Lecture 4.1 - Introduction to antibiotics and other antimicrobials
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Questions and Answers

What is the primary mechanism of action of bacteriostatic antibacterial agents?

  • Inhibiting protein synthesis (correct)
  • Interfering with DNA replication
  • Inhibiting cell wall synthesis
  • Stopping cellular metabolism

    • Which of the following is a characteristic of ideal antimicrobial agents?

  • Rapid onset of action
  • Long half-life (correct)
  • Narrow spectrum of activity
  • High toxicity to host cells

    • What is the primary mechanism of resistance to antibiotics in bacterial biofilms?

  • Production of beta-lactamases
  • Formation of a polysaccharide matrix (correct)
  • Altered target site
  • Reduced permeability and increased efflux

    • Which of the following is NOT a mechanism of antimicrobial resistance?

    <p>Increased uptake</p> Signup and view all the answers

    What is the unit of measurement for minimum inhibitory concentration (MIC) in antibiotic sensitivity testing?

    <p>mg/L</p> Signup and view all the answers

    What is the primary reason for considering patient's medical history when selecting an antibiotic?

    <p>To identify potential allergies</p> Signup and view all the answers

    Which of the following antibacterial agents is classified as a broad-spectrum agent?

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

    What is the term for the ability of an antibiotic to selectively target bacterial cells while sparing host cells?

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

    What is the primary goal of empirical therapy in antibiotic treatment?

    <p>To provide broad-spectrum coverage until the organism is identified</p> Signup and view all the answers

    Which of the following antibiotics is NOT effective against anaerobes?

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

    What is the primary advantage of using a beta-lactamase inhibitor combination?

    <p>It allows the beta-lactam antibiotic to continue working despite the presence of beta-lactamase</p> Signup and view all the answers

    Which of the following antibiotics is associated with an increased risk of C. difficile infection?

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

    What is the primary indication for using vancomycin?

    <p>Gram-positive bacterial infections, including MRSA and VRE</p> Signup and view all the answers

    Which of the following antibiotics is not typically used to treat multidrug-resistant Gram-negative infections?

    <p>Amoxicillin + clavulanate</p> Signup and view all the answers

    What is the primary advantage of using teicoplanin over vancomycin?

    <p>It is easier to administer</p> Signup and view all the answers

    Which of the following antibiotics is used to treat acute Gram-positive skin infections?

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

    Which of the following mechanisms of antibiotic resistance is characterized by the production of enzymes that destroy or inactivate the antibiotic?

    <p>Drug inactivating enzymes</p> Signup and view all the answers

    What is the primary consideration when selecting an antibiotic for a patient with a severe infection?

    <p>The severity of the infection</p> Signup and view all the answers

    What is the primary advantage of using combination therapy in antibiotic treatment?

    <p>To increase the spectrum of activity against different types of bacteria</p> Signup and view all the answers

    Which of the following types of antibacterial agents is classified based on its mechanism of action?

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

    Which of the following antibiotics is active against most gram positives but not gram negatives?

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

    What is the unit of measurement used to express the results of antibiotic sensitivity testing using the Etest method?

    <p>mg/L</p> Signup and view all the answers

    What is the primary indication for using piperacillin/tazobactam?

    <p>To treat gram-negative infections, including Pseudomonas species</p> Signup and view all the answers

    Which of the following antibiotics requires therapeutic drug monitoring (TDM)?

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

    Which of the following is a characteristic of an ideal antimicrobial agent?

    <p>Selectively toxic</p> Signup and view all the answers

    What is the primary mechanism of antibiotic resistance in bacterial biofilms?

    <p>Biofilm mode of growth</p> Signup and view all the answers

    What is the primary advantage of using teicoplanin over vancomycin?

    <p>It is easier to administer</p> Signup and view all the answers

    Which of the following types of antibacterial agents is classified based on its spectrum of activity?

    <p>Broad-spectrum</p> Signup and view all the answers

    Which of the following antibiotics is used to treat complicated gram-negative urinary tract infections?

    <p>Meropenem + vaborbactam</p> Signup and view all the answers

    What is the primary goal of disc sensitivity testing?

    <p>To predict the clinical response to antibiotic therapy</p> Signup and view all the answers

    What is the primary mechanism of action of beta-lactam antibiotics?

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

    Which of the following antibiotics is active against most gram negatives, including anaerobes?

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

    Study Notes

    Classification of Antimicrobial Agents

    • Antibacterial, antifungal, antiviral, and antiprotozoal agents
    • Antibacterial agents can be classified by:
      • Mechanism of action (bactericidal or bacteriostatic)
      • Spectrum (broad or narrow)
      • Target site
      • Chemical structure (antibacterial class)

    Ideal Features of Antimicrobial Agents

    • Selectively toxic
    • Few adverse effects
    • Reach site of infection
    • Oral or IV formulation
    • Long half-life (infrequent dosing)
    • No interference with other drugs

    Mechanisms of Resistance

    • Drug inactivating enzymes (e.g. beta-lactamases, aminoglycoside enzymes)
    • Altered target (e.g. resistance to methicillin, macrolides, and trimethoprim)
    • Altered uptake (decreased permeability or increased efflux)
    • Biofilm mode of growth (made of polysaccharides)

    Genetic Mechanisms of Resistance

    • None mentioned

    Measuring Antibiotic Activity

    • Disc sensitivity testing (sensitive, intermediate, or resistant)
    • Antibiotic sensitivity by Etest (minimum inhibitory concentration (MIC) as mg/L)
    • Automated antibiotic sensitivity testing (MIC as mg/L)

