Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

ID Week 3 > ICL 2.28: Antibiotics III > Flashcards

ICL 2.28: Antibiotics III Flashcards

(63 cards)

Start Studying
1
Q

what do β-lactamases do?

A

these enzymes hydrolyze the β-lactam ring, deactivating the drug, but are not covalently bound to the drug as PBPs are

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

where are β-lactamases found?

A

they are especially prevalent in Gram (-) bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how many classes of β-lactamases are there? how do they work?

A

A,C,D = catalyze the reaction using a serine residue

B class = uses metallo- β-lactamases to catalyze the reaction using zinc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what two categories of β-lactamases are there?

A
  1. chromosomal borne

expression of chromosomal b-lactamases can be induced by β-lactam antibiotics

  1. plasmid borne

plasmids bearing β-lactamases can be transmitted across bacterial species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the most commonly encountered β-lactamase in gram - bacteria?

A

TEM-1

it’s a plasmid-mediated β-lactamase

up to 90% of ampicillin resistance in E. coli is due to the production of TEM-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the classes of β-lactamases?

A
  1. penicillinases
  2. cephalosporinases/carbapenemases
  3. extended spectrum β-lactamase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are penicillinases?

A

β-lactamase that only hydrolyze β-lactam ring in penicillins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are cephalosporinases/carbapenemases?

A

B-lactamases that preferentially cleave these β-lactams

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are extended spectrum β-lactamases?

A

β-lactamases that cleave penicillins, cephalosporins, and sometimes also carbapenems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the 3 β-lactamases inhibitor drugs available?

A
  1. clavulanate
  2. sulbactam
  3. tazobactam

these are the 3 currently clinically available β-lactamases inhibitors which are combined with β-lactam antibiotics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what do β-lactamases inhibitors do?

A

they bind irreversibly to β-lactamases but do not have good activity against PBPs

their rings are modified to break open after acylating the β-lactamase enzyme

so they inactivate bacterial β-lactamases and are used to enhance the antibacterial actions of β-lactamases antibiotics

but they only have weak antibacterial actions…

they inhibit many but not all bacterial β-lactamases and can protect hydrolyzable penicillins from inactivation by the enzymes

they are only available in fixed combination with specific penicillins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is Unasyn?

A

β-Lactam/inhibitor combination:

ampicillin + sulbactam

ampicillin is an aminopenicillin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is augmentin?

A

β-Lactam/inhibitor combination:

amoxicillin + clavulanate

amoxicillin is an aminopenicillin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is zosyn?

A

β-Lactam/inhibitor combination:

piperacillin + tazobactam

piperacillin is a ureidopenicillin extended-spectrum penicillin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is timentin?

A

β-Lactam/inhibitor combination:

ticarcillin + clavulanate

ticarcillin is carboxypenicillin extended-spectrum penicillin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how do β-Lactam/inhibitor combinations work?

A

the companion penicillin, not the β-lactamase inhibitor, determines the antibacterial spectrum of the combination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the structure of cephalosporins?

A

cephalosporins are similar to penicillins but have a 6 member dihydrothiazine ring instead of a 5 member thiazolidine ring

unlike penicillin, cephalosporins have two side chains which can be easily modified
cephalosporins are also more difficult for β-lactamases to hydrolyze

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

structure of cephalosporins

A

slide 15

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what happens when you make substitutions at cephalosporin ring position 7?

A

substitutions at cephalosporin ring position 7 affect spectrum and stability to β-lactamases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what happens when you make substitutions at cephalosporin ring position 3?

A

substitutions at ring position 3 influence the pharmacokinetic profile and toxicity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what does an additional CD3O- attached to ring position 7 do to cephalosporins?

A

cephamycins that have an additional CH3O- attached to ring position 7

they are even more resistant to β-lactamases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the mechanism behind cephalosporins?

A

the acetoxy group (or other R group) will leave when the drug acylates the PBP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the 1st generation parenteral and oral cephalopsorin drugs?

A

PARENTERAL

  1. cefazolin
  2. cephalothin

ORAL
1. cephalexin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are the 2nd generation parenteral and oral cephalopsorin drugs?

