Antibiotics: Mechanism and Effectiveness Quiz
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Questions and Answers

What is the mechanism of action for oxazolidinones like linezolid?

  • Inhibition of DNA synthesis
  • Interference with protein translation at the ribosome (correct)
  • Inhibition of RNA polymerase activity
  • Disruption of cell wall integrity

    • Which of the following bacterial strains are oxazolidinones effective against?

  • Clostridium difficile
  • Staphylococcus aureus (both MSSA and MRSA) (correct)
  • Escherichia coli
  • Pseudomonas aeruginosa

    • What should be monitored weekly while on therapy with certain antibacterial agents?

  • Liver enzymes
  • Serum creatinine
  • Serum CPK (correct)
  • Complete blood count (CBC)

    • Why are certain antibiotics not suitable for treating pneumonia?

    <p>Binding to human pulmonary surfactant</p> Signup and view all the answers

    What is the primary reason for the unique dosing parameters in treatment for Staphylococcus aureus in obese patients?

    <p>Increased volume of distribution</p> Signup and view all the answers

    What is the mechanism of action of dapto?

    <p>Binds to 23S portion of 50S ribosomal subunit</p> Signup and view all the answers

    What is a significant adverse effect associated with linezolid?

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

    What distinguishes telavancin from vancomycin?

    <p>Has a hydrophobic tail that enhances activity</p> Signup and view all the answers

    For what condition would ceftaroline be primarily indicated?

    <p>Infection caused by MRSA</p> Signup and view all the answers

    Which pharmacokinetic characteristic is NOT true for linezolid?

    <p>Predominantly eliminated by renal excretion</p> Signup and view all the answers

    Which of the following organisms is NOT susceptible to ceftaroline?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    What is true about the protein binding of telavancin?

    <p>90% protein bound</p> Signup and view all the answers

    What renal adjustment is necessary when using telavancin?

    <p>Monitor creatinine clearance and adjust accordingly</p> Signup and view all the answers

    Which condition is a common indication for linezolid?

    <p>Pneumonia caused by MSSA</p> Signup and view all the answers

    What is the most important side effect to monitor when using linezolid?

    <p>Serotonin syndrome</p> Signup and view all the answers

    What is the primary method of elimination for vancomycin?

    <p>Renal excretion</p> Signup and view all the answers

    What is the recommended serum trough concentration of vancomycin for serious infections?

    <p>15-20 mcg/ml</p> Signup and view all the answers

    What type of organisms is vancomycin effective against?

    <p>Gram-positive bacilli</p> Signup and view all the answers

    What mechanism makes vancomycin-resistant Staphylococcus (VRSA) rare?

    <p>VanA gene presence</p> Signup and view all the answers

    What is a significant adverse effect of daptomycin?

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

    Daptomycin is primarily indicated for treating which type of infections?

    <p>Complicated skin infections</p> Signup and view all the answers

    What is the mechanism of action (MOA) of daptomycin?

    <p>Disruption of cell membrane potential</p> Signup and view all the answers

    Which of the following is a contraindication for daptomycin use?

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

    What is the half-life (T1/2) of vancomycin?

    <p>4-6 hours</p> Signup and view all the answers

    Which condition significantly increases the risk of nephrotoxicity when using vancomycin?

    <p>Use of piperacillin/tazobactam</p> Signup and view all the answers

    What percentage of daptomycin is bound to serum proteins?

    <p>90%</p> Signup and view all the answers

    What is a notable characteristic of VISA?

    <p>Thickened cell wall</p> Signup and view all the answers

    How is daptomycin primarily excreted from the body?

    <p>Renal excretion</p> Signup and view all the answers

    Which of the following bacteria can be treated with daptomycin?

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

    Study Notes

    Vancomycin

    • Elimination: Primarily renal; 90% via glomerular filtration; altered renal function requires dose adjustments.
    • Pharmacokinetics: Half-life (T1/2) of 4-6 hours; constant monitoring needed for renal insufficiency.
    • Administration Routes: IV for systemic infections; oral administration limited to gut-targeting (C. difficile).
    • Nephrotoxicity: Historically linked to impure products; current understanding: exposure mitigates risk; ideal serum trough concentrations are 15-20 mcg/ml for serious infections.
    • Spectrum of Activity: Effective against gram-positive cocci and bacilli, including MRSA; ineffective against gram-negative organisms.

    Resistance and Susceptibility

    • Staphylococcal Resistance: Extremely rare; enterococcal resistance more common.
    • Susceptibility Guidelines:
      • Susceptible: ≤ 2 mcg/ml
      • Intermediate: 4-8 mcg/ml
      • Resistant: ≥ 16 mcg/ml (VISA and VRSA present)
    • VISA Mechanism: Thickened cell wall limits drug effectiveness; presents false binding sites.
    • VRSA Mechanism: Involves VanA gene from vancomycin-resistant Enterococcus; co-infections are common.

    Daptomycin

    • Classification: Semisynthetic cyclic lipopolypeptide derived from Streptomyces roseosporus.
    • Mechanism of Action: Disrupts cell membrane via calcium-mediated insertion.
    • Pharmacokinetics: Administered IV; T1/2 of 8-9 hours; highly protein-bound (90%); excreted renally.
    • Microbiology: Active against aerobic gram-positive organisms, including MRSA and vancomycin-resistant strains; ineffective against gram-negative bacteria.

    Indications and Concerns for Daptomycin

    • Indications: Complicated skin infections, bacteremia due to MSSA or MRSA, right-sided endocarditis.
    • Caveat: Inferior to ceftriaxone for pneumonia; inactivated by human lung surfactant.
    • Adverse Drug Events (ADEs): Injection reactions, gastrointestinal disturbances, central nervous system effects, and potential rhabdomyolysis.

    Oxazolidinones (Linezolid, Tedizolid)

    • Spectrum of Activity: Effective against aerobic gram-positive organisms, including resistant strains of enterococci and staphylococci.
    • Mechanism of Action: Inhibits protein synthesis by binding to the 50S ribosomal subunit.
    • Administration: Available IV and orally; oral bioavailability (BA) is 100%.
    • ADEs: Include thrombocytopenia, anemia, leukopenia; risk of serotonin syndrome, particularly when taken with serotonergic agents.

    Telavancin

    • Classification: Semisynthetic cyclic lipoglycopeptide, modified from vancomycin for improved efficacy.
    • Mechanism of Action: Similar to vancomycin, with enhanced cell wall disruption due to hydrophobic tail.
    • Approval and Pharmacology: Administered IV with a half-life of 8 hours; renal excretion with no routine therapeutic monitoring.
    • Signal of Mortality: Black box warning due to increased mortality noted in specific patient populations.

    Ceftaroline

    • Classification: Advanced generation cephalosporin sometimes referred to as 5th generation.
    • Activity: Active against MRSA through binding to low-affinity PBP 2a; limited effectiveness against gram-negative organisms.
    • Indication: Administered IV; T1/2 of 2.6 hours; renally eliminated and expensive.

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    Vancomycin & Daptomycin PDF

    Description

    Test your understanding of the mechanism of action of oxazolidinones like linezolid and their effectiveness against various bacterial strains. This quiz also covers monitoring requirements during therapy and the rationale behind unique dosing parameters for treating Staphylococcus aureus in obese patients. Evaluate your knowledge on the limitations of certain antibiotics in treating pneumonia.

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