Metronidazole and Nitrofurantoin Quiz
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Questions and Answers

Which enzyme is inhibited by fluoroquinolones, leading to their antimicrobial activity?

  • DNA polymerase
  • RNA helicase
  • DNA gyrase (correct)
  • RNA polymerase

    • In the context of antimetabolites, what reactive free radicals are formed by the prodrug Metronidazole that are directly toxic to DNA?

  • Nitrogen radicals
  • Nitric oxide
  • Oxygen ions
  • Hydroxyl radicals (correct)

    • What is the first-line use of fluoroquinolones like levofloxacin and moxifloxacin?

  • Osteomyelitis (correct)
  • MRSA infections
  • Urinary tract infections
  • Anaerobic infections

    • What condition poses a higher risk of anemia in patients taking Sulfamethoxazole + Trimethoprim (SMX/TMP)?

    <p>G6PD deficiency</p> Signup and view all the answers

    Which fluoroquinolone is the only active agent against anaerobic infections on its own?

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

    Which type of killing is associated with the statement 'the LONGER the antibiotic concentration stays above MIC, the greater the extent of killing'?

    <p>Time dependent killing</p> Signup and view all the answers

    Which of the following antibiotics is an example of concentration dependent killing according to the text?

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

    What is the mechanism of action of Sulfamethoxazole + Trimethoprim (SMX/TMP)?

    <p>Inhibition of folic acid synthesis</p> Signup and view all the answers

    What distinguishes Empiric Therapy from Targeted Therapy?

    <p>Knowledge of the causative organism</p> Signup and view all the answers

    Which unique toxicity is associated with Sulfamethoxazole + Trimethoprim (SMX/TMP)?

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

    What is the advantage of using Empiric Therapy according to the text?

    <p>Rapid initiation of treatment</p> Signup and view all the answers

    What is a common indication for Sulfamethoxazole + Trimethoprim (SMX/TMP)?

    <p>Urinary tract infections</p> Signup and view all the answers

    What does a Loading Dose (LD) refer to in antimicrobial pharmacokinetics?

    <p>The amount needed to reach therapeutic levels at once</p> Signup and view all the answers

    Which of the following is not a known toxicity associated with SMX/TMP?

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

    What is the mechanism of action of Sulfamethoxazole alone?

    <p>Inhibition of folic acid synthesis</p> Signup and view all the answers

    What is the significance of the Minimum Inhibitory Concentration (MIC) of an antibiotic?

    <p>It inhibits visible bacterial growth</p> Signup and view all the answers

    Which statement accurately describes the Minimum Bacteriostatic Concentration (MBC) of an antibiotic?

    <p>It results in a 1,000-fold reduction in bacterial density</p> Signup and view all the answers

    If the MBC:MIC ratio is 2, how is the antibiotic classified in terms of its effect on the bacteria?

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

    In terms of antibiotic action, what does it mean if an antibiotic is considered bacteriostatic?

    <p>It slows down the growth of bacteria</p> Signup and view all the answers

    What does it mean when it is said that increasing the concentration of a bacteriostatic antibiotic high enough will turn it into bactericidal?

    <p>The antibiotic will start killing bacteria</p> Signup and view all the answers

    How do Sulfamethoxazole and Trimethoprim (SMX/TMP) work synergistically to prevent bacterial DNA synthesis?

    <p>Sulfamethoxazole competes with PABA for DHPS, while Trimethoprim competes with folate for DHFR</p> Signup and view all the answers

    Which enzyme is targeted by Sulfamethoxazole in bacterial DNA synthesis?

    <p>Dihydropteroate synthase (DHPS)</p> Signup and view all the answers

    What type of infections are Sulfamethoxazole + Trimethoprim (SMX/TMP) NOT reliably active against?

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

    Which of the following is an indication for the use of Sulfamethoxazole + Trimethoprim (SMX/TMP)?

    <p>Active against Gram-positive and Gram-negative infections</p> Signup and view all the answers

    How does Trimethoprim work to inhibit bacterial DNA synthesis in combination with Sulfamethoxazole?

    <p>By competing with folate for DHFR</p> Signup and view all the answers

    Which class of antibiotic inhibitors targets key steps in nucleic acid synthesis during the replication cycle?

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

    What is the mechanism of action of Sulfamethoxazole (SMX) in bacterial DNA synthesis?

    <p>Competes with PABA for DHPS</p> Signup and view all the answers

    Which antibiotic combination has no reliable coverage against Pseudomonas infections?

