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MT6314 (PCOL) > Beta-Lactam & Other Cell Wall- & Membrane-Active Antibiotics > Flashcards

Beta-Lactam & Other Cell Wall- & Membrane-Active Antibiotics Flashcards

1
Q

____________ share features of chemistry, mechanism of action, pharmacology, and immunologic characteristics with cephalosporins, monobactams, carbapenems, and β-lactamase inhibitors.

A

Penicillins

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2
Q

All beta-lactam compounds contain a ____________ containing an amide group, which reacts with the active site of enzymes involved in building the bacterial cell wall.

A

4 membered lactam ring

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3
Q

The basic chemical structure of all penicillins consists of a:

A
  • thiazolidine ring (attached to)
  • β-lactam ring
  • secondary amino group (6-aminopenicillanic acid)
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4
Q

____________ of the β-lactam ring by bacterial β-lactamases yields ____________, which lacks antibacterial activity

A

Hydrolysis
yields: penicilloic acid

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5
Q

True or False

The penicillins are susceptible to inactivation by amidases and lactamases

A

True

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6
Q

T or F

Carbapenems have a the same stereochemical configuration in the lactam ring that imparts resistance to most common β-lactamases.

A

F

different stereochemical configuration

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7
Q

Substituents of the ________________ determine the essential pharmacologic and antibacterial properties of the resulting molecules.

A

6-aminopenicillanic acid moiety

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8
Q

What are examples of compounds that are relatively stable to gastric acid and suitable for oral administration

A
  • penicillin V
  • amoxicillin
  • dicloxacillin
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9
Q

Penicillins can be assigned to one of three groups which are?

A
  • Penicillins (eg. penicillin G)
  • Antistaphylococcal penicillins (eg. nafcillin)
  • Extended-spectrum penicillins (aminopenicillins and antipseudomonal penicillins)
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10
Q

What group of pencillin is this?

These have the greatest activity against gram-positive organisms, gram-negative cocci, and non-β-lactamase-producing anaerobes.

A

Penicillins
(eg. penicillin G)

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11
Q

What group of pencillin is this?

These have little activity against gram-negative rods

A

Penicillins
(eg. penicillin G)

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12
Q

What group of pencillin is this?

These are susceptible to hydrolysis by β-lactamases.

A

Penicillins
(eg. penicillin G)

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13
Q

What group of pencillin is this?

These penicillins are resistant to staphylococcal β-lactamases.

A

Antistaphylococcal penicillins
(eg. nafcillin)

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14
Q

What group of pencillin is this?

They are active against staphylococci and streptococci

A

Antistaphylococcal penicillins
(eg. nafcillin)

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15
Q

What group of pencillin is this?

They are not active against enterococci, anaerobic bacteria, and gram-negative cocci and rods

A

Antistaphylococcal penicillins
(eg. nafcillin)

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16
Q

What group of pencillin is this?

These drugs retain the antibacterial spectrum of penicillin

A

Extended-spectrum penicillins
(aminopenicillins and antipseudomonal penicillins)

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17
Q

What group of pencillin is this?

These drugs have improved activity against gram-negative rods

A

Extended-spectrum penicillins
(aminopenicillins and antipseudomonal penicillins)

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18
Q

Like penicillin, they are relatively susceptible to hydrolysis by β-lactamases

A

Extended-spectrum penicillins
(aminopenicillins and antipseudomonal penicillins)

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19
Q

T or F

The activity of penicillin G was originally defined in units.

A

T

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20
Q

The minimum inhibitory concentration (MIC) of any penicillin (or other antimicrobial) is usually given in ____________

A

mcg/mL

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21
Q

Most penicillins are formulated as the ________ or ____________ of the free acid

A

sodium or potassium salt

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22
Q

Potassium penicillin G contains about 1.7 mEq of ________ per million units of penicillin (2.8 mEq/g)

A

K+

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23
Q

Nafcillin contains ________, 2.8 mEq/g.

A

Na+

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24
Q

What compounds of salt of penicillin G provide repository forms for intramuscular (IM) injection.

A
  • Procaine salts
  • Benzathine salts
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25
Q

In ____________ form, penicillin salts are stable for years at 4°C

A

dry crystalline

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26
Q

Penicillins, like all β-lactam antibiotics, inhibit bacterial growth by interfering with the ____________ of bacterial cell wall synthesis.

A

transpeptidation reaction

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27
Q

The cell wall prevents cell ________ from high osmotic pressure

A

cell lysis

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28
Q

The cell wall is composed of a complex, cross-linked polymer of polysaccharides and peptides known as ____________

A

peptidoglycan

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29
Q

The polysaccharide of the cell wall contains alternating amino sugars, namely:

A
  • N-acetylglucosamine
  • N-acetylmuramic acid
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30
Q

In the polysaccharide of the cell wall that contains an N-acetylmuramic acid sugar, a ____________ is linked to it

A

5-amino-acid peptide

31
Q

In the MOA of Penicillin, the peptidoglycan in the cell wall terminates in ___________

A

D-alanyl-D-alanine

32
Q

In the MOA of Penicillin, which enzyme is responsible for removing the terminal alanine in the process of forming a cross-link with a nearby peptide

A

Penicillin-binding protein (PBP)

33
Q

What gives the cell wall its rigidity?

