Introduction to Drug/Antimicrobial Therapy
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Questions and Answers

What are the four basic steps of gram staining?

Primary stain, secondary stain, decolorization, and counterstaining.

What is the purpose of selective toxicity in drug therapy?

The aim is to eradicate a parasite while minimizing harm to the host organism. This is achieved by exploiting the inherent differences between the pathogen and host.

Which of the following is NOT a characteristic of a gram-positive bacteria cell wall?

  • Multiple peptidoglycan layers
  • Presence of an outer lipid membrane (correct)
  • Thick peptidoglycan layers

    • What is the relationship between the zone of inhibition in a Kirby-Bauer test and the efficacy of a drug?

    <p>A larger zone of inhibition indicates a more effective drug.</p> Signup and view all the answers

    Which of the following accurately describes the relationship between Minimum Bactericidal Concentration (MBC) and Minimum Inhibitory Concentration (MIC)?

    <p>MBC/MIC ≤ 4: Bactericidal</p> Signup and view all the answers

    Herbal supplements always have a positive effect on the immune system.

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

    What is the most common mechanism of antibiotic resistance?

    <p>Inactivation of the antibiotic by bacterial beta-lactamases.</p> Signup and view all the answers

    Which of the following is NOT a common adverse effect of sulfonamides?

    <p>Cardiac arrhythmias</p> Signup and view all the answers

    What is the mechanism of action of quinolones?

    <p>Quinolones inhibit bacterial DNA synthesis by targeting and inhibiting bacterial proteins like topoisomerases II (DNA gyrase) and topoisomerase IV. This prevents the relaxation of positively supercoiled DNA, which is essential for normal replication and transcription.</p> Signup and view all the answers

    Which of the following is a clinical use of fluoroquinolones?

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

    What is the unique structural feature of penicillin?

    <p>The unique four-membered lactam ring.</p> Signup and view all the answers

    Which of the following describes the mechanism of action of penicillins?

    <p>Interference with bacterial cell wall synthesis</p> Signup and view all the answers

    What is the main difference between gram-positive and gram-negative bacteria in terms of their cell wall structure?

    <p>Gram-positive bacteria have a thick layer of peptidoglycan, while gram-negative bacteria have a thinner layer of peptidoglycan and an additional outer membrane.</p> Signup and view all the answers

    Which of the following mechanisms is NOT a way bacteria develop resistance to penicillin?

    <p>Enhanced permeability of the bacterial cell wall</p> Signup and view all the answers

    Tetracyclines are typically considered bacteriostatic, meaning they inhibit bacterial growth but do not kill them.

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

    Describe the mechanism of action of tetracyclines.

    <p>Tetracyclines enter bacteria through passive diffusion or active transport and bind to the 30S subunit of the bacterial ribosome, blocking the attachment of aminoacyl-tRNA to the acceptor site.</p> Signup and view all the answers

    What is the primary route of elimination of tetracyclines?

    <p>Both renal and biliary excretion</p> Signup and view all the answers

    What are the common adverse effects of tetracyclines?

    <p>Common adverse effects of tetracyclines include gastrointestinal upset, hypersensitivity reactions, discoloration of teeth, and photosensitivity.</p> Signup and view all the answers

    Aminoglycosides are primarily bacteriostatic, meaning they inhibit bacterial growth but do not kill them.

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

    What are the three main mechanisms of action of aminoglycosides?

    <p>Aminoglycosides interfere with protein synthesis in bacteria through three mechanisms.</p> Signup and view all the answers

    Which of the following is NOT a typical clinical use for aminoglycosides?

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

    What is the mechanism of action of vancomycin?

    <p>Vancomycin inhibits bacterial cell wall synthesis by binding to the D-Ala-D-Ala terminus of peptidoglycan pentapeptide.</p> Signup and view all the answers

    Macrolides are typically considered bacteriostatic, meaning they inhibit bacterial growth but do not necessarily kill them.

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

    What are the common adverse effects of macrolides?

    <p>Common adverse effects of macrolides include gastrointestinal upset, hypersensitivity reactions, and drug interactions.</p> Signup and view all the answers

    What is the primary clinical use of azithromycin?

    <p>Treatment of sexually transmitted infections like chlamydia</p> Signup and view all the answers

    What is the mechanism of action of fidaxomicin?

    <p>Fidaxomicin inhibits bacterial RNA polymerase, blocking bacterial protein synthesis.</p> Signup and view all the answers

    Chloramphenicol is a broad-spectrum antibiotic with a wide range of activity against various bacteria, viruses, and fungi.

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

    What is the primary mechanism of resistance to chloramphenicol?

    <p>The primary mechanism of resistance to chloramphenicol is the production of chloramphenicol acetyltransferase.</p> Signup and view all the answers

    Which of the following is a common adverse effect of chloramphenicol?

    <p>Bone marrow suppression</p> Signup and view all the answers

    Metronidazole is particularly effective against anaerobic bacteria.

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

    What is the main clinical use of mupirocin?

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

    What is the mechanism of action of nitrofurantoin?

    <p>Nitrofurantoin is bactericidal against many gram-positive and gram-negative bacteria.</p> Signup and view all the answers

    What are the main clinical uses of chlorohexidine?

    <p>Chlorohexidine, a topical antiseptic, is primarily used for the treatment of gingivitis.</p> Signup and view all the answers

    What is the main clinical relevance of antiprotozoal drugs?

    <p>Antiprotozoal drugs are particularly relevant for treating parasitic infections, such as malaria.</p> Signup and view all the answers

    What is the most effective drug for treating non-resistant forms of Plasmodium?

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

    What is the mechanism of action of chloroquine?

