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Antibiotics 2 Flashcards

1
Q

what are the components of pencillin structre?

A
  • Amide bond
  • Bicyclic structure
  • Stereochemistry
  • Lactam
  • free acid
  • Thiazolidine ring
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2
Q

How many types of PBPs (penicillin binding protein) do bacteria have?

A
  • 5 types
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3
Q

B-lactams acylate the cative site serine residue of PBPs to inhibit transpeptidation. TRUE OR FALSE?

A

TRUE

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4
Q

PBPs have differing affinities for B-lactams. true or flase?

A

true

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5
Q

How is optimum antibacterial effects achieved?

A
  • Through binding to multiple types of PBPs
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6
Q

how can resistance be mediated with PBPs?

A
  • Through mutated PBPs
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7
Q

what are the two modes of action of penicillin?

A
  • Transpeptidase cross linking - PBP catalyses release of D-Ala from pentapeptide
  • Penicillin inhibition - penicillin binds irreversibly to PBP enzyme
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8
Q

penicillin G is non-toxic. TRUE OR FALSE?

A

TRUE

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9
Q

what type of bacteria is pencillin G active against?

A
  • Gram negtaive

- Gram positive - but not broad spectrum

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10
Q

what are the drawbacks of penicillin G?

A
  • Allergies are observed
  • Not orally active
  • Acid sensitive
  • Destroyed by b-lactamases
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11
Q

B-lactam is extremely reactive, unlike tertiary amide. true or false?

A

true

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12
Q

why is penicillin G acid sensitive?

A
  • the acid catalysed ring is opened and relieves the ring strain imposed by fusing a 4-memebered ring to a 5-memebered ring
  • Participation from the side chain opens the lactam
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13
Q

why is the side chain of pencillin V (5) unlikely to react with the b-lactam ring?

A
  • Due ot electronic effects
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14
Q

what are soem properties of pencillin V?

A
  • Acid stable
  • Can be taken orally, but now is sensitive to b-lactamases
  • Less potent than penicillin G
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15
Q

Resistance of b-lactamases is transferable between strains. treu ro false?

A

true

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16
Q

Gram negative bacteria do not have b-lactamases within the periplasmic space surrounding the cell. true or false?

A

true

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17
Q

how is lactamase resistance obtained?

A
  • They attach bulky groups that prevent access to the enzyme active site
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18
Q

Such b-lactamases resistant penicillin have little or no effect against gram negative bacteria. true or false?

A

true

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19
Q

what are B-lactamases?

A
  • they are enzymes produced by bacteria that provide multi-resistance to B-lactam antiiotics such as penicillin
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20
Q

Methicilin is resistant to b-lactamases, but is active sensitive so not orally active. true or flase?

A

true

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21
Q

what type of bacteria is methiciliin effective for?

A
  • weakly effective in gram positive

- But not effective in gram negative and MRSA

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22
Q

Between oxacillin, cloxacillin, Dicloxacillin and flucloxacillin, which has the highest bioavailability?

A
  • Flucloxacillin
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23
Q

oxacillin, cloxacillin, Dicloxacillin and flucloxacillin are stable to acid and b-lactamases. true ro false?

A

true

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24
Q

Give examples of broad/extended spectrum penicillins?

A
  • Ampicillin

- Amoxycillin

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25
what is clavulanic acid?
- it is a suicide of b-lactamases
26
How does clavulanic acid inactive b-lacatmases?
- bonds covalently to the lactamase enzyme
27
clavulanic acid is combined with amoxycillin to form aygmetin. true or flase?
true
28
what si the difference between the structure of penicillin and cephalosporin?
- Cephalosporin has dihydrothiazine ring
29
what bacteria is cephalosporin C active against?
- Gram postive and gram negtaive but with low potency
30
What are the issues with cephalosporin C?
- Not orally active | - difficult ot isolate and purify
31
cephalosporin C is not stable to acid and b-lactamases. true or flase?
false
32
what is the mode of action for cephalosporin C?
- PBP catalyses release of D-Ala from pentapeptide
33
semi-synthetic derivartives of cephalosporin C are developed in generations. true or false?
true
34
cephalosporin derivatives has a broader spectrum than penicillin. true or flase?
true
35
cephalosporin derivatives not effective against many strains of bacteria. true or falase?
false
36
cephalosporin are more expensive to produce and are onlu for hospital use. true or false?
true
37
what are the positive propertiesof 1st generation cephalosporins?
- Better range of activity than pencillins - Best activity against gram positive cocci - useful against some gram negative infections - Useful against S. aureus an step infcetions
38
Generally lower activity than comparable penicillins. treu or false?
true
39
1st generation cephalosporin are generally poorly absorbed across the gut wall except what?
- 3-methylsubstituted cephalosporins
40
hwo are most 1st generation cephalosporins administered?
- As injections
41
resistnace has appeared with gram negative bacteria. true or false?
true
42
Name some 1st generation cephalosporins?
- Cephalothin | - Cephalexin
43
Cephalothin is more active than Pen G agaist grame negtaive bacteria. true or false?
true
44
cephalothin is more lilely to cause allergies. true or false?
false
45
cephalothin is useful aginst penicillinase producing strains of S.aureus. true or false?
true
46
cephalothin is poorly absorbed from GIT and is adminsitered by injection. true or false?
true
47
3-hydroxymethyl metabolite is less active. true or false?
true
48
what group in cephalexin is not good for activity?
- Methyl group
49
The methyl group in cephalexin aids in orall activity and absorption through the GIT. true or false?
true
50
cephalexin has greater activity against gram negative bacteria. true or false?
true
51
provide example of second generation cephalosporins?
- Cefoxitin and cefuroxime
52
Cefoxitin has Broader spectrum of activity and greater resistance to lactamase enzymes than most 1stgeneration cephalosporins. true or flase?
true
53
which group in cefoxitin can act as a steric shield?
The 7-methoxy group may act as a steric shield
54
the Urethane group is stable to metabolism in cefoxitin. true or flase?
true
55
what happens when a methoxy group is introduced in position 6 of cefoxitin?
it eliminates activity
56
Resistant to esterases due to the urethane group•Wide spectrum of activity, including organisms that have gained resistance to penicillin•Used clinically against respiratory infections. true ro false? Cefuroxime
true
57
the Aminothiazole ring in 3rd generation cephalosporins enhances penetration of cephalosporins across the outer membrane of Gram -ve bacteria. true or false?
true
58
3rd generation cephalosporins Lack activity against MRSA. true or false?
true
59
hwo do Carbapenems work?
Bind to PBP2 to cause cell lysis
60
what are some propeties of carbapenems?
- Highly resistant to b-lactamases - Poor acid stability, much less that Penicillin G, and solutions are not stable - Some allergic reactions observed
61
Stereochemistry different to that in penicillinsand cephalosporins. true or flase?
true

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