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Pharmacology > Cell wall synthesis inhibitors > Flashcards

Cell wall synthesis inhibitors Flashcards

1
Q

What is the major group of cell wall synthesis inhibitors?

A

Beta Lactams

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2
Q

What molecular feature distinguishes beta lactams?

A

Beta lactam ring (site of action and resistance)

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3
Q

What was the first beta lactam discovered?

A

Penicillin

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4
Q

What is the mechanism of action of beta lactam drugs?

A
  • Inhibits peptidoglycan
    synthesis
  • b-lactam agents bind to the
    transpeptidase and inhibit cell
    wall synthesis
  • Disrupts bacterial cell wall
    integrity and causes lysis
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5
Q

What is the name of the molecule that Beta Lactams bind to?

A

Penicillin binding protein (PBP), the transpeptidase

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6
Q

What is a mechanism of resistance to penicillin that bacteria can acquire from other bacteria?

A

Bacteria acquire new PBP from other bacteria that are
resistant to b-lactams

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7
Q

What are some drug penetration mechanisms of resistance?

A

Inability to penetrate to site of action
* Gram (–) outer membrane tough to penetrate
* Gram (-) outer membrane modified with impenetrable porins–no longer permeable
* Can’t handle pus, acidic pH

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8
Q

What is the biggest mechanism of resistance to beta-lactam drugs?

A

b-lactamase enzymes present in bacteria that
target the active site of the drug

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9
Q

What group of penicillin derivatives can traverse the outer membrane of gram negatives? What are 2 drawbacks of use of these drugs?

A
  • Aminopenicillins (ampicillin and amoxicillin) have added amino groups to get through the porins of the outer membrane in gram negative bacteria
  • These drugs are vulnerable to beta-lactamases so are combined with beta-lactamase inhibitors like clavulenic acid (+ amoxicillin = clavamox)
  • Oral administration will kill hindgut fermenters
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10
Q

What drug group is less vulnerable to beta lactamase?

A

Methicillin (antistaphylococcal penicilin) is chemically modified to be less vulnerable to beta-lactamases

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11
Q

How does clavulenic acid work?

A

it is a b-lactamase inhibitor, it binds the
b-lactamase enzyme

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12
Q

What is the spectrum of activity of Penicillin?

A
  • Most Gram (+) aerobes
  • Most Gram (+) anaerobes
  • Little activity against Staph aureus sp.
  • Gram (-) are typically resistant
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13
Q

What are the most important side effects of Penicillin?

A

Penicillin hypersensitivity: true for all penicillin
classes!!!
* In order of decreasing frequency: urticaria, fever,
bronchospasm, vasculitis, serum sickness, exfoliative
dermatitis, anaphylaxis
* Can occur without any prior exposure
* Reactions after IM injection of Procaine

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14
Q

What are the 4 types of penicillin derivatives and examples?

(5 total)

A
  • Anti-staph penicillins: Methicillin
  • Aminopenicillins: Amoxicillin, ampicillin
  • Anti-pseudomonas penicillin
  • Potentiated penicillin: Clavamox = Amoxicillin + Clavulenic acid
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15
Q

What is therapy goal with use of Antistaphylococcal penicillins and what is an example drug?

A

Methicillin
Goal is treatment of penicillin-resistant bacteria because they are not as vulnerable to b-lactamases

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16
Q

What is therapeutic goal of treatment with Aminopenicillins and what are 2 example drugs?

A

Amoxicillin and Ampicillin
Goal is to treat gram negatives because spectrum of Activity:
* Extended spectrum to include some Gram (-)
-E. coli
-Proteus mirabilis
-Salmonella
* Improved ability to penetrate the outer membrane
of Gram (-) bacteria
* Susceptible to b-lactamases

17
Q

What is the most important adverse effect of Aminopenicillins?

A

Oral administration will KILL HINDGUT FERMENTERS (horses, guinea pigs, rabbits, hamsters, gerbils)

18
Q

What is therapeutic goal of treatment with Antipseudomonal penicillins?

A

Spectrum of Activity extended to include Gram (-)
* Pseudomonas aeruginosa
* Enterobacter
* Proteus

19
Q

How are antipseudomonal penicillins given?

A

Not good orally, typically given parenterally

20
Q

What is therapeutic goal of potentiated penicillins and an example drug?

A

Potentiated penicillin: Clavamox = Amoxicillin + Clavulenic acid
Penicillins mixed with b-lactamase inhibitors
Spectrum of activity
* Staphylococci sp.
* Bacterioides
* E. coli

21
Q

What is the mechanism of action of cephalosporins?

A

Inhibits peptidoglycan
synthesis, same as penicillins

22
Q

What type of penicillin would you use to treat enterobacter, proteus, and pseudomonas? How would you give them?

A

Antipseudomonal Penicillins
Not good orally, typically given parenterally

23
Q

What is the difference between first, second, third, and fourth generation cephalosporins?

A

First generation: mostly Gram (+), modest Gram (-)
Second generation: added Gram (-)
Third generation: less Gram (+), more Gram (-)
Fourth generation: extended spectrum from 3rd
generation

24
Q

What type of drug and generation is Ceftiofur?

A

3rd generation cephalosporin

25
Q

What are most important side effects of cephalosporins in general? Of Ceftiofur?

A

In general, very safe drugs, hypersensitivity, most common, similar to penicillins
Antimicrobial induced colitis from Ceftiofur
* Younger horses, high stress (racehorses), given IV fast instead of IM

26
Q

Which cephalosporin can you use IM?

A

Ceftiofur

27
Q

Which generation of cephalosporins is most resistant to beta-lactamases?

A

Fourth generation

28
Q

What generation of cepahlosporin would you use to treat an infection with a gram positive organism?

A

First generation

29
Q

Do cephalosporins need to be metabolized to be active?

A

Little metabolism…
EXCEPTION! 3rd generation Ceftiofur requires
metabolization to active metabolite for antimicrobial
activity (desfuroylceftiofur)

30
Q

What is mechanism of action of carbapenems?

A

Disrupts bacterial cell wall synthesis by binding penicillin binding proteins; resistant to most b lactamases

31
Q

What are the three subclasses of beta-lactam drugs?

A

Penicillins and derivatives
Cephalosporins
Carbapenems

32
Q

What is the therapeutic use of carbapenems?

A

Most powerful bactericidal activity of the b-lactams
Big gun, use as last resort

33
Q

What are the most important side effects of carbapenems?

A

Extensive metabolism by renal tubules to potentially toxic compound

34
Q

What are the non-beta lactam cell wall synthesis inhibitor drugs?

A

Bacitracin
Vancomycin
Teixobactin

35
Q

When would you use bacitracin? Why?

A

Only used topically: ophthalmic and dermatologic ointments
VERY NEPHROTOXIC if given parenterally

36
Q

What is the most important thing to know about vancomycin?

A

NO VETERINARY FORMULATIONS
APPROVED—BIG GUN!

37
Q

What is the method of action of Teixobactin? Spectrum of activity?

A

Works on 3 different sites to disrupt cell wall synthesis
– Binds Lipid II—precursor for peptidoglycan component of cell wall (same site of action for Vancomycin)
– Binds Lipid III—precursor for wall teichoic acid (WTA), building block of cell wall
– Blocks precursor recycling—leads to depletion of cell wall components
Spectrum of activity
– Gram(+)—attacks sugar molecules in cell wall
– Gram(-)—resistant due to outer membrane

38
Q

Which generation of cephalosporins is most resistant to beta-lactamases?

A

Fourth generation

Pharmacology (9 decks)

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