Therapeutics - General Principles Pt 2 Flashcards by amanda kastel

Q

what is MIC (minimum inhibitory concentration)

A

an indicator of antibiotic potency

It’s the lowest ab concentration that prevents visible growth of the bacteria after spending 24 hours in vitro

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Q

true or false

MIC values are very specific

A

TRUE

very specific— 1 drug-1 bug

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Q

3 methods of antimicrobial suceptibility testing

A

broth microdilution
E-test
Kirby-bauer test (zone of inhibition)

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Q

who establishes the MIC breakpoints (reference values) for each organism to each antibiotic

A

CLSI (clinical laboratory standards institute)

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Q

organisms can be _____,_______, or ______ to the antibiotic

A

susceptible, intermediate, or resistant

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Q

what is the name of the cumulative antibiotic “report card” specific for each hospital

A

an antibiogram

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Q

an antibiogram is useful for deciding ______ antimicrobial therapy

A

empiric

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Q

in an antibiogram, if the antibiotic has a high value to the organism, is it good or bad?

A

GOOD

means that it works against the organism a high % of the time
(% susceptibility)

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Q

when staph epi comes back in the sample, what are some important considerations

A

-could be a contaminant

-may be actual infection tho - NEED TO SEE IF THEY HAVE RISK FACTORS (ie: IV drug user or use medical devices often)

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Q

gram negative rods, non lactose fermenting

A

pseudomonas

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Q

which class of antibiotics cover pseudomonas (aerobic gram negative) but do not penetrate the lungs well

A

aminoglycosides

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Q

is pipercillin-tazobactam a good empiric choice for pseudomonas

A

yes - but need to look at antibiogram to confirm

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Q

organism MIC is 2 and MIC susceptibility breakpoint, according to CLSI, is less than or equal to 1

does this mean the organism is susceptible or resistant to the antibiotic?

A

RESISTANT

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Q

MIC of organism is 4 and MIC susceptibility breakpoint is less than or equal to 4

is it susceptible or resistant to the antibiotic

A

technically susceptible, but not preferred to use because it’s just at the breakpoint

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Q

does cefepime penetrate into the lungs and can it be used for a respiatory infection

A

YES

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Q

true allergy, toxicity, or intolerance

diarrhea with doxycycline

A

intolerance

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Q

true allergy, toxicity, or intolerance

thrombocytopenia with linezolid

A

toxicity

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Q

true allergy, toxicity, or intolerance

SJS with bactrim

A

true allergy

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Q

true allergy, toxicity, or intolerance

nephrotoxicity with gentamicin

A

toxicity

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Q

true allergy, toxicity, or intolerance

hives and SOB with penicillin

A

true allergy

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Q

IGE mediated hypersensitivity reactions – what is onset time?
what is an example?

A

within 1 hour - SUPER QUICK

ex - anaphylaxis

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Q

around ______% of US pts report having pen allergy, but only ___% are truly allergic

A

10%, less than 1%

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Q

important consideration for someone that had an IGE-mediated pen allergy years ago

A

around 80% of pts with this allergy lose their sensitivity after 10 yrs!!!
decreases by 10% each year you avoid penicillin

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Q

cephalosporin cross reactivity with pen allergy is around ___%

which generations is it less common

A

3%

as you move up to 5th gen, cross reactivity rate keeps decreasing

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why are false pen allergies so detrimental

suboptimal treatment, more expensive, antiobitc resistance, unnecessary broadspectrum

most ab's are eliminated how?

renally

how is age a consideration when giving antibiotics

likely pathogen can differ based on age (ie - bacterial meningitis) ceftriaxone avoided in neonates bc of hyperbilirubinemia ability to eliminate certain drugs (ie over 65 = decline in renal function)

how can hepatic function be estimated

child pugh score

3 pregnancy and lactation concerns with antibiotics

teratogencity altered pharmacokinetics antibiotic conc in breast milk

name 3 drugs that can cause hemolytic anemia in patients with GDPDH deficiency

dapsone nitrofurantoin primaquine

how are pts with diabetes a special consideration when giving antibiotics

poor peripheral blood flow --- more difficult to treat

chronic lung disease, cystic firosis, and immunosuppressive diseases - how are they a consideration in antibiotic treatment

different pathogens immunosuppressed have higher risk of infection

concern with fluoroquinolones and antacids

they can chelate

how is rifampin a major concern with drug interactions

its a major CYP450 inducer

linezolid + _______ is a big DDI

SSRIs -- risk of serotonin syndrome

which 2 antibiotic classes have a side effect of QT prolongation

macrolides and quinolones

give an example of how dosing of aminoglycosides can differ based on the location of the infection

uncomplicated UTI vs severe infection aminoglycosides penetrate into the urine well -- dont need a veru high dose

differentiate between the ability of cefepime vs pipercillin-tazobactam to penetrate into the CNS

cefepime is much better pipercillin-tazobactam is too big

differentiate between the ability of colistin vs polymyxin B to get into the urine

