antibiotics MT1 Flashcards
what are the 5 different ways that antibiotics work (mechanisms of action)
- inhibition of cell wall synthesis
- inhibition of protein synthesis
- inhibition of nucleic acid synthesis
- alteration of cell membrane function
- alteration of cell metabolism
a microbiology lab determines the _______ by mixing a standard concentration of the organisms that the patient has grown with increasing concentrations of the antibiotic in a broth solution. the mixture with the lowest concentration of antibiotic where there is no visible growth is deemed to be the ___________
MIC - minimun inhibitory concentration
is this susceptible, intermediate or resistant?
if the MIC < breakpoint, at typical doses the antibiotic would have a high probability of being effective
susceptible (S)
is this susceptible, intermediate or resistant?
if the MIC is approaching or near the determined breakpoint. the antibiotic may be effective at higher doses (if safely attainable)
intermediate (I)
is this susceptible, intermediate or resistant?
if the MIC is greater than the breakpoint the antibiotic would be unlikely to achieve therapeutic success
resistant (R)
what three classes of antibiotics are bacteriostatic?
- macrolides (azithromycin, clarithromycin, erythromycin)
- tetracyclines (doxycycline)
- linezolid
what are some mechanisms of resistance that bacteria can produce
- enzymatic destruction
- altered binding sites
- efflux pumps
- modified cell wall porins
what antibiotics are considered to be beta-lactams
penicillins (e.g. pen V/G, amoxicillin, cloxacillin)
cephalosporins (cephalexin, cefuroxime, cefixime)
carbapenems (imipenem, meropenem, ertapenem)
what are some examples of macrolides
erythromycin, clarithromycin, azithromycin
what are some examples of tetracyclines
tetracycline, doxycycline, minocycline
what are some examples of fluoroquinolones
ciprofloxacin, norfloxacin, levofloxacin, moxifloxacin
what are some examples of aminoglycosides
gentamicin and tobramycin
what is the mechanism of action of beta-lactams
beta-lactams bind to penicillin binding proteins (PBP) which cause the peptidoglycan barrier to not form properly causing cell lysis.
what is the most common mechanism of bacterial resistance in beta-lactams
enzymatic destruction and altered PBP sites
are beta-lactams bactericidal or bacteriostatic
bactericidal
are beta-lactams time dependant or concentration dependant
time dependant
what is the most common ADR for beta-lactams
hypersensitivity reaction
true/false: delayed rashes caused by penicillin, if after a few doses/days and NO itchiness/hives are typically indicative of a true IgE-mediated allergy
false - worried if rash happens right away with itchiness/hives
what should be done when patients have an uncertain penicillin allergy (such as reaction took place >10 years ago, or when reaction took places after days rather than hours when taking the antibiotic
refer patients for skin testing
if patient develops a rash with no itching/urticaria from penicillin, what other drug can be given?
a beta-lactam such as a cephalosporin can be given
this cephalosporin has a unique side chain to all other beta-lactams
cefalozolin
this beta-lactam is known for causing idiopathic skin rashes (maculopapular - not allergy associated)
amoxicillin
this beta-lactam seems to cause more hematologic issues
pip-tazo
this beta-lactam can bind to Ca (causing precipitation) and biliary slugging, mostly in paediatrics therefore should not use together with IV Ca
Ceftriaxone
this beta-lactam can cause seizure in renal dysfunction
cefepime
what pencillins must be taken on an empty stomach
Pen V and cloxacillin
all of the oral cephalosporins have excellent oral absorption except these two
cefixime and cefuroxime
this type of bacteria produces beta-lactamases, therefore the primary pencillins (pen V and pen G) did not have coverage for them. Cloxacillin was then introduced to help cover this type of bacteria
staph aureus
true/false: cloxacillin has strep coverage
true - not DOC but cloxacillin is active against strep spp.
these bind to beta-lactamase enzymes and therefore restore any susceptibility that was lost due to bacterial development of beta-lactamases (e.g. staph aureus, h. influenza, moxarella) and bacteria that always intrinsically produced beta-lactamases (e.g. b. frag)
beta-lactamase inhibitors (e.g. clavulin, tazobactam)
this penicillin medication was introduced to help cover gram -ve bacteria. it has a longer side chain which allows it to bind to different sites (PBP) and therefore has better gram negative coverage including some Pseudomonas spp.
piperacillin/tazobactam
true/false: as you go up in generations of cephalosporins, you get more gram -ve coverage
true
what are examples of first generation cephalosporins
cefadroxil, cephalexin, cefazolin
“CEFA”
what pneumonic can be used to remember the gram -ve coverage for first gen cephalosporins
PEK
P-proteus spp.
E- e.coli (not ESBLs)
K-Klebsiella (not ESBLs)
what are some examples of second generation cephalosporins
cefuroxime, cefprozil, cefoxitin
what pneumonic can be used to remember the gram -ve coverage for second gen cephalosporins
HPEK
H- H.influenzae (and M. catarrhalis)
P-proteus spp.
E- e.coli (not ESBLs)
K-Klebsiella (not ESBLs)
what are examples of third generation cephalosporins
cefixime, cefotaxime, ceftriaxone, ceftazidime
“ends in one or me”
what pneumonic can be used to remember the gram -ve coverage for third gen cephalosporins
HENPEK
H - H.influenzae
E- enterobacter spp.
N- N. meningiditis
P-proteus spp.
