Beta-Lactam Ab +

Question 1

what are the two major Ab that inhibit bacterial cell wall synthesis?

Answer 1

penicillins and cephalosporins

Question 2

true or false: vancomycin, fosfomycin and bacitracin are all examples of beta-lactam drugs

Answer 2

false; they also inhibit cell wall synthesis but are NOT beta-lactam drugs

Question 3

true or false: oral bioavailability of penicillins remains constant throughout the class

Answer 3

false: penicillins vary in their resistance to gastric acid and therefore vary in their bioavailability

Question 4

tubular secretion of penicillins is inhibited by which drug?

Answer 4

probenecid - therefore increasing its concentration and prolonging its activity

Question 5

true or false: most penicillins cross the BBB very easily.

Answer 5

false; most only cross when the meninges are inflamed

Question 6

beta lactams work to inhibit cell wall synthesis by binding to specific enzymes called what? located where?

Answer 6

PBPs penicillin binding proteins; cytoplasmic membrane

Question 7

penicillins also work to inhibit ____ which cross-link the linear peptidoglycan chains of the cell wall

Answer 7

transpeptidation reaction

Question 8

why is it that drugs such as clavulanic acid, sulbactam, and tazobactam are often used in combination with penicillins ?

Answer 8

b/c they work as beta-lactamases inhibitors which can then prevent the inactivation of penicillin by penicillinases

Question 9

what mechanism of resistance is responsible for MRSA and PRSP?

Answer 9

structural changes in PBPs; FYI: PRSP = penicillin resistant streptococcus pneumoniae

Question 10

what is the mode of some gram-negative rods in terms of developing resistance to penicillins?

Answer 10

changes in porin structures in outer cell wall membrane may contribute to resistance by impeding access of penicillins to PBPs

Question 11

what is the prototype of a subclass of penicillins that have a limited spectrum of antibacterial activity? (susceptible to beta-lactamases)

Answer 11

penicillin G

Question 12

what is the DOC to treat syphilis?

Answer 12

penicillin G

Question 13

which penicillin is an oral drug mainly used in oropharyngeal infections?

Answer 13

penicillin V

Question 14

why is it that methicillin is so rarely used?

Answer 14

nephrotoxic potential

Question 15

true or false: nafcillin and oxacillin are both penicillinase susceptible agents

Answer 15

false - penicillinase resistant, but NARROW spectrum

Question 16

which two drugs are known to have a wider spectrum of antibacterial activity, but remains susceptible to penicillinase?

Answer 16

amoxicillin and ampicillin

Question 17

true or false: piperacillin and ticarcillin are bother penicillinase resistant

Answer 17

false; susceptible and often used in combination with penicillinase inhibitors to enhance their activity

Question 18

which penicillin is often associated with interstitial nephritis?

Answer 18

methicillin

Question 19

which penicillin is associated with neutropenia?

Answer 19

nafcillin

Question 20

what are the two most common results of penicillin toxicity?

Answer 20

allergy and GI disturbances (for the latter, especially with ampicillin)

Question 21

true or false: most cephalosporins are administered orally

Answer 21

false; most are available for oral use, but most are administered parenterally

Question 22

what is the major method of elimination for cephalosporins?

Answer 22

renal excretion via active tubular secretion

Question 23

how is ceftriaxone mainly excreted?

Answer 23

in the bile

Question 24

true or false: most 1st and 2nd generation cephalosporins enter the CSF

Answer 24

false; most do NOT enter the CSF even when the meninges is inflamed

Question 25

true or false: cephalosporins are more susceptible to penicillinases produced by staph

Answer 25

false; structural changes make cephalosporins LESS susceptible

Question 26

cefazolin and cephalexin are members of which class of antibiotics? (be specific)

Answer 26

first generation cephalosporins

Question 27

which two drugs are currently the most active cephalosporins against penicillin-resistant pneumococci?

Answer 27

ceftriaxone and cefotaxime

Question 28

what are the two cephalosporins that are currently the DOC for treatment of gonorrhrea?

Answer 28

ceftriaxone (parenteral) and cefixime (oral)

Question 29

true or false: drugs of the 3rd generation cephalosporins class should typically be reserved to treat serious conditions

Answer 29

true

Question 30

true or false: as cephalosporins increase in generation, coverage of gram + bacteria increase

Answer 30

false; decreases

Question 31

what is the cephalosporin with activity against MRSA?

Answer 31

cefaroline

Question 32

what is the name of the cephalosporin that combines gram + activity of 1st generation agents with the wider 3rd generation agents?

Answer 32

cefepime

Question 33

true or false: cephalosporins cause more allergic reactions than does penicillins

Answer 33

false; far less

Question 34

true or false: complete cross-hypersensitivity between different cephalosporins should be assumed.

Answer 34

true

Question 35

true or false: cross-hypersensitivity between penicillins and cephalosporins is complete at approximately 65%

Answer 35

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

Question 36

what is the possible result of drug-drug interaction between cephalosporins and aminoglycosides?

Answer 36

nephrotoxicity

Question 37

when used in combination with cephalosporins, drugs containing a methylthiotetarzole group (ex: cefamandole) may cause what two major side effects?

Answer 37

hyPOprothrombinemia and disulfiram-like reactions with ethanol.

Question 38

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

Answer 38

aztreonam

Question 39

to which class of beta-lactam drugs do the following belong? imipenem, doripenem, meropenem, and ertapenem

Answer 39

carbapenems (chemically different from penicillins BUT have the beta lactam ring) Note: these drugs have a low susceptibility to beta-lactamases

Question 40

with the exception of which drug are the carbapenems active against p aeruginosa and acinetobacter species?

Answer 40

ertapenem

Question 41

carbapenems are often used in combination with what other drug when fighting pseudomonas infections?

Answer 41

aminoglycosides.

Question 42

why is imipenem administered in fixed combination with cilastatin?

Answer 42

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.

Question 43

at very high levels what is the most serious side effect of carbapenems?

Answer 43

that they cause CNS toxicity and can lead to confusion, encephalopathy and seizures

Question 44

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)

Answer 44

bacterial glycoprotein, vancomycin

Question 45

what is the means of resistance for VRE and VRSA?

Answer 45

decreased affinity of vancomycin for the binding site b/c of the replacement of terminal D-Ala by D-lactate

Question 46

what is the DOC for treatment of MRSA?

Answer 46

Vancomycin

Question 47

what it the DOC for treatment of PRSP?

Answer 47

vancomycin in combination with 3rd generation cephalosporin

Question 48

rapid intravenous infusion of vancomycin may cause "red man syndrome" - why is this?

Answer 48

the diffuse flushing ("red man syndrome") is due to an influx of histamine release

Question 49

what is a common example of an antimetabolite inhibitor of cytosolic enolpyruvate transferase ?

Answer 49

fosfomycin (its actions prevent the formation of N-acetylmuamic acid, which is an essential precursor molecule for peptidoglycan chain formation).

Question 50

which drug am I? limited to topical use due to nephrotoxicity; peptide Ab; interfere with late stage of cell wall synthesis

Answer 50

bacitracin

Question 51

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.

Answer 51

cycloserin

Question 52

what levels should be monitored when a patient is on daptomycin?

Answer 52

creatinine phosphokinase since it can cause myopathy