Cephalosporin Antibiotics
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Questions and Answers

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

  • E. coli (correct)
  • Enterococci
  • MRSA
  • L. monocytogenes

    • What is the main difference between true cephalosporins and cephamycins?

  • Their spectrum of activity against gram-negative bacteria
  • The fungus they were originally isolated from (correct)
  • Their activity against anaerobes, intracellular bacteria, and spirochetes
  • Their ability to bind to PBPs of MRSA and MRSE

    • Why are first-generation cephalosporins ineffective against MRSA and MRSE?

  • Because they are incapable of binding to their PBPs (correct)
  • Because they are not effective against gram-negative bacteria
  • Because they are not effective against anaerobes, intracellular bacteria, and spirochetes
  • Because they are not effective against Streptococcus pneumoniae

    • What is the main limitation of first-generation cephalosporins against gram-negative bacteria?

    <p>Their inability to protect against -lactamases of gram-negative bacteria</p> Signup and view all the answers

    Which of the following bacteria is not susceptible to first-generation cephalosporins?

    <p>L. monocytogenes</p> Signup and view all the answers

    What is the main advantage of second-generation cephalosporins over first-generation cephalosporins?

    <p>Their increased ability to protect against -lactamases of gram-negative bacteria</p> Signup and view all the answers

    What is the activity of true cephalosporins against Gram-positive bacteria?

    <p>Equivalent to first-generation agents</p> Signup and view all the answers

    Which of the following is not a Gram-negative bacterium that is susceptible to second-generation cephalosporins?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What is the anaerobic activity of cefoxitin and cefotetan?

    <p>Moderate anaerobic activity</p> Signup and view all the answers

    Which generation of cephalosporins has activity against anaerobic bacteria?

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

    What is the activity of cefoxitin and cefotetan against Gram-positive bacteria?

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

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

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

    What is the activity of true cephalosporins against Gram-negative bacteria?

    <p>Equivalent to first-generation agents</p> Signup and view all the answers

    Which of the following is a characteristic of second-generation cephalosporins?

    <p>Moderate anaerobic activity</p> Signup and view all the answers

    What is the difference in activity against aerobic gram-positive bacteria between individual second-generation cephalosporins?

    <p>The cephamycins have relatively limited activity</p> Signup and view all the answers

    What is the strength of the second-generation cephalosporin agents?

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

    Which bacteria are the true cephalosporins also active against?

    <p>Neisseria spp. and H. influenzae</p> Signup and view all the answers

    What is the consequence of the additional methoxy group on the β-lactam ring of the cephamycins?

    <p>Enhanced stability to the β-lactamases of some anaerobes</p> Signup and view all the answers

    What is the trade-off for the cephamycins' enhanced anaerobic activity?

    <p>Decreased activity against staphylococci and streptococci</p> Signup and view all the answers

    Why are agents like cefotetan and cefoxitin categorized as cephalosporins?

    <p>They are chemically and pharmacologically similar to cephalosporins</p> Signup and view all the answers

    What is the primary limitation of first-generation cephalosporins against Staphylococcus aureus?

    <p>Lack of activity against MRSA and MRSE</p> Signup and view all the answers

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

    <p>E.coli</p> Signup and view all the answers

    What is the difference between true cephalosporins and cephamycins?

    <p>Cephamycins are derivatives of Streptomyces lactamdurans</p> Signup and view all the answers

    What is the main advantage of second-generation cephalosporins over first-generation cephalosporins?

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

    What is the primary activity of cefoxitin and cefotetan?

    <p>High activity against anaerobes</p> Signup and view all the answers

    What is the primary advantage of cephamycins over true cephalosporins?

    <p>Enhanced activity against anaerobes</p> Signup and view all the answers

    What is a common characteristic of second-generation cephalosporins?

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

    Which of the following bacteria is not affected by the additional methoxy group on the β-lactam ring of the cephamycins?

    <p>B. fragilis</p> Signup and view all the answers

    What is the main difference in activity between true cephalosporins and cephamycins against aerobic gram-positive bacteria?

    <p>Cephamycins have relatively limited activity</p> Signup and view all the answers

    Which of the following is a characteristic of the cephamycins?

    <p>Enhanced stability to the β-lactamases of some anaerobes</p> Signup and view all the answers

    Why are agents like cefotetan and cefoxitin categorized as cephalosporins?

    <p>They have similar pharmacological activity to cephalosporins</p> Signup and view all the answers

    What is the consequence of the additional methoxy group on the β-lactam ring of the cephamycins?

