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Questions and Answers
What is the primary mechanism of action of glycopeptides?
What is the primary mechanism of action of glycopeptides?
- Inhibition of protein synthesis
- Disruption of the bacterial cell membrane potential
- Interference with DNA replication
- Inhibition of cell wall synthesis (correct)
Which types of bacteria are glycopeptides effective against?
Which types of bacteria are glycopeptides effective against?
- Gram-positive anaerobes
- All types of bacteria
- Gram-negative bacteria
- Gram-positive cocci (correct)
What is a common indication for the use of vancomycin?
What is a common indication for the use of vancomycin?
- Meningitis caused by penicillin-sensitive bacteria
- Treatment of viral infections
- Fungal infections
- Septicemia caused by MRSA (correct)
What is the resistance mechanism to vancomycin in enterococci?
What is the resistance mechanism to vancomycin in enterococci?
Which of the following bacteria is not targeted effectively by glycopeptides?
Which of the following bacteria is not targeted effectively by glycopeptides?
What is the effect of glycopeptides on bacterial cell membranes?
What is the effect of glycopeptides on bacterial cell membranes?
Which combination is commonly used for treating endocarditis caused by enterococci?
Which combination is commonly used for treating endocarditis caused by enterococci?
What is NOT an indication for oral administration of vancomycin?
What is NOT an indication for oral administration of vancomycin?
What is a significant adverse effect associated with certain antimicrobial therapies?
What is a significant adverse effect associated with certain antimicrobial therapies?
Which glycopeptide is NOT mentioned as a member of the class?
Which glycopeptide is NOT mentioned as a member of the class?
What mechanism does fosfomycin use to inhibit bacterial growth?
What mechanism does fosfomycin use to inhibit bacterial growth?
What is the consequence of vancomycin binding affinity loss due to resistance?
What is the consequence of vancomycin binding affinity loss due to resistance?
Which of the following is an indication for using telavancin?
Which of the following is an indication for using telavancin?
What condition can be prevented by slow infusion or pretreatment with antihistamines?
What condition can be prevented by slow infusion or pretreatment with antihistamines?
Which of the following statements is true regarding teicoplanin?
Which of the following statements is true regarding teicoplanin?
What is a limitation of fosfomycin's use in treating severe infections?
What is a limitation of fosfomycin's use in treating severe infections?
Which type of organisms is fosfomycin effective against?
Which type of organisms is fosfomycin effective against?
What is a critical monitoring aspect while using certain antimicrobials?
What is a critical monitoring aspect while using certain antimicrobials?
Which bacterial strain is fosfomycin particularly effective against?
Which bacterial strain is fosfomycin particularly effective against?
Which statement accurately reflects the antibacterial spectrum of teicoplanin?
Which statement accurately reflects the antibacterial spectrum of teicoplanin?
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Study Notes
Glycopeptides
- Glycopeptides are bactericidal against Gram-positive bacteria.
- Glycopeptides do not penetrate the cell membrane of Gram-negative bacteria due to their large molecular weight and hydrophilic nature.
- They inhibit cell wall synthesis by binding to D-Ala-D-Ala terminus of a growing peptidoglycan pentapeptide.
- This binding inhibits the transglycosylase enzyme which stops the elongation and cross-linking of peptidoglycan.
- They can increase membrane permeability and disrupt bacterial cell membrane potential.
Glycopeptide Antibacterial Spectrum
- Glycopeptides are mainly active against Gram-positive cocci like staphylococci, streptococci, and enterococci.
- They can display synergistic activity with gentamicin and streptomycin against enterococci (E. faecium and E. faecalis).
- They are also active against Gram-positive anaerobes, including C. difficile.
- They are not active against Gram-negative bacteria.
Glycopeptide Examples
- Includes vancomycin, teicoplanin, and telavancin.
Vancomycin
- Mainly given intravenously.
- Indicated for septicemia, endocarditis (caused by MRSA and enterococci), meningitis, and enterocolitis.
- Combined with gentamicin when used for endocarditis in patients with penicillin allergy.
- Given orally for C. difficile enterocolitis.
Vancomycin Resistance
- Resistance in enterococci stems from modification of the D-Ala-D-Ala binding site.
- Terminal D-Ala is replaced by D-lactate, leading to loss of hydrogen bond that facilitates vancomycin binding.
- This results in loss of vancomycin activity.
- This mechanism is also present in rare vancomycin-resistant S. aureus strains.
Vancomycin Adverse Effects
- Phlebitis at injection site.
- Nephrotoxicity (requires monitoring).
- Ototoxicity (rare).
- Red man syndrome (prevented by slow infusion or oral antihistamine pretreatment).
Teicoplanin
- Similar antibacterial spectrum and clinical indications to vancomycin.
- Active against vancomycin-resistant S. aureus.
- Shows higher activity against enterococci than vancomycin.
Telavancin
- Similar antibacterial spectrum to vancomycin.
- Approved for complicated skin and soft tissue infections and hospital-acquired pneumonia.
Fosfomycin
- Broad-spectrum antibiotic.
- Active against extended spectrum β-lactamase-producing (ESBL) E. coli.
- Limited use in severe infections due to resistance related to lack of drug transport into the cell.
Fosfomycin Antibacterial Spectrum
- Active against both Gram-positive and Gram-negative organisms including E. coli and E. faecalis.
Fosfomycin Mechanism of Action
- Inhibits an early stage of bacterial cell wall synthesis.
- Inhibits the enzyme enolpyruvate transferase by acting as an analog of phosphoenolpyruvate.
- This enzyme is responsible for forming N-acetylmuramic acid, a key component of peptidoglycan.
Fosfomycin Indications
- Uncomplicated lower urinary tract infections in women (safe during pregnancy).
- Given as a single 3-g dose tablet.
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