Macrolides Antibiotics
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Questions and Answers

What is the primary mechanism of action of macrolides?

  • By enhancing the breakdown of bacterial cell walls
  • By inhibiting protein synthesis at the translation stage
  • By inhibiting DNA-dependent RNA synthesis
  • By reversibly binding to the 'P' site of 50S ribosomal subunits (correct)

    • What is the effect of macrolides on bacteria at therapeutic doses?

  • Bacteriostatic (correct)
  • Fungicidal
  • Bactericidal
  • Virucidal

    • What is erythromycin used as an alternate to in the treatment of syphilis?

  • Ciprofloxacin
  • Tetracycline
  • Penicillin G (correct)
  • Amoxicillin

    • Which of the following organisms is NOT typically susceptible to erythromycin?

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

    What is the year in which azithromycin and clarithromycin were brought to market?

    <p>1991</p> Signup and view all the answers

    What is the site of action of macrolides on the ribosome?

    <p>'P' site</p> Signup and view all the answers

    What is the type of protein synthesis inhibited by macrolides?

    <p>RNA-dependent</p> Signup and view all the answers

    Which of the following is NOT a therapeutic use of erythromycin?

    <p>Treatment of tuberculosis</p> Signup and view all the answers

    What is the name of the bacterium that produces erythromycin?

    <p>Streptomyces erythreus</p> Signup and view all the answers

    What is the indication for azithromycin in community-acquired pneumonia?

    <p>Mild severity due to Streptococcus pneumoniae or Haemophilus influenzae</p> Signup and view all the answers

    What is the mechanism of epigastric distress caused by erythromycin?

    <p>Formation of a hemiketal intermediate, a motilin-receptor agonist</p> Signup and view all the answers

    Which of the following is NOT an indication for clarithromycin?

    <p>Disseminated Mycobacterium avium complex disease</p> Signup and view all the answers

    What is the primary indication for azithromycin in urethritis and cervicitis?

    <p>Non-gonococcal urethritis due to Chlamydia trachomatis</p> Signup and view all the answers

    Which antibiotic is used as an adjunct to antitoxin to prevent establishment of carriers and to eradicate the organism in carriers of Corynebacterium diphtheriae?

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

    What is the indication for azithromycin in acute bacterial exacerbations of chronic obstructive pulmonary disease?

    <p>Due to Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae</p> Signup and view all the answers

    What is the mechanism of action of macrolides?

    <p>Inhibition of protein synthesis by binding to the 50S ribosomal subunit</p> Signup and view all the answers

    Which of the following organisms is NOT susceptible to azithromycin?

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

    What is the indication for clarithromycin in community-acquired pneumonia?

    <p>Due to Haemophilus influenzae, Mycoplasma pneumoniae, Streptococcus pneumoniae, or Chlamydia pneumoniae</p> Signup and view all the answers

    Which of the following statements regarding motilin activation is INCORRECT?

    <p>It is a common side effect of erythromycin.</p> Signup and view all the answers

    Which of the following is a unique side effect associated with the estolate form of erythromycin?

    <p>Cholestatic jaundice</p> Signup and view all the answers

    What is the primary mechanism responsible for the cholestatic jaundice associated with erythromycin estolate?

    <p>Hypersensitivity reaction to the estolate molecule</p> Signup and view all the answers

    Which of the following side effects is NOT specifically associated with the estolate salt of erythromycin?

    <p>QT prolongation</p> Signup and view all the answers

    Which of the following is a potential risk associated with the use of erythromycin?

    <p>Development of antibiotic resistance in bacteria</p> Signup and view all the answers

    Which of the following correctly describes the relationship between erythromycin and azithromycin?

    <p>Azithromycin is a derivative of erythromycin with a broader spectrum of activity.</p> Signup and view all the answers

    What does the term 'cross-resistance' imply in the context of erythromycin and azithromycin?

    <p>Bacteria resistant to erythromycin are also likely to be resistant to azithromycin.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of azithromycin compared to erythromycin?

    <p>Lower risk of QT prolongation</p> Signup and view all the answers

    Which of the following statements about azithromycin is TRUE based on the provided content?

    <p>Azithromycin is a semisynthetic derivative of erythromycin with a broader spectrum of activity.</p> Signup and view all the answers

    Which of the following statements is TRUE regarding the use of vancomycin in pseudomembranous enterocolitis (PMC) caused by Clostridium difficile?

    <p>Vancomycin is only used in severe cases of PMC when metronidazole is ineffective.</p> Signup and view all the answers

    Which of the following is a known adverse effect of teicoplanin, but NOT of vancomycin?

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

    A patient is experiencing severe chills and fever along with a rash. The patient's medical history indicates a recent course of vancomycin therapy. Which of the following adverse effects is most likely responsible for these symptoms?

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

    Considering the mechanism of action of vancomycin and teicoplanin, which of the following statements is CORRECT?

    <p>Both drugs act by inhibiting the synthesis of bacterial cell wall peptidoglycans.</p> Signup and view all the answers

    A patient is diagnosed with methicillin-resistant Staphylococcus aureus (MRSA) infection. Which of the following antibiotics would be most appropriate for treating this infection?

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

    Which of the following statements is TRUE regarding the use of gentamicin in enterococcal endocarditis?

    <p>Gentamicin is used as an adjunct therapy to vancomycin in treating enterococcal endocarditis.</p> Signup and view all the answers

    A patient presents with severe diarrhea and abdominal pain. The patient's medical history reveals a recent course of antibiotic therapy. The physician suspects Clostridium difficile infection. Which of the following antibiotics would be the most appropriate first-line treatment?

