Antibiotic Mechanisms: Nucleic Acid Synthesis Inhibition
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Questions and Answers

What is the mechanism of action of quinolones?

  • Inhibiting bacterial RNA polymerase
  • Inhibiting bacterial type II topoisomerases (DNA gyrase and topoisomerase IV) (correct)
  • Destructing microbial membranes
  • Inhibiting bacterial type I topoisomerases

    • Which generation of quinolones includes Levofloxacin and Tosufloxacin?

  • 1st generation
  • 4th generation
  • 2nd generation
  • 3rd generation (correct)

    • What is the mechanism of action of Rifampicin?

  • Inhibiting bacterial type II topoisomerases (DNA gyrase and topoisomerase IV)
  • Inhibiting bacterial type I topoisomerases
  • Inhibiting RNA polymerase (correct)
  • Destructing microbial membranes

    • Which of the following is NOT a mechanism of antibiotic action?

    <p>Stimulation of nucleic acid synthesis</p> Signup and view all the answers

    What is the target of nitroimidazoles?

    <p>DNA synthesis</p> Signup and view all the answers

    What is the mechanism of action of 4th generation quinolones?

    <p>Inhibiting bacterial type II topoisomerases (DNA gyrase and topoisomerase IV)</p> Signup and view all the answers

    What is the primary function of topoisomerase II (DNA gyrase) during normal transcription?

    <p>Relaxing supercoiled DNA</p> Signup and view all the answers

    Which of the following is a mechanism of quinolone resistance?

    <p>Mutations leading to an increased expression of efflux pumps</p> Signup and view all the answers

    Which generation of fluoroquinolones has enhanced activity against Gram-positive bacteria?

    <p>4th generation</p> Signup and view all the answers

    What is the primary target of nalidixic acid?

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

    Which of the following bacteria is NOT typically targeted by 2nd generation fluoroquinolones?

    <p>Streptococcus spp.</p> Signup and view all the answers

    What is the result of chromosomal mutations leading to reduced outer membrane permeability?

    <p>Reduced uptake of fluoroquinolones</p> Signup and view all the answers

    Which of the following is a characteristic of fluoroquinolones compared to nalidixic acid?

    <p>Longer half-life</p> Signup and view all the answers

    What is the mechanism of action of fluoroquinolones in inhibiting bacterial DNA synthesis?

    <p>Inhibiting topoisomerase II and IV</p> Signup and view all the answers

    What is the primary use of Gemifloxacin?

    <p>Treatment of acute bacterial exacerbation of chronic bronchitis</p> Signup and view all the answers

    What is a concern when combining Gemifloxacin with steroids?

    <p>Increased risk of tendon damage and tendon rupture</p> Signup and view all the answers

    What is a common side effect of Gemifloxacin?

    <p>All of the above</p> Signup and view all the answers

    Why is Gemifloxacin not recommended in pediatric patients?

    <p>Due to risk of cartilage toxicity and joint swelling</p> Signup and view all the answers

    What is a contraindication for Gemifloxacin?

    <p>Pregnancy category C</p> Signup and view all the answers

    What is a characteristic of Gemifloxacin compared to other fluoroquinolones?

    <p>Higher incidence of skin rash</p> Signup and view all the answers

    What is the elimination half-life of Gemifloxacin in patients with normal renal function?

    <p>6-8 hours</p> Signup and view all the answers

    What is a central nervous system side effect of Gemifloxacin?

    <p>All of the above</p> Signup and view all the answers

    Which of the following quinolone antibiotics is primarily eliminated by the hepatic route and does not require dosage adjustment in renal failure?

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

    Which of the following quinolones is not recommended for use in children and adolescents younger than 18 years of age due to the risk of cartilage damage and subsequent growth impairment?

    <p>Nalidixic acid</p> Signup and view all the answers

    Which of the following quinolone antibiotics is active against Pseudomonas aeruginosa?

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

    What is the primary reason for dosage adjustment of quinolone antibiotics in patients with renal insufficiency?

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

    Which of the following quinolones is used in the treatment of post-exposure prophylaxis for anthrax?

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

    Which of the following quinolones is primarily used in the treatment of uncomplicated urinary tract infections?

    <p>Nalidixic acid</p> Signup and view all the answers

    What is the primary reason for the impaired oral absorption of quinolone antibiotics?

    <p>Divalent cations</p> Signup and view all the answers

    Which of the following quinolones is classified as a 1st generation quinolone?

    <p>Nalidixic acid</p> Signup and view all the answers

    What is the primary indication for Ciprofloxacin in relation to Bacillus anthracis?

