Dr. Nada M Nass: Bacterial Ribosomes and Protein Synthesis Inhibition
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Questions and Answers

What is the mechanism of action of tetracyclines?

  • Causing misreading of messenger RNA (mRNA)
  • Inhibiting DNA replication in bacterial cells
  • Preventing binding of amino-acyl transfer RNA (tRNA) to the ribosome (correct)
  • Preventing protein synthesis by inhibiting ribosomal initiation complex formation

    • Which statement about tigecycline is true?

  • It is ineffective against Gram-positive bacteria
  • It retains activity against many bacteria susceptible to other tetracyclines (correct)
  • It has limited activity against chlamediae and rickettsiae
  • It works by inhibiting the formation of ribosomal initiation complex

    • What is the main limitation that resistance has imposed on tetracyclines?

  • Prevention of binding amino-acyl transfer RNA (tRNA) to the ribosome
  • Limited value against many Gram-positive and Gram-negative bacteria (correct)
  • Decreased ability to cause misreading of mRNA
  • Reduced effectiveness against chlamydia and rickettsia

    • Which antibiotic acts by interfering with the action of bacterial dihydrofolate reductase?

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

    What is the enzyme that catalyzes the last step of bacterial folic acid synthesis?

    <p>Dihydrofolate reductase</p> Signup and view all the answers

    Which bacterial species are usually susceptible to tetracyclines despite resistance seen in others?

    <p>Chlamydia, rickettsia, and mycoplasmas</p> Signup and view all the answers

    Which antibiotic is a structural analog of para aminobenzoic acid (PABA) and competes with it to bind to dihydropterote synthetase?

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

    What is a notable side effect associated with aminoglycosides?

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

    Which antibiotics exhibit potent antipseudomonal activity but have limited usefulness due to toxicity?

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

    What type of effect arises between sulphonamides and trimethoprim when used in combination?

    <p>Synergistic effect</p> Signup and view all the answers

    Which antibiotic has a role in the treatment of infections caused by multidrug-resistant organisms?

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

    How do macrolide antibiotics act?

    <p>By interfering with the translocation of mRNA on the bacterial ribosome (binding to the 50S ribosome)</p> Signup and view all the answers

    What is the mechanism of action of chloramphenicol?

    <p>Blocking the growth of peptide chain</p> Signup and view all the answers

    Which antibiotic has been limited in use due to the occurrence of rare but fatal side effects like aplastic anemia?

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

    What is the primary target of fusidic acid in bacterial cells?

    <p>Factor G involved in peptide elongation</p> Signup and view all the answers

    Which organism is NOT sensitive to macrolide antibiotics?

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

    Resistance to antibiotics can arise from alterations in:

    <p>mRNA translocation on the bacterial ribosome</p> Signup and view all the answers

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