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

    A patient with a history of severe renal impairment is prescribed vancomycin. Which of the following monitoring strategies is most crucial to ensure safe and effective therapy in this patient?

    <p>Monitoring of serum creatinine levels</p> Signup and view all the answers

    Which of the following scenarios would necessitate the use of teicoplanin over vancomycin?

    <p>Treatment of a patient with MRSA infection and a history of severe vancomycin-induced nephrotoxicity.</p> Signup and view all the answers

    What is the primary mechanism by which vancomycin and teicoplanin exert their bactericidal effect?

    <p>They prevent the synthesis of peptidoglycan, a key component of the bacterial cell wall.</p> Signup and view all the answers

    Why are vancomycin and teicoplanin ineffective against Gram-negative bacteria?

    <p>They are unable to penetrate the outer membrane of Gram-negative bacteria.</p> Signup and view all the answers

    What is the target site of vancomycin and teicoplanin on the peptidoglycan molecule?

    <p>D-alanyl-D-alanine (D-Ala-D-Ala) terminal end</p> Signup and view all the answers

    Which of the following statements accurately describes the action of vancomycin and teicoplanin on bacterial cells?

    <p>They prevent the formation of a functional cell wall, leading to bacterial cell death.</p> Signup and view all the answers

    Which of the following is a characteristic of the mechanism of action of vancomycin and teicoplanin?

    <p>They are bactericidal, directly killing bacterial cells.</p> Signup and view all the answers

    What is the significance of the D-alanyl-D-alanine (D-Ala-D-Ala) terminal end of the peptidoglycan molecule in the context of vancomycin and teicoplanin action?

    <p>It is the site where vancomycin and teicoplanin bind, disrupting the synthesis of peptidoglycan.</p> Signup and view all the answers

    How does the binding of vancomycin and teicoplanin to the peptidoglycan molecule affect the bacterial cell?

    <p>It prevents the formation of a complete and functional cell wall, leading to cell lysis.</p> Signup and view all the answers

    What is the primary reason vancomycin and teicoplanin are given intravenously?

    <p>They are poorly absorbed from the gastrointestinal tract.</p> Signup and view all the answers

    What is a major disadvantage of using vancomycin and teicoplanin for treating bacterial infections?

    <p>They can have significant side effects, such as nephrotoxicity and ototoxicity.</p> Signup and view all the answers

    Study Notes

    Macrolides

    • Macrolides are a widely used class of antibiotics.
    • Erythromycin was the first macrolide, isolated in 1952 from Streptomyces erythreus.
    • Semisynthetic derivatives azithromycin and clarithromycin were introduced in 1991.
    • Common macrolides include erythromycin, clarithromycin, azithromycin, and roxithromycin.
    • Mechanism of action involves reversible binding to the ‘P’ site of 50S ribosomal subunits, inhibiting RNA-dependent protein synthesis.
    • Macrolides are generally bacteriostatic, but can become bactericidal at higher doses.

    Therapeutic Uses of Macrolides

    • Erythromycin:
      • Effective against many organisms similar to penicillin G; used for penicillin-allergic patients.
      • Prophylaxis for bacterial endocarditis, syphilis treatment, and various respiratory infections.
    • Azithromycin:
      • Treats acute bacterial exacerbations of chronic obstructive pulmonary disease (COPD).
      • Used for community-acquired pneumonia, streptococcal pharyngitis, non-gonococcal urethritis, and disseminated Mycobacterium avium complex.
    • Clarithromycin:
      • Indicated for pharyngitis, acute maxillary sinusitis, bronchitis exacerbations, acute otitis media, and community-acquired pneumonia.

    Adverse Effects of Erythromycin

    • Commonly causes epigastric distress due to its degradation in the stomach, leading to abdominal discomfort and diarrhea.
    • Cholestatic jaundice is primarily seen with the estolate form due to hypersensitivity reactions.
    • Hypersensitivity reactions may present as skin rashes, fever, or eosinophilia.
    • Associated with QT prolongation, potentially resulting in serious ventricular arrhythmias.

    Comparison of Erythromycin and Azithromycin

    • Azithromycin, a semisynthetic derivative of erythromycin, exhibits a broader spectrum of activity.
    • Azithromycin shares cross-resistance with erythromycin.

    Glycopeptide Antibiotics

    • Vancomycin and teicoplanin have a similar mechanistic action and are bactericidal.
    • They inhibit cell wall synthesis by binding to the D-alanyl-D-alanine portion of the peptidoglycan pentapeptide.
    • This binding prevents elongation and cross-linking of peptidoglycan layers, causing cell wall defects, fluid entry, and bacterial lysis.
    • Both antibiotics are ineffective against gram-negative organisms due to their large molecular size.

    Uses and Adverse Effects of Glycopeptide Antibiotics

    • Vancomycin:
      • Administered intravenously for enterococcal endocarditis, MRSA infections, and pseudomembranous enterocolitis.
      • Adverse effects include red man syndrome, ototoxicity, nephrotoxicity, rashes, and fever.
    • Teicoplanin:
      • Shares the same spectrum and uses as vancomycin.
      • Adverse effects may include bronchospasm.

    Important Clinical Considerations

    • Understanding the spectrum of activity, effectiveness, and potential side effects is crucial for appropriate antibiotic selection.
    • Regular monitoring is necessary for patients on prolonged macrolide therapy due to potential adverse effects.

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    Macrolides & Glycopeptide Antibiotics (2024) PDF

    Description

    Introduction to macrolides, their history, types and mechanism of action. Learn about erythromycin, clarithromycin, azithromycin and more.

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