Beta-Lactam Ab + Flashcards
what are the two major Ab that inhibit bacterial cell wall synthesis?
penicillins and cephalosporins
true or false: vancomycin, fosfomycin and bacitracin are all examples of beta-lactam drugs
false; they also inhibit cell wall synthesis but are NOT beta-lactam drugs
true or false: oral bioavailability of penicillins remains constant throughout the class
false: penicillins vary in their resistance to gastric acid and therefore vary in their bioavailability
tubular secretion of penicillins is inhibited by which drug?
probenecid - therefore increasing its concentration and prolonging its activity
true or false: most penicillins cross the BBB very easily.
false; most only cross when the meninges are inflamed
beta lactams work to inhibit cell wall synthesis by binding to specific enzymes called what? located where?
PBPs penicillin binding proteins; cytoplasmic membrane
penicillins also work to inhibit ____ which cross-link the linear peptidoglycan chains of the cell wall
transpeptidation reaction
why is it that drugs such as clavulanic acid, sulbactam, and tazobactam are often used in combination with penicillins ?
b/c they work as beta-lactamases inhibitors which can then prevent the inactivation of penicillin by penicillinases
what mechanism of resistance is responsible for MRSA and PRSP?
structural changes in PBPs; FYI: PRSP = penicillin resistant streptococcus pneumoniae
what is the mode of some gram-negative rods in terms of developing resistance to penicillins?
changes in porin structures in outer cell wall membrane may contribute to resistance by impeding access of penicillins to PBPs
what is the prototype of a subclass of penicillins that have a limited spectrum of antibacterial activity? (susceptible to beta-lactamases)
penicillin G
what is the DOC to treat syphilis?
penicillin G
which penicillin is an oral drug mainly used in oropharyngeal infections?
penicillin V
why is it that methicillin is so rarely used?
nephrotoxic potential
true or false: nafcillin and oxacillin are both penicillinase susceptible agents
false - penicillinase resistant, but NARROW spectrum
which two drugs are known to have a wider spectrum of antibacterial activity, but remains susceptible to penicillinase?
amoxicillin and ampicillin
true or false: piperacillin and ticarcillin are bother penicillinase resistant
false; susceptible and often used in combination with penicillinase inhibitors to enhance their activity
which penicillin is often associated with interstitial nephritis?
methicillin
which penicillin is associated with neutropenia?
nafcillin
what are the two most common results of penicillin toxicity?
allergy and GI disturbances (for the latter, especially with ampicillin)
true or false: most cephalosporins are administered orally
false; most are available for oral use, but most are administered parenterally
what is the major method of elimination for cephalosporins?
renal excretion via active tubular secretion
how is ceftriaxone mainly excreted?
in the bile
true or false: most 1st and 2nd generation cephalosporins enter the CSF
false; most do NOT enter the CSF even when the meninges is inflamed
true or false: cephalosporins are more susceptible to penicillinases produced by staph
false; structural changes make cephalosporins LESS susceptible
cefazolin and cephalexin are members of which class of antibiotics? (be specific)
first generation cephalosporins
which two drugs are currently the most active cephalosporins against penicillin-resistant pneumococci?
ceftriaxone and cefotaxime
what are the two cephalosporins that are currently the DOC for treatment of gonorrhrea?
ceftriaxone (parenteral) and cefixime (oral)
true or false: drugs of the 3rd generation cephalosporins class should typically be reserved to treat serious conditions
true
true or false: as cephalosporins increase in generation, coverage of gram + bacteria increase
false; decreases
what is the cephalosporin with activity against MRSA?
cefaroline
what is the name of the cephalosporin that combines gram + activity of 1st generation agents with the wider 3rd generation agents?
cefepime
true or false: cephalosporins cause more allergic reactions than does penicillins
false; far less
true or false: complete cross-hypersensitivity between different cephalosporins should be assumed.
true
true or false: cross-hypersensitivity between penicillins and cephalosporins is complete at approximately 65%
false; it is incomplete (5 to 10%) - this makes it such that penicillin-allergic pts can sometimes be treated successfully with a cephalosporin NOTE: pts with anaphylaxis to penicillin should NEVER be treated with cephalosporin
what is the possible result of drug-drug interaction between cephalosporins and aminoglycosides?
nephrotoxicity
when used in combination with cephalosporins, drugs containing a methylthiotetarzole group (ex: cefamandole) may cause what two major side effects?
hyPOprothrombinemia and disulfiram-like reactions with ethanol.
which beta-lactam drug am I? a monobactam; resistant to beta-lactameses; no activity against gram + bacteria or anaerobes; inhibitor of cell wall synthesis; binds specifically to PBP3
aztreonam
to which class of beta-lactam drugs do the following belong? imipenem, doripenem, meropenem, and ertapenem
carbapenems (chemically different from penicillins BUT have the beta lactam ring) Note: these drugs have a low susceptibility to beta-lactamases
with the exception of which drug are the carbapenems active against p aeruginosa and acinetobacter species?
ertapenem
carbapenems are often used in combination with what other drug when fighting pseudomonas infections?
aminoglycosides.
why is imipenem administered in fixed combination with cilastatin?
b/c it is inactivated by renal dydropeptidase I and cilastatin can inhibit this enzyme therefore increasing plasma half-life of imipenem. Note: imipenem also inhibits the formation of a potentially nephrotoxic metabolite by increasing the plasma half life.
at very high levels what is the most serious side effect of carbapenems?
that they cause CNS toxicity and can lead to confusion, encephalopathy and seizures
which drug am I? binds to D-Ala-D-Ala terminal of the nascent peptidoglycan pentapeptide side chain and inhibits transglycosylation (which prevents elongation of the peptidogylcan chain and interferes with cross-linking)
bacterial glycoprotein, vancomycin
what is the means of resistance for VRE and VRSA?
decreased affinity of vancomycin for the binding site b/c of the replacement of terminal D-Ala by D-lactate
what is the DOC for treatment of MRSA?
Vancomycin
what it the DOC for treatment of PRSP?
vancomycin in combination with 3rd generation cephalosporin
rapid intravenous infusion of vancomycin may cause “red man syndrome” - why is this?
the diffuse flushing (“red man syndrome”) is due to an influx of histamine release
what is a common example of an antimetabolite inhibitor of cytosolic enolpyruvate transferase ?
fosfomycin (its actions prevent the formation of N-acetylmuamic acid, which is an essential precursor molecule for peptidoglycan chain formation).
which drug am I? limited to topical use due to nephrotoxicity; peptide Ab; interfere with late stage of cell wall synthesis
bacitracin
which drug am I? only used to treat TB caused by organisms resistant to 1st line anti TB meds; antimetabolite that blocks the incorporation of D-Ala into the pentapeptide side chain of the peptidoglycan.
cycloserin
what levels should be monitored when a patient is on daptomycin?
creatinine phosphokinase since it can cause myopathy
