Modification of Cephalosporins
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Questions and Answers

What is the result of modifying the R2 side chain of the third-generation cephalosporins?

  • Loss of anaerobic activity
  • Loss of antistaphylococcal activity
  • Gain of antipseudomonal activity (correct)
  • Increase in gram-positive activity

    • What is a characteristic of cefepime in regards to gram-negative β-lactamases?

  • It only affects chromosomally encoded inducible AmpC β-lactamases
  • It has no effect on gram-negative β-lactamases
  • It is resistant to hydrolysis (correct)
  • It is highly susceptible to hydrolysis

    • What is a limitation of cefepime?

  • It is highly susceptible to hydrolysis by gram-negative β-lactamases
  • It is only effective against P. aeruginosa
  • It has no activity against aerobic gram-positive cocci
  • It has very limited anaerobic activity (correct)

    • What is a unique property of cefepime compared to third-generation cephalosporins?

    <p>It has enhanced activity against P. aeruginosa</p> Signup and view all the answers

    What is the group at R1 that remains unchanged in the development of fourth-generation cephalosporins?

    <p>Aminothiazolyl group</p> Signup and view all the answers

    What is a characteristic of cefepime's interaction with PBPs?

    <p>It has high affinity for PBPs of many gram-negative bacteria</p> Signup and view all the answers

    What is the mechanism of action of cephalosporins?

    <p>By inhibiting the activity of bacterial enzymes that assemble peptidoglycan</p> Signup and view all the answers

    Which generation of cephalosporins has strong activity against aerobic gram-positive bacteria?

    <p>Fifth-generation</p> Signup and view all the answers

    What is a characteristic of first-generation cephalosporins?

    <p>Good activity against aerobic gram-positive bacteria</p> Signup and view all the answers

    What is a characteristic of second-generation cephalosporins?

    <p>Enhanced activity against aerobic gram-negative bacteria</p> Signup and view all the answers

    Which generation of cephalosporins is most useful in the treatment of infections caused by aerobic gram-negative bacteria?

    <p>Third-generation</p> Signup and view all the answers

    Which class of antibiotics do cephalosporins belong to?

    <p>Beta-lactams</p> Signup and view all the answers

    What is a characteristic of third-generation cephalosporins?

    <p>Strong activity against aerobic gram-negative bacteria</p> Signup and view all the answers

    How are cephalosporins grouped?

    <p>By their generation</p> Signup and view all the answers

    What is the type of group present at R1 in the structure of cefepime?

    <p>Aminothiazolyl group</p> Signup and view all the answers

    What is the type of group present at R2 in the structure of cefepime?

    <p>Pyrrolidine group</p> Signup and view all the answers

    Which of the following bacteria is susceptible to fourth-generation cephalosporins?

    <p>Escherichia coli</p> Signup and view all the answers

    What is the activity of fourth-generation cephalosporins against Streptococcus pneumoniae?

    <p>Modest activity</p> Signup and view all the answers

    Which of the following is not a Gram-positive bacteria susceptible to fourth-generation cephalosporins?

    <p>Klebsiella pneumoniae</p> Signup and view all the answers

    What is the activity of fourth-generation cephalosporins against Proteus spp.?

    <p>Strong activity</p> Signup and view all the answers

    Which of the following is a Gram-negative bacteria susceptible to fourth-generation cephalosporins?

    <p>Escherichia coli</p> Signup and view all the answers

    What is the activity of fourth-generation cephalosporins against Staphylococcus aureus?

    <p>Modest activity</p> Signup and view all the answers

    What is the functional group attached to the nitrogen atom in the structure of glycopeptides?

    <p>Amino group</p> Signup and view all the answers

    What is the central atom in the PO3H2 group of the glycopeptide structure?

    <p>Phosphorus</p> Signup and view all the answers

    Which of the following is a characteristic of the structure of telavancin?

    <p>It has a lipophilic side chain</p> Signup and view all the answers

    What is the functional group attached to the oxygen atom in the structure of glycopeptides?

    <p>Hydroxyl group</p> Signup and view all the answers

    Which of the following glycopeptides has a decylaminoethyl side chain?

    <p>Telavancin</p> Signup and view all the answers

    What is the nitrogen-containing group in the structure of glycopeptides?

    <p>Amino group</p> Signup and view all the answers

    What is the enzyme that hydrolyzes imipenem in the kidney?

    <p>Dehydropeptidase I</p> Signup and view all the answers

    What is the primary activity of carbapenems?

    <p>Aerobic, anaerobic, and fungal activity</p> Signup and view all the answers

    How does ertapenem compare to other carbapenems in terms of activity against aerobic gram-positive bacteria?

    <p>Less active</p> Signup and view all the answers

    What is the primary activity of aztreonam?

    <p>Aerobic gram-negative bacteria</p> Signup and view all the answers

    What is the route of administration for aztreonam?

    <p>Parenteral</p> Signup and view all the answers

    What is a characteristic of monobactams?

    <p>Narrow spectrum of activity</p> Signup and view all the answers

    What is the primary mechanism of resistance to carbapenems in Pseudomonas aeruginosa?

    <p>Alterations in porin</p> Signup and view all the answers

    What is the purpose of co-administering cilastatin with imipenem?

    <p>To prevent degradation of imipenem by dehydropeptidase I</p> Signup and view all the answers

    Study Notes

    Cephalosporins

    • Cephalosporins vary in their activities, with generations having distinct characteristics.
    • Fourth-generation cephalosporins, such as cefepime, have enhanced activity against aerobic gram-negative bacteria, including Pseudomonas aeruginosa, and are relatively resistant to hydrolysis by gram-negative β-lactamases.

    Structure of Cefepime

    • Cefepime has a polar pyrrolidine group at R2, which allows for rapid penetration through the outer membrane of many gram-negative bacteria.
    • The aminothiazolyl group at R1 is typical of many third-generation cephalosporins.

    Antimicrobial Activity of Cefepime

    • Cefepime has excellent activity against:
      • Streptococcus pyogenes
      • Viridans streptococci
      • Many Streptococcus pneumoniae
      • Escherichia coli
      • Klebsiella pneumoniae
      • Proteus spp.
    • Modest activity against Staphylococcus aureus
    • Limited anaerobic activity

    Generalizations of Cephalosporin Generations

    • First-generation cephalosporins have good activity against aerobic gram-positive bacteria.
    • Second-generation cephalosporins have modest activity against aerobic gram-positive, aerobic gram-negative, and anaerobic bacteria.
    • Third-generation cephalosporins have strong activity against aerobic gram-negative bacteria.
    • Fourth-generation cephalosporins have especially enhanced activity against aerobic gram-negative bacteria.
    • Fifth-generation cephalosporins have strong activity against aerobic gram-negative bacteria and excellent activity against aerobic gram-positive bacteria.

    Carbapenems

    • Carbapenems have excellent activity against aerobic gram-positive, aerobic gram-negative, and anaerobic bacteria.
    • Imipenem is hydrolyzed by dehydropeptidase I in the kidney and must be given with cilastatin.

    Monobactams

    • Aztreonam, the only commercially available monobactam, is effective against aerobic gram-negative bacteria and is available for parenteral use only.

    Glycopeptides

    • The structure of glycopeptides, such as vancomycin and telavancin, is distinct from β-lactams.
    • Telavancin has a lipophilic decylaminoethyl side chain, which is not present in vancomycin.

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    Description

    This quiz is about the modifications of cephalosporins, specifically the creation of fourth-generation cephalosporin cefepime. It discusses the changes made to the R2 side chain to improve antistaphylococcal activity.

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