    <p>Chloroquine interferes with the heme detoxification process in the parasite.</p> Signup and view all the answers

    What is the main clinical use of mefloquine?

    <p>Prophylaxis against malaria</p> Signup and view all the answers

    Primaquine has been found to be effective against both blood stages and liver stages of Plasmodium vivax and Plasmodium ovale.

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

    What are the main clinical uses of artemisinin?

    <p>Artemisinin and its derivatives are important for treating severe malaria infections.</p> Signup and view all the answers

    There are currently no vaccines available in the United States for malaria.

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

    What is the main reason for the importance of antimycobacterial drugs?

    <p>Antimycobacterial drugs target Mycobacterium tuberculosis.</p> Signup and view all the answers

    Which of the following is NOT a first-line drug used in the initial treatment of tuberculosis?

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

    What is the mechanism of action of isoniazid?

    <p>Isoniazid, a prodrug, needs to be activated by the bacterial enzyme, catalase-peroxidase (KatG).</p> Signup and view all the answers

    Which of the following describes a common side effect of isoniazid?

    <p>Peripheral neuropathy</p> Signup and view all the answers

    What is the mechanism of action of rifampin?

    <p>Rifampin binds to the beta subunit of bacterial RNA polymerase, preventing the transcription of bacterial DNA.</p> Signup and view all the answers

    Ethambutol is primarily effective against the blood stage of Mycobacterium tuberculosis.

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

    What are the common side effects of ethambutol?

    <p>The most common side effect of ethambutol is retrobulbar neuritis.</p> Signup and view all the answers

    What is the mechanism of action of pyrazinamide?

    <p>The precise mechanism of action for pyrazinamide remains unknown.</p> Signup and view all the answers

    Which of the following is the primary mechanism of action for capreomycin?

    <p>Inhibition of bacterial protein synthesis</p> Signup and view all the answers

    Cycloserine is primarily effective against Mycobacterium tuberculosis.

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

    What is the mechanism of action of aminosalicylic acid?

    <p>Aminosalicylic acid is a folic acid synthesis antagonist.</p> Signup and view all the answers

    Rifabutin, a derivative of rifampin, is less potent an inducer of CYP450 enzymes.

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

    What is the primary use of amikacin?

    <p>Treating multidrug-resistant tuberculosis infections</p> Signup and view all the answers

    What are the common side effects of linezolid?

    <p>The common side effects of linezolid include bone marrow suppression and reversible neuropathy.</p> Signup and view all the answers

    Rifapentine is generally a good alternative to rifampin for treating patients with HIV who are receiving antiretroviral therapy (ART).

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

    What is the primary clinical use of bedaquiline?

    <p>Treating multidrug-resistant tuberculosis infections</p> Signup and view all the answers

    Fluoroquinolones are generally used as a primary treatment option for treating tuberculosis.

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

    Study Notes

    Introduction to Drug/Antimicrobial Therapy

    • Drugs used to eradicate a parasite with minimal harm to the host organism
    • "Parasite" includes viruses, bacteria, fungi, and protozoa
    • Analogy of warfare—living enemy adapting faster than human targets

    Selective Toxicity

    • Specificity: Drug needs to be more toxic to the parasite than the host.
    • Biochemical/physiological differences (e.g., penicillin—host vs. parasite)
    • Restricted distribution: e.g., blood-tissue barriers (BBB)
    • Drug effectiveness: Related to differences between pathogen and host.

    Kirby-Bauer Disc Diffusion Test

    • Agar plate containing colonies of bacteria
    • Bacteria in broth
    • Streak bacteria onto a new agar plate
    • Add drug-impregnated discs to be tested
    • Incubate 18-24 hours at 37°C
    • Measure zones of inhibition
    • Bigger the zone, greater the efficacy

    Minimum Inhibitory Concentration (MIC)

    • Dilution test for antimicrobial drug concentrations (µg/mL)
    • MIC: Minimum concentration of drug to inhibit visible growth
    • MBC/MIC ≤ 4: Bactericidal
    • MBC/MIC > 4: Bacteriostatic
    • Epsilometer (E) test: similar method with a different device

    Gram Staining

    • Differentiates Gram-positive and Gram-negative bacteria
    • Gram-positive: purple
    • Gram-negative: pink

    Role of Immune Response

    • Affected by immune response: effects drug's ability to fight infection
    • Absence of immune response: impaired immune system (e.g., AIDS).
    • Use of immunosuppressant drugs (e.g., cyclosporins, corticosteroids)
    • Increased pathogen numbers - greater challenge for antimicrobial agents
    • Altered drug distribution due to increased inflammation

    Herbal Supplements

    • Some herbal supplements (e.g., St. John's Wort) may induce drug transporters (e.g., P-glycoprotein) and drug metabolic enzymes (e.g., CYP3A4).
    • These can majorly effect drug metabolism.

    Drug Resistance

    • Mechanisms of resistance:

      • Increased rate of drug inactivation:
      • Altered amount or decreased affinity of target enzyme/receptor
      • Increased drug efflux and metabolism
      • Decreased drug uptake

    • Resistance: mutations or conjugation

    • Excessive use of antibiotics causes bacteria to become resistant.

    Therapeutic Index (TI)

    • TI = LD50 / ED50
    • LD50: Lethal dose of a drug for 50% of the animals
    • ED50: Effective dose for 50% of the population
    • Wide therapeutic index is preferred

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    Description

    Explore the principles of drug therapy designed to eliminate parasites while minimizing harm to the host organism. Understand selective toxicity, the Kirby-Bauer disc diffusion test, and the significance of the minimum inhibitory concentration in assessing drug efficacy against pathogens. This quiz will deepen your knowledge of antimicrobial agents and their mechanisms.

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