A

PERENTERAL
1. cefotetan

ORAL
1. cefprozil

  1. cefuroxime-axetil
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
what are the 3rd generation parenteral and oral cephalopsorin drugs?
PARENTERAL 1. cefotaxime 2. ceftazidime 3. ceftriaxone ORAL 1. cefdinir
26
what are the 4th generation parenteral and oral cephalopsorin drugs?
PARENTERAL | 1. cefepime
27
how are cephalosporins classified?
cephalosporins are classified into generations based on their activity later generations generally become more effective against Gram (-) bacteria due to an increasing number of polar groups (also become zwitterions) later generations are often the broadest spectrum and are reserved against penicillin resistant infections to prevent the spread of cephalosporin resistant bacteria
28
which cephalosporin can cross the blood brain carrier? what's it used to treat?
Ceftazidime (3rd gen) it can can cross the blood brain barrier so it's used to treat meningitis
29
what are the characteristics of first generation cephalosprins?
they have a stronger antimicrobial action on G+ bacteria than the other generations, but action on G- bacteria is relatively poor
30
what do first generation cephalosporins not work on?
they are NOT effective against Pseudomonas
31
what are first generation cephalosporins used to treat?
they are chiefly used in treating infection of the penicillinase-producing aurococcus (S. aureus) and as surgical prophylaxis most commonly used 1st Gen is Cephalexin
32
what are the characterisitcs of cefazolin?
parenteral 1st generatio cephalosporin drug is cleared by glomerular filtration and is highly protein bound consequently, it has a relatively long plasma half-life (~2hrs) does not penetrate CNS and can not be used to treat meningitis
33
what are the characteristics of second generation cephalosporins?
action of this generation on G+ bacteria is the same or a little less than that of the first generation but their antimicrobial action on G- bacteria is increased
34
what is Cefotetan used to treat?
parenteral 2nd generation cephalosporin drug most effective against anaerobes such as B. fragilis
35
what do 2nd generation cephalosporin drugs not work on?
ineffective against Pseudomonas aeruginosa
36
what is cefuroxime used for?
oral 2nd generation cephalosporin it's the only second-generation drug that crosses the blood-brain barrier well enough to be used for the treatment of meningitis, especially H. influenzae meningitis Cefuroxime has enhanced activity against H. influenzae and M. catarrhalis respiratory infections, including B-lactamase expressing strains
37
what are the characteristics of 3rd generation cephalosporins?
the broadest spectrums of all cephalosporins high activity against G- bacteria high resistance to β-lactamases the best penetration into the CSF
38
what are 3rd generation cephalosporins mainly used for?
they are chiefly used in infections of the urethral or biliary tract with the drug-resistant strains and Pseudomonas
39
what is ceftazidime used for?
parenteral 3rd generation cephalosporin drug best activity of all cephalosporins against Pseudomonas (plus aminoglycoside for pseudomonal meningitis)
40
what is cefoperazone used for?
3rd generation cephalosporin drug it's eliminated (70%) in the bile, and is thus very useful in patients with renal failure
41
what is ceftriaxone used for?
parenteral 3rd generation cephalosporin drug drug of choice for treatment of gonorrhea also effective against many other gram - pathogens cleared by biliary excretion; relatively long plasma t1/2 (8 hours)
42
what is cefdinir used for?
oral 3rd generation cephalosporin drug caused by b-lactamase producing organisms
43
what are the characteristics of cefepime?
parenteral 4th generation cephalosporin drug stable to hydrolysis by plasmid-encoded B-lactamases unlike other cephalosporins, poor inducer of chromosomal B-lactamases, and some extended-spectrum plasmid encoded B-lactamases also relatively resistant to most of these B-lactamases NOT stable to some extended spectrum b-lactamases (e.g., TEM-3)
44
what other drug complication would indicate that you shouldn't use caphalosporin?
there is an approximately 10% incidence of cross-hypersensitivity between penicillins and cephalosporins cephalosporins are generally too risky for use in patients who have had an anaphylactic episode with a penicillin
45
what is an adverse effects of cephalosporin?
