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(UNI) Chemotherapy & Selective Toxicity (3rd Year) > Anti-Bacterials - Cell Wall > Flashcards

Anti-Bacterials - Cell Wall Flashcards

1
Q

Name the Beta-Lactam antibiotics.

A

Penecillins, Cephalosporins, Carbapenems, Monobactams.

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2
Q

Name the Glycopeptides.

A

Vancomycin, Teicoplanin.

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3
Q

How does a Gram negative cell wall vary from that of a Gram positive cell wall?

A

The Gram negative cell wall has an inner membrane, an outer membrane, and a layer of peptidoglycan inbetween the two. The Gram positive cell wall only has one membrane and a larger layer of peptidoglycan.

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4
Q

How do beta-lactams and glycopeptides work to kill bacterial cells?

A

Both beta-lactams and glycopeptides inhibit the production of peptidoglycan which is essential to nearly all bacteria.

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5
Q

What is the function of peptidoglycan in the bacterial cell wall?

A

Peptidoglycan provisdes the bacterial cell wall with strength through the cross linking of initiated by transpeptidase.

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6
Q

Is there a selective toxicity issue with targeting the peptidoglycan in bacterial cell walls?

A

No as there is no similar molecule in the human cell.

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7
Q

How does transpsptidase work in the formation of cross links in peptidoglycan?

A

Transpeptidase removes the D-alanine and cross links the peptides with pentaglycine.

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8
Q

Describe the beta-lactamase ring.

A

A 4 membered ring containing a carbonyl group in the bottom left and a NH group in the borrom right.

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9
Q

How do penecillins differ from other beta-lactam antibiotics?

A

Their beta-lactam ring is bound to a 5-membered ring containing a sulfur atom in the top potition.

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10
Q

What effects do the side chains of penecillins have on the drug? How is this chaice achieved in non-synthetic penecillins?

A

They change the drugs physiochemical and pharmacological properties. This change is achieved (in non-synthetic penicillins) by changing the substrate with which the penicillin producing mould (penicillium) is fermented with.

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11
Q

What is penecillium fermented with to benzyl penicillin (penicillin G)?

A

Phenylacetic acid.

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12
Q

Can benzyl penicillin (penicillin G) be given orally?

A

No as it has no protection against the acidic stomach environment, leading to acid hydrolysis.

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13
Q

What is penicillium fermented with to produce Phenoxymethylpenecillin (Penicillin V)?

A

Phenoxyacetic acid.

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14
Q

How do penecillins act to block the action of transpeptidase?

A

Transpeptidase nucleophillically attacks the carbonyl group on the beta-lactam ring of the drug. A covalent bond is formed. This permenantly inhibits the action of transpeptidase as the drug cant be released. This is because there is no NH2 group to break the covalent bond through nucleophilic attack.

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15
Q

Are penicillins V and G activa against Gram negative bacteria?

A

No.

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16
Q

How are semisynthetic penicillins produced?

A

The penicillium is starved of any substrate it produces the penicillin nucleus. This is converted to active penicillins by reaction with an activated acid.

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17
Q

Can beta-lactam rings be produced synthetically?

A

Yes but they require harsh chamical reactions, lots of energy, and have a low yield. There needs to be lots of energy to get the carbon into position as it isnt in its normal conformation.

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18
Q

What enzyme is responsible for penicillin resistance?

A

Beta-lactamase.

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19
Q

How does beta-lactamase work?

A

By breaking apart the beta-lactam ring at the carbonyl carbon. This removes the reactive properties of the ring and removes its antibacterial action.

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20
Q

How can the activity of beta-lactamase be reduced?

A

Through the use of beta-lactamase inhibitors.

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21
Q

Name some beta-lactamase inhibitors.

A

Clavulanic acid, sulbactam, tezobactam.

22
Q

Who developed clavulanic acid and what is it commonly used with?

A

Beecham (GSK). It is commonly used with amoxicillin as co-amoxiclav.

23
Q

Who developed sulbactam and what is it commonly used with?

A

Pfizer. It is commonly used with ampicillin.

24
Q

Tazobactam.

A

Wyeth. It is commonly given with piperacillin.

25
Q

Do beta-lactamase inhibitors have any intrinsic anti-bacterial activity?

A

Yes but only very weak activity, they cant be given alone for therapeutic effect.

26
Q

What percentage of patients show a mild adverse drug reaction to penicillins?

A

1%.

27
Q

What type of hypersensitivity is a penicillin reaction?

A

A type 1 hypersenitivity (IgE), the body noticing the penicillin as non-self.

28
Q

Describe the process of haptenization.

A

The reaction of the beta lactam ring with proteins in the blood, usually albumin. This is a slow and rare reaction.

29
Q

Describe the cephalosporin nucleus.

A

A beta-lactam ring bound to a six-membered ring containing a sulfur atom at the top, a carboxylic acid at the bottom, and a double bond in the SE position.

30
Q

How can one change the properties of a cephalosporin?

A

By altering the side chains on the left and right of the nucleus.

31
Q

Describe the carbapenem nucleus.

A

The same as the penicillin nucleus (beta lactam bound to a 5-membered ring with a nitrogen atom in the top position) but with a double bond in the 5-membered ring.

32
Q

How can one change the properties of a carbapenem?

A

By altering the side chains on the left and right of the nucleus.

33
Q

What was the first and most potent carbapenem?

A

Thienamycin.

34
Q

Give some common carbapenems.

A

Imipenem, Meropenem.

35
Q

Is imipenem resistant to renal peptidase?

A

No.

36
Q

Is meropenem resistant to renal peptidase?

A

Yes.

37
Q

Describe the monobactam nucleus.

A

This nucleus is made up of the beta-lactam ring only.

38
Q

Are monobactams tollerated by patients with a penicillin allergy?

A

Yes, possibly due to a difference in the core of the molecule.

39
Q

What is the only used monobactam?

A

Aztreonam.

40
Q

Describe the structure of glycopeptides?

A

Glycopeptides are formed of a peptide chain core and a sugar attachment.

41
Q

In what two ways do glycopeptides block the formation of peptidoglycan in the bacterial cell wall?

A

By preventing the formation of the linear glycan (NAG-NAM) strands by transglycosylase. Inhibiting peptide cross linking by transpeptidase.

42
Q

Describe the 3D structure of glycopeptides.

A

It has a cage like structure so it captures the D-Ala-D-Ala and interacts with it via hydrogen and ionic bonds.

43
Q

Can one molecule of a glycopeptide carry out multiple reactions? Why?

A

Yes because it doesnt bind covalently.

44
Q

Why do glycopepties have a narrow therapeutoc window?

A

Baceuse the binding occurs at low concentrations.

45
Q

Are glycopeotides used in community? Why?

A

No because they have a narrow therapeutic wondow and require the monitoring available in a hospital.

46
Q

Describe the activity of vancomycin against Gram negative and Gram positive bacteria.

A

Active against Gram positive bacteria, not activa against Gram negative bacteria as it cant get through the cell wall.

47
Q

Why is full synthetic production of vancomycin hard?

A

Because the structure is very complicates, consisting of a lot of chirality.

48
Q

What is odd about teicoplanin?

A

Formulations are comprised of at least 5 compounds with the same glycopeptide core. This made it hard to gain a license.

49
Q

What type of bacterial cells have no pentaglycine bridges in their cell wall?

A

Gram-negative cells.

50
Q

What is unusual, chemically, about a beta-lactam ring?

A

The carbons in it are at a 90-degree bond angle which is not their normal conformation.

(UNI) Chemotherapy & Selective Toxicity (3rd Year) (18 decks)

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