    <p>Trimethoprim + Sulfamethoxazole (TMP+SMX)</p> Signup and view all the answers

    What is the primary target of Trimethoprim (TMP) in bacterial DNA synthesis when combined with Sulfamethoxazole?

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

    What distinguishes Minimum Inhibitory Concentration (MIC) from Minimum Bactericidal Concentration (MBC)?

    <p>MIC indicates the maximum concentration before bacterial growth; MBC indicates the minimum concentration for killing.</p> Signup and view all the answers

    In the context of antibiotics, what does it mean if an antibiotic is considered bacteriostatic?

    <p>It only prevents bacterial growth without killing them.</p> Signup and view all the answers

    Which antibiotic is no longer used first line to treat uncomplicated C. diff infection?

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

    What is the unique toxicity associated with Nitrofurantoin use?

    <p>Pulmonary fibrosis</p> Signup and view all the answers

    What unique toxicity is associated with Mycobacterial Inhibitors?

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

    Which antibiotic is a DNA synthesis inhibitor and can cause discoloration of body fluids?

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

    In terms of antibiotic action, what does it mean if an antibiotic is considered bacteriostatic?

    <p>It prevents bacterial growth without killing them directly</p> Signup and view all the answers

    What is the specific combination drug for latent tuberculosis?

    <p>Rifampin + Isoniazid</p> Signup and view all the answers

    Which antibiotic should be coadministered with vitamin B6 (pyridoxine) to prevent neuropathy?

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

    What is the role of Minimum Inhibitory Concentration (MIC) in determining antibiotic efficacy?

    <p>It shows the lowest concentration of antibiotic that inhibits bacterial growth.</p> Signup and view all the answers

    What distinguishes concentration dependent killing from time dependent killing of antibiotics?

    <p>Concentration dependent killing is associated with higher antibiotic concentrations above MIC, while time dependent killing focuses on longer durations above MIC</p> Signup and view all the answers

    Which antibiotics are examples of concentration dependent killing according to the text?

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

    What is the primary advantage of using targeted therapy over empiric therapy?

    <p>Targeted therapy minimizes the risk of resistance development</p> Signup and view all the answers

    What is the significance of the Minimum Inhibitory Concentration (MIC) in determining antibiotic efficacy?

    <p>MIC indicates the minimum concentration at which an antibiotic inhibits bacterial growth</p> Signup and view all the answers

    Which enzyme is targeted by fluoroquinolones to exert their antimicrobial activity?

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

    What is the primary difference between empiric therapy and targeted therapy?

    <p>Empiric therapy uses broad-spectrum antibiotics, while targeted therapy uses narrow-spectrum antibiotics</p> Signup and view all the answers

    What does the term Loading Dose (LD) refer to in antimicrobial pharmacokinetics?

    <p>The initial high dose used to rapidly achieve therapeutic levels of the drug</p> Signup and view all the answers

    Which statement accurately describes the Minimum Bactericidal Concentration (MBC) of an antibiotic?

    <p>MBC is the maximum concentration at which an antibiotic kills all bacteria in a sample</p> Signup and view all the answers

    What is the significance of the Minimum Bactericidal Concentration (MBC) of an antibiotic?

    <p>It represents an antibiotic that kills bacteria</p> Signup and view all the answers

    What distinguishes bacteriostatic antibiotics from bactericidal antibiotics?

    <p>Bactericidal antibiotics kill bacteria</p> Signup and view all the answers

    Which type of antibiotic action is associated with an MBC:MIC ratio greater than 4?

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

    In terms of antibiotic classification based on MBC:MIC ratio, what does a ratio less than or equal to 4 indicate?

    <p>Bactericidal action</p> Signup and view all the answers

    What happens theoretically when increasing the concentration of a bacteriostatic antibiotic high enough?

    <p>It turns into a bactericidal antibiotic</p> Signup and view all the answers

    Which antibiotic action is associated with an MBC:MIC ratio greater than 4 in antimicrobial testing?

    <p>Inhibiting bacterial growth</p> Signup and view all the answers

    Which antibiotic is a prodrug that forms reactive free radicals directly toxic to bacterial DNA?

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

    In the context of antibiotics, what does the Minimum Inhibitory Concentration (MIC) measure?

    <p>Concentration above which bacterial growth is inhibited</p> Signup and view all the answers

    What is the unique toxicity associated with fluoroquinolones like ciprofloxacin and levofloxacin?

    <p>Tendon rupture</p> Signup and view all the answers

    Which antibiotic is used first-line in osteomyelitis if the bacteria is sensitive to it?

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

    What does the Minimum Bactericidal Concentration (MBC) of an antibiotic represent?

