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?

Escherichia coli Signup and view all the answers

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

1991 Signup and view all the answers

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

'P' site Signup and view all the answers

What is the type of protein synthesis inhibited by macrolides?

RNA-dependent Signup and view all the answers

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

Treatment of tuberculosis Signup and view all the answers

What is the name of the bacterium that produces erythromycin?

Streptomyces erythreus Signup and view all the answers

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

Mild severity due to Streptococcus pneumoniae or Haemophilus influenzae Signup and view all the answers

What is the mechanism of epigastric distress caused by erythromycin?

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

Which of the following is NOT an indication for clarithromycin?

Disseminated Mycobacterium avium complex disease Signup and view all the answers

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

Non-gonococcal urethritis due to Chlamydia trachomatis 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?

Erythromycin Signup and view all the answers

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

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

What is the mechanism of action of macrolides?

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

Which of the following organisms is NOT susceptible to azithromycin?

Streptococcus aureus Signup and view all the answers

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

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

Which of the following statements regarding motilin activation is INCORRECT?

It is a common side effect of erythromycin. Signup and view all the answers

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

Cholestatic jaundice Signup and view all the answers

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

Hypersensitivity reaction to the estolate molecule Signup and view all the answers

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

QT prolongation Signup and view all the answers

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

Development of antibiotic resistance in bacteria Signup and view all the answers

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

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

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

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

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

Lower risk of QT prolongation Signup and view all the answers

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

Azithromycin is a semisynthetic derivative of erythromycin with a broader spectrum of activity. 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?

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

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

Bronchospasm 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?

Neutropenia Signup and view all the answers

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

Both drugs act by inhibiting the synthesis of bacterial cell wall peptidoglycans. 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?

Vancomycin Signup and view all the answers

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

Gentamicin is used as an adjunct therapy to vancomycin in treating enterococcal endocarditis. 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?

Metronidazole 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?

Monitoring of serum creatinine levels Signup and view all the answers

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

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

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

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

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

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

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

D-alanyl-D-alanine (D-Ala-D-Ala) terminal end Signup and view all the answers

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

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

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

They are bactericidal, directly killing bacterial cells. 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?

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

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

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

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

They are poorly absorbed from the gastrointestinal tract. Signup and view all the answers

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

They can have significant side effects, such as nephrotoxicity and ototoxicity. 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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Description

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