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

    What is the key difference in the nucleus of cephalosporins compared to penicillin?

    <p>The -lactam ring is fused to a six-member dihydrothiazine ring</p> Signup and view all the answers

    What is one advantage of the cephalosporin core over the penicillin core?

    <p>It is more resistant to cleavage by -lactamases</p> Signup and view all the answers

    What is the site of attachment for cephalosporins that exerts their antibiotic effect?

    <p>PBP receptors</p> Signup and view all the answers

    What are the two sites on the cephalosporin core that can be modified?

    <p>R1 and R2</p> Signup and view all the answers

    What is the ring structure fused to the -lactam ring in cephalosporins?

    <p>Six-member dihydrothiazine ring</p> Signup and view all the answers

    What is the mechanism of action of cephalosporins?

    <p>Inhibiting peptidoglycan synthesis</p> Signup and view all the answers

    What is a key advantage of cephalosporins over penicillin?

    <p>They have two sites, R1 and R2, that can be modified</p> Signup and view all the answers

    What is the structural feature of cephalosporins that allows them to be more resistant to -lactamases?

    <p>The -lactam ring is fused to a six-member dihydrothiazine ring</p> Signup and view all the answers

    Study Notes

    First-Generation Cephalosporins

    • Effective against infections caused by many strains of Staphylococcus aureus
    • Ineffective against MRSA, MRSE, and highly penicillin-resistant Streptococcus pneumoniae
    • Limited activity against aerobic and facultative gram-negative bacteria
    • Susceptible to some strains of E. coli, Klebsiella pneumoniae, and Proteus mirabilis
    • Moderate to poor activity against anaerobes, intracellular bacteria, and spirochetes

    Second-Generation Cephalosporins

    • Divided into two groups: true cephalosporins (e.g. cefuroxime) and cephamycins (e.g. cefotetan and cefoxitin)
    • Cephamycins are derivatives of a parent compound from Streptomyces lactamdurans
    • True cephalosporins have activity equivalent to first-generation agents against gram-positive bacteria
    • Cephamycins have little activity against gram-positive bacteria
    • Active against gram-negative bacteria, including Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Haemophilus influenzae, and Neisseria spp.
    • Cefoxitin and cefotetan have moderate anaerobic activity

    Cephamycins

    • Include cefotetan and cefoxitin
    • Have relatively limited activity against aerobic gram-positive bacteria
    • Have enhanced stability to the β-lactamases of some anaerobes, such as B. fragilis
    • Diminished activity against staphylococci and streptococci due to decreased affinity for the PBPs of these bacteria

    Second-Generation Cephalosporins

    • Not actually cephalosporins, but chemically and pharmacologically similar
    • Differ in activity against aerobic gram-positive bacteria
    • True cephalosporins are as active against aerobic gram-positive cocci as first-generation agents
    • Cephamycins (cefotetan and cefoxitin) have relatively limited activity against these bacteria

    Activity Against Bacteria

    • Second-generation agents have increased activity against:
      • Aerobic and facultative gram-negative bacteria
      • E. coli, K. pneumoniae, and P. mirabilis
      • Neisseria spp.
      • H. influenzae (including β-lactamase-producing strains)
    • Cephamycins have enhanced stability against β-lactamases of some anaerobes (e.g., B. fragilis)
    • True cephalosporins are more active against H. influenzae and Neisseria spp.

    Comparison with First-Generation Cephalosporins

    • First-generation cephalosporins have limited activity against:
      • Aerobic and facultative gram-negative bacteria
      • Anaerobes, intracellular bacteria, and spirochetes
    • First-generation cephalosporins are ineffective against:
      • MRSA and MRSE
      • Many highly penicillin-resistant S. pneumoniae
      • L. monocytogenes and enterococci

    Structure and Mechanism of Action

    • Cephalosporin nucleus is 7-aminocephalosporanic acid
    • β-Lactam ring is fused to a six-member dihydrothiazine ring
    • Cephalosporin core has two major advantages over penicillin core:
      1. Intrinsic resistance to cleavage by β-lactamases
      2. Two sites (R1 and R2) for modification
    • Cephalosporins exert their effects by attaching to and inhibiting PBPs, preventing peptidoglycan synthesis

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    Description

    Learn about the effectiveness of cephalosporin antibiotics against various bacterial strains, including Staphylococcus aureus, MRSA, and Streptococcus pneumoniae.

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