    <p>Postexposure prophylaxis for treatment of anthrax</p> Signup and view all the answers

    Which of the following fluoroquinolones has the longest half-life?

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

    Which generation of fluoroquinolones is characterized by extended Gram positive and atypical coverage?

    <p>3rd generation</p> Signup and view all the answers

    What is the primary indication for Levofloxacin in relation to Mycobacterium tuberculosis?

    <p>Second-line antitubercular therapy</p> Signup and view all the answers

    Which of the following fluoroquinolones is known for its broad antibacterial spectrum and higher antibacterial power than other fluoroquinolones?

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

    Which of the following bacteria is NOT covered by 3rd generation fluoroquinolones?

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

    What is the primary indication for Ofloxacin in relation to Neisseria gonorrhoeae?

    <p>Treatment of cervical infections</p> Signup and view all the answers

    Which of the following fluoroquinolones is classified as a respiratory quinolone?

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

    Study Notes

    Inhibitors of Nucleic Acid Synthesis

    • Inhibitors of DNA replication: Quinolones, Nitroimidazoles
    • Inhibitors of RNA polymerase: Rifampicin

    Quinolones

    • Target DNA synthesis by interfering with the coiling of DNA strands through inhibiting bacterial type II topoisomerases (DNA gyrase and topoisomerase IV)
    • Interfere with bacterial DNA synthesis by inhibiting two important enzymes: Topoisomerases II (DNA gyrase) and Topoisomerases IV
    • Mechanism of action: relaxing supercoiled DNA during normal transcription and separation of chromosomal DNA during cell division

    Generations of Quinolones

    • 1st generation: Nalidixic acid
      • Active against some gram-negative bacteria (E.coli, Salmonella, Shigella, Klebsiella)
      • Attains high concentration in urine; mostly used in uncomplicated urinary tract infections
      • Not recommended for children or adolescents younger than 18 years due to the risk of cartilage damage and growth impairment
    • 2nd generation: Ciprofloxacin, Norfloxacin, Ofloxacin
      • Improved activity against Gram-negative bacteria, some Gram-positive bacteria, and atypicals
      • Enterobacteriaceae, Pseudomonas aeruginosa, Haemophilus influenzae, Neisseria spp., Chlamydia spp., and Legionella spp.
    • 3rd generation: Levofloxacin
      • Active against Gram-negative bacteria and extended Gram-positive and atypical coverage
      • Streptococcus spp., including S.pneumoniae, methicillin-susceptible Staphylococcus aureus, Stenotrophomonas maltophilia, and Mycobacterium spp.
    • 4th generation: Delafloxacin, Moxifloxacin, Gemifloxacin
      • Delafloxacin: broad antibacterial spectrum, higher antibacterial power than other fluoroquinolones
      • Gemifloxacin: used for acute bacterial exacerbation of chronic bronchitis and mild to moderate community-acquired pneumonia

    Mechanism of Quinolone Resistance

    • Mutations in the bacterial chromosomal genes encoding DNA gyrase or topoisomerase IV
    • Chromosomal mutations leading to reduced outer membrane permeability
    • Mutations leading to an increased expression of efflux pumps
    • Biofilm production

    Pharmacokinetic Properties of Quinolones

    • Well absorbed after oral administration
    • Oral absorption impaired by divalent cations (Antiacids containing Mg, Ca, Al)
    • Widely distributed in body tissues
    • Pass placenta, reach the fetus
    • Most eliminated by renal (except Moxifloxacin and Pefloxacin); dosage adjustment required in patients with renal insufficiency

    Therapeutic Uses of Quinolones

    • Urinary Tract Infections (UTIs)
    • Respiratory Tract Infections
    • Skin and Soft Tissue Infections
    • Sexually Transmitted Infections (STIs)
    • Bone and Joint Infections
    • Gastrointestinal Infections
    • Post-exposure Prophylaxis for Anthrax

    Side Effects of Quinolones

    • Tendon damage and tendon rupture, especially if combined with steroids
    • Prolongation of QT intervals
    • Skin rash and photosensitivity
    • Primarily gastrointestinal, with nausea and vomiting
    • Unpleasant taste
    • Allergic Reactions: Rashes, hives, and anaphylaxis
    • CNS reactions to insomnia and increased incidence of seizures in epileptic patients
    • Cartilage toxicity and joint swelling in children

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    Description

    This quiz covers the mechanisms of antibiotic action, particularly the inhibition of nucleic acid synthesis and other related processes. It's a useful resource for students of medical pharmacology and microbiology.

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