polymyxin does not colistin is better

can we use daptomycin in pneumonia?? why or why not

NO it gets inactivated by the lung surfactants

first and second line for MRSA pneumonia

vancomycin 2nd line is linezolid DO NOT USE DAPTOMYCIN!!!!!!!!!! gets inactivated by lung surfactants

pt spent 14 days in the hospital what is 1 bacteria we definitely need to cover for and what are 2 choices

pseudomonas use pipercillin-tazobactam or cefepime

if a very severe infection, do we use IV or PO explain

we can start IV and then switch to PO once controlled

beta lactams use conc or time dependent killing

time dependent

differentiate between the dosing frequency of time dependent killing vs concentration dependent

time dependent - DOSED MORE FRWQUENTLY (like Q8 or Q6) conc dependent dosed less frequently

a very high MIC means more or less resistant

more resistant

name 2 antibiotic classes that use concentration dependent killing

aminoglycosides and fluoroquinolones

how do we want the infusion of beta lactams to be and why

PROLONGED INFUSION of 304 hours over traditional 30mins- it's time dependent!! want to maximize duration that the pathogen is exposed to the beta lactam time over MIC - want maximal time

prolonged infusion of beta lactams is particularly beneficial in what 2 scenarios

crtically ill patients pathogens with high MIC

aminoglycosides are time or concentration dependent killing therefore, how are they administered

concentration at a HIGH DOSE once daily ie: gentamicin is 5-7mg/kg Q24H instead of 1-2mg/kg Q8H

aminoglycosides are conc dependent killing and thus give higher doses less frequently give specific EX with amikacin

15mg/kg Q24H instead of 7.5mg/kg Q12H

3 benefits of administering aminoglycosides Q24H instead of more frequently

easier to administer easier drug monitoring decreased nephrotoxicity of aminoglycosides

give 2 secnarios when we may use combination therapy to broaden the spectrum of coverage

-mixed infection -nosocomial infection

3 ex when we may use combination antimicrobial therapy

-broaden spectrum -synergy -prevent resistance

give an example of combination therapy for enterococcal endocarditis

beta lactam + aminoglycoside gives more RAPID KILLING - SYNERGY

true or false combination antimicrobial therapy can be used to prevent resistance

true

4 disadvantages of combination antimicrobial therapy

-superinfection risk -toxicities -antagonist -cost

when monitoring the therapeutic response to antibiotics, _____________ improvement may lag

radiologic

do we repeat chest x rays to check for therapeutic response improvement

NO - only if pt not improving

give 2 ab's where we do therapeutic drug monitoring

vancomycin or aminoglycosides

4 scenarios when we can do IV-PO switch

-overall clinical improvement -no fever for 24 hrs -decreased WBC -functioning GI tract

true or false IV to PO switch does not decrease infection rates

FALSE - it does there's no open IV line

1st 2nd and 3rd line for HOSPITAL ACQUIRED MRSA also, name how they come which has interaction with statin and can increase CPK (creatinine phosphokinase)

vancomycin (IV and PO, but PO only for c diff) linezolid (PO and IV) daptomycin (NOT FOR LUNGS) (IV only) dapto

what is the ONLY cephalosporin with MRSA coverage

Ceftaroline (5th gen)

name 3 main ABs mainly used for community acquired MRSA (not hospital)

bactrim clindamycin doxycycline

does ceftaroline have pseudomonas coverage

NO has MRSA coverage tho

"cousin" of linezolid that has less thrombocytopenia issues and no DDI with SSRIs

tedizolid

2 "cousins" of vanco that are very long acting glycopeptides (1-2 weeks)

dalbavancin oritavancin

true or false tigecyciline does not have MRSA coverage

FALSE - it does

fluoroquinolone not really used but has MRSA coverage and pseudomonas coverage

delafloxacin

differentiate between intrinsic and acquired resistance and give ex

intrinsic - vanco has always and will always be ineffective against gram negative, cephalosporins will never work against enterococcus acquired - due to inappropriate abx use (ie: decreased permeability, efflux pump, drug inactivation, altered target)

drug of choice for MRSA and 3 alternatives

vancomycin daptomycin, linezolid, and ceftaroline

what is VRE and explain it what are drugs of choice

vancomycin resistant enterococcus altered target site D-alanyl-D-alanine switched to D-alanyl-D-lactate linezolid and daptomycin are drugs of choice

what are ESBLs and what are the drugs of choice

extended spectrum beta lactamases - they hydrolyze the beta lactam ring and inactivate most beta lactams (penicillin, cephalosporin, and monobactam) CARBAPENEMS are drug of choice

ESBLs are produced by gram positive or negative bacteria

NEGATIVE

what are CREs

carbapenem resistant enterobacterales produce carbapenamases that inhibit ALL BETA LACTAMS - INCLUDING CARBAPENEMS

drugs of choice for CREs

tailored to whatever is most susceptible, but there's polymyxin, ceftazidime/avibactam, meropenem/vaborbactam (newer beta lactams)

primary and secondary goal of antimicrobial stewardship

primary - optimize clinical outcomes while minimizing unintendend consequences (c diff diarrhea, resistance) secondary - decrease healthcare costs

antimicrobial stewardship was a mandate made by _______-

the joint commission