    <p>Concentration below which bacteria are killed</p> Signup and view all the answers

    Which antibiotic is mainly active against Gram-negative infections and is used topically as ear drops for otic infections?

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

    What is the mechanism of action for nitrofurantoin in inhibiting bacterial growth?

    <p>Mixed DNA and ribosomal inhibition</p> Signup and view all the answers

    Which antibiotic forms reactive free radicals that are toxic to DNA, functioning as a mycobacterial inhibitor?

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

    Study Notes

    Bacterial DNA Synthesis Inhibitors

    • Inhibit bacteria by targeting key steps in nucleic acid synthesis during the replication cycle
    • Subdivided into two classes: Antimetabolites (pseudo-analogs) and Direct enzyme inhibitors blocking synthesis of DNA

    Antimetabolites

    • Sulfamethoxazole + Trimethoprim (SMX/TMP)
      • Sulfamethoxazole is a structural analog of para-amino benzoic acid (PABA)
      • Competes with PABA for dihydropteroate synthase (DHPS) to stop DNA synthesis
      • Trimethoprim is a structural analog of folate
      • Competes with folate for dihydrofolate reductase (DHFR) to stop DNA synthesis
      • SMX+TMP work synergistically to prevent bacterial DNA synthesis
    • Active against Gram positive and Gram negative infections, including MRSA infections
    • No reliable pseudomonas coverage
    • First line option for E.coli (e.g. urinary tract infections), pneumocystis pneumonia (PCP), and toxoplasmosis in immunocompromised patients (e.g. AIDS)

    Direct Enzyme Inhibitors

    • Fluoroquinolones (FQ)
      • Inhibit bacterial topoisomerase II (aka DNA gyrase)
      • Mainly active against Gram negative infections
      • Used FIRST LINE in osteomyelitis (only if the bacteria is sensitive)
      • "Respiratory FQ" are levofloxacin and moxifloxacin
      • Ciprofloxacin is an option to treat urinary tract infections
      • Ofloxacin is used topically as ear drops for otic infections
      • Only agent active against MRSA is delafloxacin
      • Only agent active against anaerobic infection on its own is moxifloxacin
    • Metronidazole
      • Prodrug, forms reactive free radicals that are directly toxic to DNA
      • Mainly active against anaerobic infections (below the diaphragm)
      • First line treatment for trichomonas vaginalis infection and bacterial vaginosis (BV)
      • Used in combination with FQ to treat intra-abdominal infections (e.g. fistulas in patients with inflammatory bowel disease)
    • Nitrofurantoin
      • Broad spectrum, active against Gram positive and Gram negative organisms
      • Used primarily in urinary tract infections
      • Unique toxicity: Pulmonary fibrosis

    Mycobacterial Inhibitors

    • Rifapentine+isoniazid is for latent TB
    • Dapsone is for leprosy (in combo with rifampin)
    • All of them cause hepatotoxicity
    • Unique toxicity: DNA synthesis inhibitor, Induction of hepatic enzymes, Discoloration of body fluids

    Mechanisms of Action

    • Isoniazid: Mycolic acid cell wall inhibitor
    • Pyrazinamide: Unknown
    • Ethambutol: Mycolic acid cell wall inhibitor
    • Rifampin/Rifapentine: Rifampin, Isoniazid, Pyrazinamide, and Ethambutol (RIPE) are for active tuberculosis (TB)

    Antibiotic Summary

    • Concentration dependent killing: The HIGHER the antibiotic concentration is above the MIC, the greater the extent of killing
    • Time dependent killing: The LONGER the antibiotic concentration stays above MIC, the greater the extent of killing
    • Bacteriostatic: An antibiotic that slows down the growth of bacteria
    • Bactericidal: An antibiotic that kills bacteria
    • Empiric Tx: Broad spectrum antibiotic used until lab data comes back
    • Targeted Tx: Narrow spectrum antibiotic selected based on known identity and sensitivity of the causative organism

    Basics of Antimicrobial Pharmacokinetics

    • Loading dose (LD): The amount of drug needed to achieve a therapeutic level in the body
    • Minimum Inhibitory Concentration (MIC): The concentration of antibiotic that inhibits visible bacterial growth at 24 hours
    • Minimum Bactericidal Concentration (MBC): The concentration of antibiotic that results in a 1,000-fold reduction in bacterial density at 24 hours

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    Description

    Test your knowledge on key information about Metronidazole and Nitrofurantoin, including their uses, indications, and toxicities. Explore their roles in treating different infections and understand their clinical significance.

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