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?

It has enhanced activity against P. aeruginosa Signup and view all the answers

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

Aminothiazolyl group Signup and view all the answers

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

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

What is the mechanism of action of cephalosporins?

By inhibiting the activity of bacterial enzymes that assemble peptidoglycan Signup and view all the answers

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

Fifth-generation Signup and view all the answers

What is a characteristic of first-generation cephalosporins?

Good activity against aerobic gram-positive bacteria Signup and view all the answers

What is a characteristic of second-generation cephalosporins?

Enhanced activity against aerobic gram-negative bacteria Signup and view all the answers

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

Third-generation Signup and view all the answers

Which class of antibiotics do cephalosporins belong to?

Beta-lactams Signup and view all the answers

What is a characteristic of third-generation cephalosporins?

Strong activity against aerobic gram-negative bacteria Signup and view all the answers

How are cephalosporins grouped?

By their generation Signup and view all the answers

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

Aminothiazolyl group Signup and view all the answers

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

Pyrrolidine group Signup and view all the answers

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

Escherichia coli Signup and view all the answers

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

Modest activity Signup and view all the answers

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

Klebsiella pneumoniae Signup and view all the answers

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

Strong activity Signup and view all the answers

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

Escherichia coli Signup and view all the answers

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

Modest activity Signup and view all the answers

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

Amino group Signup and view all the answers

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

Phosphorus Signup and view all the answers

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

It has a lipophilic side chain Signup and view all the answers

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

Hydroxyl group Signup and view all the answers

Which of the following glycopeptides has a decylaminoethyl side chain?

Telavancin Signup and view all the answers

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

Amino group Signup and view all the answers

What is the enzyme that hydrolyzes imipenem in the kidney?

Dehydropeptidase I Signup and view all the answers

What is the primary activity of carbapenems?

Aerobic, anaerobic, and fungal activity Signup and view all the answers

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

Less active Signup and view all the answers

What is the primary activity of aztreonam?

Aerobic gram-negative bacteria Signup and view all the answers

What is the route of administration for aztreonam?

Parenteral Signup and view all the answers

What is a characteristic of monobactams?

Narrow spectrum of activity Signup and view all the answers

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

Alterations in porin Signup and view all the answers

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

To prevent degradation of imipenem by dehydropeptidase I 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.