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Tony's lectures > Antibiotics 2 > Flashcards

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
Q

what is clavulanic acid?

A
  • it is a suicide of b-lactamases
26
Q

How does clavulanic acid inactive b-lacatmases?

A
  • bonds covalently to the lactamase enzyme
27
Q

clavulanic acid is combined with amoxycillin to form aygmetin. true or flase?

28
Q

what si the difference between the structure of penicillin and cephalosporin?

A
  • Cephalosporin has dihydrothiazine ring
29
Q

what bacteria is cephalosporin C active against?

A
  • Gram postive and gram negtaive but with low potency
30
Q

What are the issues with cephalosporin C?

A
  • Not orally active

- difficult ot isolate and purify

31
Q

cephalosporin C is not stable to acid and b-lactamases. true or flase?

32
Q

what is the mode of action for cephalosporin C?

A
  • PBP catalyses release of D-Ala from pentapeptide
33
Q

semi-synthetic derivartives of cephalosporin C are developed in generations. true or false?

34
Q

cephalosporin derivatives has a broader spectrum than penicillin. true or flase?

35
Q

cephalosporin derivatives not effective against many strains of bacteria. true or falase?

36
Q

cephalosporin are more expensive to produce and are onlu for hospital use. true or false?

37
Q

what are the positive propertiesof 1st generation cephalosporins?

A
  • 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
Q

Generally lower activity than comparable penicillins. treu or false?

39
Q

1st generation cephalosporin are generally poorly absorbed across the gut wall except what?

A
  • 3-methylsubstituted cephalosporins
40
Q

hwo are most 1st generation cephalosporins administered?

A
  • As injections
41
Q

resistnace has appeared with gram negative bacteria. true or false?

42
Q

Name some 1st generation cephalosporins?

A
  • Cephalothin

- Cephalexin

43
Q

Cephalothin is more active than Pen G agaist grame negtaive bacteria. true or false?

44
Q

cephalothin is more lilely to cause allergies. true or false?

45
Q

cephalothin is useful aginst penicillinase producing strains of S.aureus. true or false?

46
Q

cephalothin is poorly absorbed from GIT and is adminsitered by injection. true or false?

47
Q

3-hydroxymethyl metabolite is less active. true or false?

48
Q

what group in cephalexin is not good for activity?

A
  • Methyl group
49
Q

The methyl group in cephalexin aids in orall activity and absorption through the GIT. true or false?

50
Q

cephalexin has greater activity against gram negative bacteria. true or false?

51
Q

provide example of second generation cephalosporins?

A
  • Cefoxitin and cefuroxime
52
Q

Cefoxitin has Broader spectrum of activity and greater resistance to lactamase enzymes than most 1stgeneration cephalosporins. true or flase?

53
Q

which group in cefoxitin can act as a steric shield?

A

The 7-methoxy group may act as a steric shield

54
Q

the Urethane group is stable to metabolism in cefoxitin. true or flase?

55
Q

what happens when a methoxy group is introduced in position 6 of cefoxitin?

A

it eliminates activity

56
Q

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

57
Q

the Aminothiazole ring in 3rd generation cephalosporins enhances penetration of cephalosporins across the outer membrane of Gram -ve bacteria. true or false?

58
Q

3rd generation cephalosporins Lack activity against MRSA. true or false?

59
Q

hwo do Carbapenems work?

A

Bind to PBP2 to cause cell lysis

60
Q

what are some propeties of carbapenems?

A
  • Highly resistant to b-lactamases
  • Poor acid stability, much less that Penicillin G, and solutions are not stable
  • Some allergic reactions observed
61
Q

Stereochemistry different to that in penicillinsand cephalosporins. true or flase?

Tony's lectures (8 decks)

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