1. nephrotoxicity first-generation cephalosporins have certain nephrotoxicity second-generation have slight nephrotoxicity third and fourth generations have almost no nephrotoxicity
46
what is an adverse effect of cefotetan?
1. delayed blood clotting because of low prothrombin levels in blood 2. alcohol intolerance
47
what are carbapenems?
carbapenems are a potent class of β-lactams which attack a wide range of PBPs, have low toxicity, and are much more resistant to β-lactamases than the penicillins or cephalosporins
48
what is thienamycin?
carbapenem one of the most broad spectrum antibiotics ever discovered it uses import porins unavailable to other β-lactams to enter Gram (-) bacteria no cross-resistance with other b-lactams, and they are not recognized well by bacterial b-lactamases
49
how is thienamycin made?
due to its highly unstable nature this drug and its derivatives are created through synthesis, not bacterial fermentation
50
what do you have to give with thienamycin and why?
due to its rapid degradation by the renal peptidase, it is treated with cilastatin
51
which carbapenems are better than thienamycin?
modifications of Thienamycin have produced superior carbapenems called Meropenem and Ertapenem they are not degraded by renal peptidase and do not have the side effects of Imipenem
52
what is Cilastatin?
Cilastatin inhibits renal dehydropeptidase-1, an enzyme that inactivates imipenem Cilastatin also helps prevent kidney toxicity of imipenem by blocking its active uptake and accumulation by renal tubule cells that's why you give cilastatin with imipenem (thienamycin)
53
what is the most adverse effect of imipenem-cilastatin?
CNS toxicity there is decreased consciousness and myoclonic jerking this may result from cilastatin inhibition of imipenem transport out of the CSF
54
what is meropenem?
antimicrobial spectrum is broad, like imipenem but it's not hydrolyzed by dehydropeptidase-1 so there's decreased incidence of CNS toxicity compared with imipenem/cilastatin
55
what is the only clinically useful monobactam?
aztreonam
56
how does aztreonam work?
it's a monobactam while it resembles the other β-lactam antibiotics and targets the PBP of bacteria, its mechanism of action is significantly different it binds to PBP-3 which is ONLY present in aerobic Gram negative bacteria!!!! it's is highly effective in treating Gram (-) bacteria and is resistant to many β-lactamases and and does not induce expression of chromosomal b-lactamases if chromosomal B-lactamases have been induced by other B-lactams, they will bind aztreonam and prevent it from binding to PBP-3 little risk of cross-allergy with penicillins or cephalosporins (except ceftazidime)
57
which agents are primarily used as B-lactam substitutes?
1. spectinomycin 2. vancomycin 3. daptomycin
58
what is spectinomycin?
B-lactam substitue its sole use is for treatment of penicillin-resistant gonococcal infections or gonococcal infections in penicillin-allergic patients  does not penetrate the CNS low toxicity: nausea, chills, fever, dizziness
59
what is vacomycin?
B-lactam substitute used for treatment of meth.-resistant Staph. aureus (MRSA) it's also the backup drug for C. difficile pseudomembranous colitis but little activity vs Gm- bacilli
60
what is the MOA of vancomycin?
it's not a B-lactam!! Vancomycins bind to the two terminal amino acids of the monomer's pentapeptide (D-Ala-D-Ala) this binding prevents the transpeptidase enzymes from forming the peptide cross-links between the rows and layers of peptidoglycan
61
what are the adverse effects of vancomycin?
1. ototoxic = deafness 2. nephrotoxic = blood and protein in urine 3. thrombophlebitis = clots in bloodstream 4. hypotensioni & "red man" syndrome because the drug releases hsitamine
62
what is daptomycin?
B-lactam substitute a cyclic lipopeptide antibiotic inserts in cell membrane and causes rapid depolarization indicated for skin and skin structure infections also indicated for Staph. aureus bacteremia and endocarditis NOT effective for respiratory infections because daptomycin is inactivated by lung surfactant
63
what are the adverse effects of daptomycin?
significant muscle damage and muscle cell death = rhabdomyolysis so you need to monitor patients for muscle pain/weakness there can also be paresthesia at high doses = sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect

ID Week 3 (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions