Antibiotics: Penicillins and Bacterial Enzymes
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Questions and Answers

Which of the following bacteria produces penicillinases that degrade natural penicillins?

  • Actinomyces israelii
  • Treponema pallidum
  • Bacteroides fragilis (correct)
  • Leptospira spp.

    • What is a limitation of natural penicillins?

  • They are ineffective against bacteria that produce penicillinases
  • They are ineffective against bacteria with altered PBPs (correct)
  • They are ineffective against gram-positive bacteria
  • They are ineffective against some anaerobic bacteria

    • Which of the following bacteria is susceptible to natural penicillins?

  • Streptococcus pneumoniae
  • Neisseria meningitidis
  • Haemophilus influenzae
  • All of the above (correct)

    • What is the mechanism of resistance of methicillin-resistant S.aureus (MRSA) to antistaphylococcal penicillins?

    <p>Altered PBPs</p> Signup and view all the answers

    What is the characteristic of antistaphylococcal penicillins?

    <p>They have bulky R side chains</p> Signup and view all the answers

    Which of the following is NOT a limitation of natural penicillins?

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

    Which of the following bacteria is resistant to antistaphylococcal penicillins?

    <p>Methicillin-resistant S.aureus (MRSA)</p> Signup and view all the answers

    What is the mechanism of action of antistaphylococcal penicillins?

    <p>Inhibition of cell wall synthesis</p> Signup and view all the answers

    What is an important feature of extended-spectrum penicillins?

    <p>They are active against even more enteric gram-negative rods and P. aeruginosa</p> Signup and view all the answers

    What is the effect of adding a β-lactamase inhibitor to an aminopenicillin?

    <p>It expands the spectrum of these agents to include many aerobic gram-negative bacilli and anaerobes</p> Signup and view all the answers

    What is a characteristic of antistaphylococcal penicillins?

    <p>They are useful in treating infections caused by Staphylococcus</p> Signup and view all the answers

    What is a difference between natural penicillins and aminopenicillins?

    <p>Aminopenicillins have improved activity against aerobic gram-negative bacilli</p> Signup and view all the answers

    What is a characteristic of extended-spectrum penicillins?

    <p>They have improved activity against aerobic gram-negative bacilli, including P. aeruginosa</p> Signup and view all the answers

    What is the result of using extended-spectrum penicillins in combination with β-lactamase inhibitors?

    <p>They are among the most powerful antibacterial agents available today</p> Signup and view all the answers

    What is a feature of natural penicillins?

    <p>They have moderate activity against aerobic gram-positive bacteria and anaerobic bacteria</p> Signup and view all the answers

    What is the mechanism of action of penicillins?

    <p>They bind to enzymes that function to assemble bacterial cell walls</p> Signup and view all the answers

    What is the source of the first members of the cephalosporin class of antibiotics?

    <p>Fungus Cephalosporium acremonium</p> Signup and view all the answers

    What is the categorization scheme used to organize cephalosporins?

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

    What do cephalosporins have in common with penicillins?

    <p>Both are beta-lactam antibiotics</p> Signup and view all the answers

    What is the common feature of the structure of cephalosporins?

    <p>Two side chains</p> Signup and view all the answers

    What is the name of the fungus that was the source of the first members of the cephalosporin class of antibiotics?

    <p>Cephalosporium acremonium</p> Signup and view all the answers

    What is the benefit of categorizing cephalosporins by generation?

    <p>Easier to remember the properties of the many cephalosporins</p> Signup and view all the answers

    What is the name of the antibiotic class that cephalosporins belong to?

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

    What is the common feature of cephalosporins and penicillins?

    <p>Both are beta-lactam antibiotics</p> Signup and view all the answers

    What is the source of the first members of the cephalosporin class of antibiotics?

    <p>Cephalosporium acremonium</p> Signup and view all the answers

    What do cephalosporins and penicillins have in common?

    <p>They are both beta-lactam antibiotics</p> Signup and view all the answers

    What is the common feature of the structure of cephalosporins?

    <p>They have a nucleus with two side chains</p> Signup and view all the answers

    What is the benefit of categorizing cephalosporins by generation?

    <p>It helps to predict their antibacterial spectrum</p> Signup and view all the answers

    What is the name of the antibiotic class that cephalosporins belong to?

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

    What is the characteristic of cephalosporins that allows them to be categorized by generation?

    <p>Their antibacterial spectrum</p> Signup and view all the answers

    What is the common feature of cephalosporins and penicillins?

    <p>They are both beta-lactam antibiotics</p> Signup and view all the answers

    What is the categorization scheme used to organize cephalosporins?

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

    What is the primary addition that extends the activity of extended-spectrum penicillins to include most enteric gram-negative bacilli?

    <p>A -lactamase inhibitor</p> Signup and view all the answers

    Which type of bacteria are natural penicillins moderately active against?

    <p>Anaerobic bacteria</p> Signup and view all the answers

    What is the primary mechanism of action of penicillins?

    <p>Binding to bacterial enzymes that assemble peptidoglycan</p> Signup and view all the answers

    What is the primary advantage of aminopenicillins over natural penicillins?

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

    Which bacteria do not make peptidoglycan and therefore are not affected by the natural penicillins?

    <p>Mycoplasma spp.</p> Signup and view all the answers

    Which type of bacteria is P. aeruginosa?

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

    What is the main reason why some bacteria are resistant to natural penicillins?

    <p>They produce enzymes that break down penicillins.</p> Signup and view all the answers

    Which bacteria remain susceptible to penicillin despite being gram-negative?

    <p>Neisseria meningitidis</p> Signup and view all the answers

    What is the primary feature of extended-spectrum penicillins?

    <p>Activity against P. aeruginosa</p> Signup and view all the answers

    What is the result of combining extended-spectrum penicillins with -lactamase inhibitors?

    <p>Activity against most aerobic gram-negative bacteria, aerobic gram-positive bacteria, and anaerobes</p> Signup and view all the answers

    What is the characteristic of antistaphylococcal penicillins that makes them effective against staphylococcal infections?

    <p>They are resistant to beta-lactamases.</p> Signup and view all the answers

    What is the primary function of the bacterial enzymes that penicillins bind to?

    <p>To assemble peptidoglycan</p> Signup and view all the answers

    Which of the following bacteria is NOT affected by natural penicillins due to the production of penicillinases?

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

    What is the main difference between natural penicillins and antistaphylococcal penicillins?

    <p>Antistaphylococcal penicillins are resistant to beta-lactamases.</p> Signup and view all the answers

    Which of the following bacteria is susceptible to natural penicillins despite being anaerobic?

    <p>Actinomyces israelii</p> Signup and view all the answers

    What is the common feature of the bacteria that are susceptible to natural penicillins?

    <p>They all have a peptidoglycan layer in their cell walls.</p> Signup and view all the answers

    Study Notes

    Penicillins

    • Act by binding to PBPs, which are bacterial enzymes that function to assemble peptidoglycan.
    • Natural penicillins have moderate activity against aerobic gram-positive bacteria and anaerobic bacteria, but poor activity against aerobic gram-negative bacteria and most atypical bacteria.
    • Limitations of natural penicillins include:
      • Producing penicillinases that degrade natural penicillins (e.g., some anaerobes, such as Bacteroides fragilis).
      • Some bacteria produce PBPs that do not bind natural penicillins with high affinity (e.g., some strains of Streptococcus pneumoniae).
      • Some bacteria do not make peptidoglycan and are not affected by natural penicillins (e.g., Mycoplasma and Chlamydia spp.).

    Antistaphylococcal Penicillins

    • Have bulky residues on their R side chains that prevent binding by staphylococcal β-lactamases.
    • Useful in treating infections caused by S. aureus and Staphylococcus epidermidis, but not effective against methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE).

    Extended-Spectrum Penicillins

    • Active against even more enteric gram-negative rods and importantly, Pseudomonas aeruginosa.
    • Addition of a β-lactamase inhibitor to an extended-spectrum penicillin extends its activity to include most enteric gram-negative bacilli.

    Cephalosporins

    • Constitute a large extended family of antibiotics within the β-lactam group.
    • Can be categorized by "generation", with each generation having similar spectra of activity.
    • Each cephalosporin is composed of a nucleus with two side chains.

    Penicillins

    • Act by binding to PBPs, which are bacterial enzymes that function to assemble peptidoglycan.
    • Natural penicillins have moderate activity against aerobic gram-positive bacteria and anaerobic bacteria, but poor activity against aerobic gram-negative bacteria and most atypical bacteria.
    • Limitations of natural penicillins include:
      • Producing penicillinases that degrade natural penicillins (e.g., some anaerobes, such as Bacteroides fragilis).
      • Some bacteria produce PBPs that do not bind natural penicillins with high affinity (e.g., some strains of Streptococcus pneumoniae).
      • Some bacteria do not make peptidoglycan and are not affected by natural penicillins (e.g., Mycoplasma and Chlamydia spp.).

    Antistaphylococcal Penicillins

    • Have bulky residues on their R side chains that prevent binding by staphylococcal β-lactamases.
    • Useful in treating infections caused by S. aureus and Staphylococcus epidermidis, but not effective against methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE).

    Extended-Spectrum Penicillins

    • Active against even more enteric gram-negative rods and importantly, Pseudomonas aeruginosa.
    • Addition of a β-lactamase inhibitor to an extended-spectrum penicillin extends its activity to include most enteric gram-negative bacilli.

    Cephalosporins

    • Constitute a large extended family of antibiotics within the β-lactam group.
    • Can be categorized by "generation", with each generation having similar spectra of activity.
    • Each cephalosporin is composed of a nucleus with two side chains.

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    Learn about the mechanism of action of penicillins, their activity against various bacteria, and their limitations. Understand how penicillinases and PBPs affect their efficacy.

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