    Considerations for Antibiotic Therapy

    • Severity/cause of infection
    • Patient's medical history, other drugs, and allergy to antibiotics
    • Taking samples before start of antibiotic therapy
    • Broad spectrum antibiotics for unidentified causative organisms
    • Route of administration (oral or IV)
    • Dose of antibiotics
    • Longevity of therapy
    • Combination therapy
    • Prophylaxis

    Selection of Antibiotics for Treatment

    • Empirical therapy initially
    • Isolate and identify the organism
    • Determine its sensitivity
    • Treat with an appropriate antibiotic

    Beta-lactams

    • Penicillins:
      • Penicillin (mainly active against streptococci)
      • Amoxicillin (active against streptococci and some gram-negatives)
      • Flucloxacillin (active against staphylococci and streptococci)
      • Beta-lactamase inhibitor combinations (e.g. amoxicillin/clavulanate, piperacillin/tazobactam)
    • Cephalosporins:
      • Broad-spectrum but no anaerobe activity
      • Cetriaxone (good activity in the CSF)
      • Concern over association with C.difficile
      • Ceftazidime + avibactam and ceftlozane + tazobactam (used for multidrug resistant Gram negative infections)
    • Carbapenems:
      • Imipenem, meropenem, and ertapenem (broad spectrum, including anaerobes)
      • Active against most gram negatives
      • Generally safe in penicillin allergy
      • Imipenem + relebactam (used for serious gram negative infections)
      • Meropenem + vaborbactam (used for complicated gram negative UTI)

    Glycopeptides

    • Vancomycin:
      • Active against most gram positive (not gram negative)
      • Some enterococci resistant (VRE)
      • Resistance in staphs rare
      • Not absorbed (oral for C.difficile only)
      • Therapeutic drug monitoring (TDM) required (narrow therapeutic window)
    • Teicoplanin:
      • Similar activity to vancomycin
      • Easier to administer
    • Dalbavancin and telavancin:
      • Used for acute gram positive skin infections
      • Used for MRSA pneumonia

    Tetracyclines

    • Tetracycline and doxycycline:
      • Similar spectrum, both oral only

    Classification of Antimicrobial Agents

    • Antibacterial, antifungal, antiviral, and antiprotozoal agents
    • Antibacterial agents can be classified by:
      • Mechanism of action (bactericidal or bacteriostatic)
      • Spectrum (broad or narrow)
      • Target site
      • Chemical structure (antibacterial class)

    Ideal Features of Antimicrobial Agents

    • Selectively toxic
    • Few adverse effects
    • Reach site of infection
    • Oral or IV formulation
    • Long half-life (infrequent dosing)
    • No interference with other drugs

    Mechanisms of Resistance

    • Drug inactivating enzymes (e.g. beta-lactamases, aminoglycoside enzymes)
    • Altered target (e.g. resistance to methicillin, macrolides, and trimethoprim)
    • Altered uptake (decreased permeability or increased efflux)
    • Biofilm mode of growth (made of polysaccharides)

    Genetic Mechanisms of Resistance

    • None mentioned

    Measuring Antibiotic Activity

    • Disc sensitivity testing (sensitive, intermediate, or resistant)
    • Antibiotic sensitivity by Etest (minimum inhibitory concentration (MIC) as mg/L)
    • Automated antibiotic sensitivity testing (MIC as mg/L)

    Considerations for Antibiotic Therapy

    • Severity/cause of infection
    • Patient's medical history, other drugs, and allergy to antibiotics
    • Taking samples before start of antibiotic therapy
    • Broad spectrum antibiotics for unidentified causative organisms
    • Route of administration (oral or IV)
    • Dose of antibiotics
    • Longevity of therapy
    • Combination therapy
    • Prophylaxis

    Selection of Antibiotics for Treatment

    • Empirical therapy initially
    • Isolate and identify the organism
    • Determine its sensitivity
    • Treat with an appropriate antibiotic

    Beta-lactams

    • Penicillins:
      • Penicillin (mainly active against streptococci)
      • Amoxicillin (active against streptococci and some gram-negatives)
      • Flucloxacillin (active against staphylococci and streptococci)
      • Beta-lactamase inhibitor combinations (e.g. amoxicillin/clavulanate, piperacillin/tazobactam)
    • Cephalosporins:
      • Broad-spectrum but no anaerobe activity
      • Cetriaxone (good activity in the CSF)
      • Concern over association with C.difficile
      • Ceftazidime + avibactam and ceftlozane + tazobactam (used for multidrug resistant Gram negative infections)
    • Carbapenems:
      • Imipenem, meropenem, and ertapenem (broad spectrum, including anaerobes)
      • Active against most gram negatives
      • Generally safe in penicillin allergy
      • Imipenem + relebactam (used for serious gram negative infections)
      • Meropenem + vaborbactam (used for complicated gram negative UTI)

    Glycopeptides

    • Vancomycin:
      • Active against most gram positive (not gram negative)
      • Some enterococci resistant (VRE)
      • Resistance in staphs rare
      • Not absorbed (oral for C.difficile only)
      • Therapeutic drug monitoring (TDM) required (narrow therapeutic window)
    • Teicoplanin:
      • Similar activity to vancomycin
      • Easier to administer
    • Dalbavancin and telavancin:
      • Used for acute gram positive skin infections
      • Used for MRSA pneumonia

    Tetracyclines

    • Tetracycline and doxycycline:
      • Similar spectrum, both oral only

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    Quiz on the classification of antibacterial, antifungal, antiviral, and antiprotozoal agents based on their mechanism of action, spectrum, target site, and chemical structure.

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