A

Cross-links

34
Q

In the MOA of Penicillin, what binding inhibits the transpeptidation reaction and halts peptidoglycan synthesis, and the cell dies

A

Covalently binding of D-Ala-D-Ala substrate to the active site of PBPs

35
Q

T or F

Beta-lactam antibiotics kill bacterial cells only when they are actively growing and synthesizing cell wall

A

T

36
Q

The cell envelope of a gram-negative bacterium has an outer membrane that is ___________

A

lipid bilayer

37
Q

T or F

The lipid bilayer in a cell envelope of a bacterium is only present in a gram-negative and not in gram-positive organisms

A

T

38
Q

The lipid bilayer of a cell envelope of a gram-negative bacterium is penetrated by ________, which are proteins that form channels providing hydrophilic access to the cytoplasmic membrane

A

porins

39
Q

The cell envelope of a bacteria also has a ________ layer that is unique to bacteria and is much thicker in gram-positive organisms than in gram-negative ones.

A

peptidoglycan layer

40
Q

What are the layers that constitutes the cell wall of a bacteria?

A
  • outer membrane (lipid bilayer in gram-negative)
  • peptidoglycan
41
Q

What enzymes/membrane proteins are responsible for cross-linking peptidoglycan

A

Penicillin-binding proteins (PBPs)

42
Q

If Beta-lactamases are present where do they reside in the cell wall, where they may destroy β-lactam antibiotics that penetrate the outer membrane

A

periplasmic space or outer surface of cytoplasmic membrane

43
Q

T or F

In order to halt the peptidoglycan synthesis, the Beta-lactam works by binding the transpeptidase at the penicillin-binding protein site, resulting in inhibition of transpeptidation

A

T

44
Q

Resistance to penicillins and other β-lactams is due to one of four general mechanisms namely:

A
  1. inactivation of antibiotic by β-lactamase
  2. modification of target PBPs
  3. impaired penetration of drug to target PBPs
  4. antibiotic efflux
45
Q

What is the most common mechanism of penicillin resistance?

A

production of beta-lactamase

46
Q

Other β-lactamases, like AmpC β lactamase produced by Pseudomonas aeruginosa and Enterobacter sp and extended-spectrum β-lactamases (ESBLs) in Enterobacteriaceae,** hydrolyze both** ____________ and ___________

A

cephalosporins and penicillins

47
Q

________________ are highly resistant to hydrolysis by penicillinases and cephalosporinases

A

Carbapenems

48
Q

____________ are hydrolyzed by metallo-β-lactamases and carbapenemases, instead of hydrolysis of penicillinases and cephalosporinases

A

Carbapenems

49
Q

What are the basis of methicillin resistance in staphylococci and of penicillin resistance in pneumococci and most resistant enterococci.

A

Altered target PBPs
(These resistant organisms produce PBPs that have low affinity for binding β-lactam antibiotics)

50
Q
A
51
Q

Resistance due to impaired penetration of antibiotic occurs only in ____________ because of the impermeable outer membrane (lipid bilayer) of their cell wall, which is absent in gram-positive bacteria.

A

gram-negative species

52
Q

Beta-lactam antibiotics cross the outer membrane and enter gram-negative organisms via outer membrane protein channels called ____________

A

porins

53
Q

Gram-negative organisms also may produce an ____________, which consists of cytoplasmic and periplasmic protein components that efficiently transport some β-lactam antibiotics

A

efflux pump

54
Q

Gastrointestinal absorption of ____________ is erratic, so it is not suitable for oral administration

A

nafcillin

55
Q

What penicillin drugs are acid-stable and relatively well absorbed, producing serum concentrations in the range of 4–8 mcg/mL after a 500-mg oral dose

A
  • Dicloxacillin
  • Ampicillin
  • Amoxicillin
56
Q

Absorption of most oral penicillins (amoxicillin being an exception) is impaired by food, and the drugs should be administered at least ____________ before or after a meal

A

1–2 hours

57
Q

________________ of penicillin G is preferred to the intramuscular route because of irritation and local pain from intramuscular (IM) injection of large doses.

A

Intravenous administration (IV)

58
Q

Highly protein-bound penicillins like ____________ generally achieve lower free-drug concentrations in serum than less protein-bound penicillins

A

nafcillin

59
Q

Penicillins are ________, thus it works well in intracellular concentrations than those found in extracellular fluids.

A

polar

60
Q

____________ and ____________ penicillins are formulated to delay absorption, resulting in prolonged blood and tissue concentrations

A

Benzathine and procaine

61
Q

T or F

Penicillin is also excreted into sputum and breast milk to levels 3–15% of those in the serum

A

T

62
Q

Penicillin is rapidly excreted by the _______

A

kidneys (majority)

63
Q

The normal half-life of penicillin G is approximately ____________ but, in renal failure, may be as long as 10 hours

A

30 minutes

64
Q

T or F

Ampicillin and the extended-spectrum penicillins are secreted more slowly than penicillin G and have half-lives of 1 hour

A

T

65
Q

Give the ROA

Penicillins: Penicillin G

A

Intravenous (IV)

66
Q

Give the ROA

Penicillins: Penicillin V

A

Oral Administration (PO)

67
Q

Give the ROA

Antistaphylococcal penicillins: Cloxacillin, dicloxacillin

A

Oral Administration (PO)

68
Q

Give the ROA

Antistaphylococcal penicillins:
Nafcillin

A

Intravenous (IV)

69
Q

Give the ROA

Antistaphylococcal penicillins:
Oxacillin

A

Intravenous (IV)

70
Q

Give the ROA

Extended-spectrum penicillins:
Amoxicillin

A

Oral Administration (PO)

71
Q

Give the ROA

Extended-spectrum penicillins:
Amoxicillin/potassium
clavulanate

A

Oral Administration (PO)

72
Q

Give the ROA

Extended-spectrum penicillins:
 Piperacillin/tazobactam

A

Intravenous (IV)

73
Q

Nafcillin is primarily cleared by ____________ excretion

A

biliary excretion

74
Q
A

MT6314 (PCOL) (6 decks)

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