E- e.coli (not ESBLs)
K-Klebsiella (not ESBLs)
this third generation cephalosporin has very poor activity against gram positive bacteria.
cefatazidime
What are some examples of fourth generation cephalosporins
Ceftobiprole and cefepime
What are examples of fifth generation cephalosporins
Ceftolozone/tazobactam
If you over treat with this second generation cephalosporin, it will cause an influx of beta-lactamases
Cefoxitin (IV)
these are structurally more resistant to beta-lactamases. has a major toxicity of seizures.
Carbapenems (e.g. imipenem, meropenem, ertapenem)
true/false: all carbapenems are DOC for e.coli, klebsiella (non-ESBLs) and B.frag
false - covers ESBLS!!
what is the MOA for macrolides
bind to the 50S subunit and inhibits protein synthesis
what is the MOR for macrolides
europe - alteration of ribosomal binding site
North America - reduced permeability of cell membrane/reflux
true or false: macrolides have a prolonged antibiotic effect (PAE)
true
are macrolides time or concentration dependant
time (azithromycin is conc. dependant DAAMQ)
are macrolides bacteriostatic or cidal
bacteriostatic
this macrolide should be taken on an empty stomach
erythromycin
what are some ADRs of macrolides
- taste disturbances
- Qt prolongation
this tetracycline is similar to erythromycin and Pen G/V in that it is the first tetracycline and therefore has the least antimicrobial spectra of the tetracyclines.
tetracycline
what is the MOA of tetracyclines
binds to 30S ribosomal subunit therefore inhibits protein synthesis
what is the MOR for tetracyclines
decreased intracellular accumulation due to efflux by bacteria protein pump
are tetracyclines bacteriostatic or cidal
static (in MTL)
are tetracyclines time dependant or concentration dependant
time dependant
true or false: tetracyclines have prolonged antibiotic effects
true
which tetracycline should be taken on an empty stomach
tetracycline
what are the most common ADRs for tetracyclines
- photosensitivity
- avoid with divalent cations
- esophageal ulceration
- baby teeth may turn gray
__________ is LEAST likely to cause C. diff infection
tetracyclines
this class of antibiotics are the opposite of the beta-lactams in that they started out with great gram -ve coverage but not great gram +ve.
fluorquinolones
what is the MOA of fluoroquinolones
DNA! blocks bacterial DNA synthesis by inhibiting bacterial topoisomerase II (DNA gyrase and IV
what is the MOR of fluoroquinolones
alterations in DNA gyrase making it difficult for a fluoroquinolone to bind
are fluoroquinolones bacteriostatic or cidal
cidal
are fluoroquinolones concentration or time dependant
concentration
what fluoroquinolones need to be really adjusted
levo and cipro NOT MOXI
what are ADRs in fluoroquinolones
- can affect sugars
- QT prolongation
- photosensitivity
- drowsiness
- confusion
- tendinopathy
what are examples of ahminoglycosides
gentamicin and tobramycin
what is the MOA of ahminoglycosides
binds to 30S ribosomal subunit and results in a defective cell membrane
true or false: ahminoglycosides have a significant post-antibiotic effect (PAE)
true
what are some ADRs of aminoglycosides
- nephrotoxicity
- ototoxicity
- neuromuscular blockade
true or false: aminoglycosides only cover gram +ve bacteria
false - only gram negative
what is the MOA of vancomycin?
inhibits cell wall synthesis and the cell membrane is also damaged
true or false: vancomycin is used IV to treat C. diff
false - used po to treat C diff as it stays in the GI tract and stays in contact with the C.diff
what is the MOR for vancomycin
it binds to the extra peptidoglycan layers which are dead binding sites and therefore cannot reach the site of action
true or false: vancomycin essentially only covers gram +ve
true
true or false: vancomycin should only be used when a bacteria is resistant to other antibiotics or other antibiotics cannot be used due to ADRs or allergies
true
what are some ADRs of vancomycin
- infusion reactions
- otoxicity
- nephrotoxicity
what is the MOA of clindamycin
binds to the 50S ribosomal subunit, inhibiting protein synthesis
what is the MOR of clindamycin
- mutation of the ribosomal receptor site
- modification of the receptor
- enzymatic inactivation of clindamycin
is clindamycin bacteriostatic or cidal
static
what is one main ADR of clindamycin
diarrhea!! probably the worst for causing C. diff
this inhibits bacteria synthesis of dihrdyofolic acid by competition with para-amino benzoic acid
sulfamethoxazole
this blocks the production of THF acid from dihyrofolic acid by reversibility inhibiting the requires enzyme dihydrofolate reductase
trimethoprim
is TMP-SMX bacteriostatic or cidal
each are static on their own but cidal together
is TMP-SMX concentration or time dependant
time
what are some ADRs of TMP-SMX
- SJS/TEN
-avoid in pregnancy
N/V/D
this medication has an MOA of altering bacterial ribosomal proteins which inhibits synthesis of DNA, RNA and proteins
nitrofurantoin
this medication is exclusively used for UTIs and should not be used if a CrCl of < 30 ml/min
nitrofurantoin
what are some ADRs of nitrofurantoin
darken urine
GI upset (take with food) `
this medication has an MOA of inhibiting cell wall synthesis. it also decreases the adherence of bacteria to the epithelial cells of the urinary tract
fosfomycin
what are some ADRs of fosfomycin
- headache
- diarrhea
- GI upset
- hypokalemia
this medication works by passive diffusion into the cytoplasm of anaerobic bacteria. results inhibition of DNA synthesis and degradation and ultimately bacterial death; it is used for anaerobic and parasitic infections
metronidazole
