Beta-Lactams

Question 1

what does ADME stand for?

Answer 1

absorption/route
distribution
metabolism
excretion

Question 2

what are the mechanisms of action for beta-lactams?

Answer 2

inhibit cell wall synthesis
bactericidal

Question 3

how do beta-lactams inhibit cell wall synthesis?

Answer 3

bind to penicillin binding proteins and reduce cross linking of the peptidoglycan cell wall

Question 4

what is the most significant mechanism of acquired resistance?

Answer 4

production of beta-lactamases: acquired chromosomally or via plasmids/transposons

Question 5

what are the mechanisms of resistance to beta lactams?

Answer 5

production of beta-lactamases
alteration of penicillin-binding protein
crypticity (drug property)
altered PBP

Question 6

what is crypticity?

Answer 6

a drug property that contributes to resistance
ability to reach the site of action in gram negative bacteria

Question 7

the mecA gene codes for a different PBP- PBP2a that ______________________________________________

Answer 7

does not allow binding by any beta-lactam

Question 8

what type of mutation is the mecA gene that codes for a different PBP - PBP2a?

Answer 8

chromosomal

Question 9

true/false: time above MIC is more important that how far above the MIC is reached for beta lactams

Answer 9

true

Question 10

what is the most important adverse effect of beta lactams?

Answer 10

diarrhea/colic/disruption of fermentation
caution with use in hind gut fermenters

Question 11

penicillin G is _____-labile

Answer 11

acid

Question 12

who should you not use penicillin G in?

Answer 12

guinea pigs
caution in rabbits and chinchillas

Question 13

what are the two main formulations of penicillin G?

Answer 13

crystalline
procain penicillin G: not IV

Question 14

does penicillin G work on E coli?

Answer 14

no

Question 15

does penicillin work on gram positives or gram negatives in general?

Answer 15

gram positives

Question 16

what are some microbes that penicillin G works well for?

Answer 16

Streptococcus
anaerobes

Question 17

what is a gram negative microbe that penicillin G works for?

Answer 17

Leptospirosis

Question 18

what does increased crypticity of broad spectrum penicillins allow?

Answer 18

better penetration of gram-negative bacteria

Question 19

can broad spectrum penicillins be given orally?

Answer 19

yes- acid stable
amoxicillin more bioavailable that ampicillin and is recommended for oral therapy (dogs and cats)

Question 20

what is Polyflex?

Answer 20

ampicillin trihydrate

Question 21

what is important about extended spectrum penicillins (with gram negatives)?

Answer 21

further increased crypticity and able to bind altered penicillin binding proteins
significant gram negative activity extending to Pseudomonas

Question 22

which pathogens can extended spectrum penicillins work against?

Answer 22

E. coli
Streptococcus
anaerobe
Leptospirosis
Pseudomonas

Question 23

what is done to potentiated penicillins?

Answer 23

penicillinase inhibitor is added to the formulation to “release” the penicillin: clavulanic acid, sulbactam

Question 24

potentiated penicillins only work in those bacteria resistant by virtue of __________________, not with altered penicillin binding protein

Answer 24

penicillinase

Question 25

how effective is amoxicillin-clavulanate against the four quadrants, and one more?

Answer 25

E. colo in urine, maybe not in tissue Staphylococcus: ++ Streptococcus: + anaerobe: + Bacteroides fragilis: +

Question 26

do amoxicillin-clavulanate or piperacillin-tazobactam work against Rickettsia or Mycoplasma?

Answer 26

no

Question 27

what drug is effective against Leptospirosis and Pseudomonas?

Answer 27

piperacillin-tazobactam

Question 28

what is the structural feature of beta lactams that is a target for drug resistance?

Answer 28

beta lactam ring

Question 29

what is the distribution of beta lactams?

Answer 29

mostly extracellular third generation cephalosporins and carbapenems are an exception to limited distribution and penetrate all tissue (including blood brain barrier)

Question 30

what is the metabolism of beta lactams?

Answer 30

limited

Question 31

how are beta lactams excreted?

Answer 31

renal filtration and excretion concentrate in urine which can help their effectiveness with UTIs

Question 32

how are beta lactams bactericidal?

Answer 32

create osmotic imbalance between hypertonic bacterial interior and isotonic exterior: cell lysis

Question 33

how do beta lactams inhibit cell wall synthesis?

Answer 33

bind to penicillin binding proteins and reduce cross linking of the petidoglycan wall

Question 34

how does altered PBP contribute to resistance of beta lactams?

Answer 34

mecA gene codes for a different PBP: PBP2a PBP2a does not allow binding of any beta lactam

Question 35

what type of mutation is the mecA gene?

Answer 35

chromosomal

Question 36

what does the mecA gene mutation imply resistance to?

Answer 36

almost all beta lactams including carbapenems

Question 37

why are there different targets for necessary time above MIC with beta lactams?

Answer 37

depending on drug and agent due to post-antibiotic effect

Question 38

what is added to beta lactams to increase their effect (broad and extended spectrums)?

Answer 38

beta lactamase inhibitor

Question 39

can you give procain penicillin IV?

Answer 39

no

Question 40

what is the spectrum of Penicillin G with the 4 quadrants?

Answer 40

E coli: - Staphylococcus: * Streptococcus: + anaerobe: +

Question 41

what are some broad spectrum penicillins?

Answer 41

aminopenicillins: ampicillin and amoxicillin

Question 42

is amoxicillin or ampicillin more bioavailable and recommended for oral therapy?

Answer 42

amoxicillin

Question 43

how can ampicillin trihydrate be given?

Answer 43

IM or SQ

Question 44

what is the efficacy of ampicillin and amoxicillin against the four quadrants?

Answer 44

E coli: +/- Staphylococcus: * Streptococcus: + anaerobe: +

Question 45

what is one pathogen that ampicillin and amoxicillin are effective against that is not in the four quadrants?

Answer 45

Leptospirosis

Question 46

what is the efficacy of piperacillin (extended spectrum penicillins) against the four quadrants?

Answer 46

E coli: ++ Staphylococcus: * Streptococcus: + anaerobe: +

Question 47

what are the potentiateed penicillin formulations?

Answer 47

oral amoxicillin + clavulanic acid: clavamox or augmentin (human) injectable ampicillin + sulbactam: unasyn (human)