiotic industry?
a general trend V in production of antibiotics; less funding; expensive to make; hard to get physicains to perscribe new drugs
What are the 3 principal reasons of antibiotic market failure>
1) Scientific
2) Economic
3) Regulation (FDA)- no more likely to die of any thing with in 28 day of tx; trial have to be largers
What is the Gain act of 10/1/2012?
- provides exclusivity for antibiotis adn earmarks them for priority review
- must be approved based ont eh bugs they kill regardless of the site of infection!
- pressure to limit adverse effects
what are the goals of antibiotic use?
- prevention or cure of infection w/a minimum of toxicity to pt.
- minimum impact on the pt’s microbial flora (collateral damage)
- minimum impaction on teh microbial flora of other pts/enviorment (colonization pressure, corss-infection – forgetting to wash hands)
What sould a Dr. be aware of when reatreating a pt with in 1 yr?
they should use a new class of antibiotics, becasue of cross resistance
what are teh possible reasons for a high moretality in MRSA bacteriemia?
- delay in effectiv therapy
- differnt pat. population
- higher virulence of isolates
- lower efficacy of vancomycin for MRSA than b-lactams for MSSA
what is collateral damage with regarud to antibiotics?
a term used to refer to ecological adverse effects of antibiotic therabpy, namely the selection of drug-resistant organisms and the unwanted development of colonization or infected mulitdrug resistant organisms
-commonly linked to 2 organisms (cephalosproins, Quinolones)
