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Questions and Answers
What is the primary mechanism of action of macrolides?
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?
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?
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?
Which of the following organisms is NOT typically susceptible to erythromycin?
What is the year in which azithromycin and clarithromycin were brought to market?
What is the year in which azithromycin and clarithromycin were brought to market?
What is the site of action of macrolides on the ribosome?
What is the site of action of macrolides on the ribosome?
What is the type of protein synthesis inhibited by macrolides?
What is the type of protein synthesis inhibited by macrolides?
Which of the following is NOT a therapeutic use of erythromycin?
Which of the following is NOT a therapeutic use of erythromycin?
What is the name of the bacterium that produces erythromycin?
What is the name of the bacterium that produces erythromycin?
What is the indication for azithromycin in community-acquired pneumonia?
What is the indication for azithromycin in community-acquired pneumonia?
What is the mechanism of epigastric distress caused by erythromycin?
What is the mechanism of epigastric distress caused by erythromycin?
Which of the following is NOT an indication for clarithromycin?
Which of the following is NOT an indication for clarithromycin?
What is the primary indication for azithromycin in urethritis and cervicitis?
What is the primary indication for azithromycin in urethritis and cervicitis?
Which antibiotic is used as an adjunct to antitoxin to prevent establishment of carriers and to eradicate the organism in carriers of Corynebacterium diphtheriae?
Which antibiotic is used as an adjunct to antitoxin to prevent establishment of carriers and to eradicate the organism in carriers of Corynebacterium diphtheriae?
What is the indication for azithromycin in acute bacterial exacerbations of chronic obstructive pulmonary disease?
What is the indication for azithromycin in acute bacterial exacerbations of chronic obstructive pulmonary disease?
What is the mechanism of action of macrolides?
What is the mechanism of action of macrolides?
Which of the following organisms is NOT susceptible to azithromycin?
Which of the following organisms is NOT susceptible to azithromycin?
What is the indication for clarithromycin in community-acquired pneumonia?
What is the indication for clarithromycin in community-acquired pneumonia?
Which of the following statements regarding motilin activation is INCORRECT?
Which of the following statements regarding motilin activation is INCORRECT?
Which of the following is a unique side effect associated with the estolate form of erythromycin?
Which of the following is a unique side effect associated with the estolate form of erythromycin?
What is the primary mechanism responsible for the cholestatic jaundice associated with erythromycin estolate?
What is the primary mechanism responsible for the cholestatic jaundice associated with erythromycin estolate?
Which of the following side effects is NOT specifically associated with the estolate salt of erythromycin?
Which of the following side effects is NOT specifically associated with the estolate salt of erythromycin?
Which of the following is a potential risk associated with the use of erythromycin?
Which of the following is a potential risk associated with the use of erythromycin?
Which of the following correctly describes the relationship between erythromycin and azithromycin?
Which of the following correctly describes the relationship between erythromycin and azithromycin?
What does the term 'cross-resistance' imply in the context of erythromycin and azithromycin?
What does the term 'cross-resistance' imply in the context of erythromycin and azithromycin?
Which of the following is NOT a characteristic of azithromycin compared to erythromycin?
Which of the following is NOT a characteristic of azithromycin compared to erythromycin?
Which of the following statements about azithromycin is TRUE based on the provided content?
Which of the following statements about azithromycin is TRUE based on the provided content?
Which of the following statements is TRUE regarding the use of vancomycin in pseudomembranous enterocolitis (PMC) caused by Clostridium difficile?
Which of the following statements is TRUE regarding the use of vancomycin in pseudomembranous enterocolitis (PMC) caused by Clostridium difficile?
Which of the following is a known adverse effect of teicoplanin, but NOT of vancomycin?
Which of the following is a known adverse effect of teicoplanin, but NOT of vancomycin?
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?
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?
Considering the mechanism of action of vancomycin and teicoplanin, which of the following statements is CORRECT?
Considering the mechanism of action of vancomycin and teicoplanin, which of the following statements is CORRECT?
A patient is diagnosed with methicillin-resistant Staphylococcus aureus (MRSA) infection. Which of the following antibiotics would be most appropriate for treating this infection?
A patient is diagnosed with methicillin-resistant Staphylococcus aureus (MRSA) infection. Which of the following antibiotics would be most appropriate for treating this infection?
Which of the following statements is TRUE regarding the use of gentamicin in enterococcal endocarditis?
Which of the following statements is TRUE regarding the use of gentamicin in enterococcal endocarditis?
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?
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?
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?
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?
Which of the following scenarios would necessitate the use of teicoplanin over vancomycin?
Which of the following scenarios would necessitate the use of teicoplanin over vancomycin?
What is the primary mechanism by which vancomycin and teicoplanin exert their bactericidal effect?
What is the primary mechanism by which vancomycin and teicoplanin exert their bactericidal effect?
Why are vancomycin and teicoplanin ineffective against Gram-negative bacteria?
Why are vancomycin and teicoplanin ineffective against Gram-negative bacteria?
What is the target site of vancomycin and teicoplanin on the peptidoglycan molecule?
What is the target site of vancomycin and teicoplanin on the peptidoglycan molecule?
Which of the following statements accurately describes the action of vancomycin and teicoplanin on bacterial cells?
Which of the following statements accurately describes the action of vancomycin and teicoplanin on bacterial cells?
Which of the following is a characteristic of the mechanism of action of vancomycin and teicoplanin?
Which of the following is a characteristic of the mechanism of action of vancomycin and teicoplanin?
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?
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?
How does the binding of vancomycin and teicoplanin to the peptidoglycan molecule affect the bacterial cell?
How does the binding of vancomycin and teicoplanin to the peptidoglycan molecule affect the bacterial cell?
What is the primary reason vancomycin and teicoplanin are given intravenously?
What is the primary reason vancomycin and teicoplanin are given intravenously?
What is a major disadvantage of using vancomycin and teicoplanin for treating bacterial infections?
What is a major disadvantage of using vancomycin and teicoplanin for treating bacterial infections?
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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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