Microbial Resistance and Drug Susceptibility Quiz
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Questions and Answers

What should the peak serum concentration of a drug typically be in relation to the MIC for effective drug susceptibility?

  • Less than the MIC
  • 1 to 3 times greater
  • 4 to 10 times greater (correct)
  • 10 to 15 times greater

    • Which mechanism is NOT a primary mechanism of microbial resistance?

  • Increased absorption of the drug (correct)
  • Decreased accumulation of the drug by the microbe
  • Modification of drug target sites
  • Inactivation of the drug by microbial enzymes

    • Acquired drug resistance can arise from spontaneous mutation at what approximate rate?

  • 1 in 10^12 (correct)
  • 1 in 100,000
  • 1 in 10
  • 1 in 1,000

    • Which method is commonly associated with transferable drug resistance?

    <p>Bacterial transformation</p> Signup and view all the answers

    What are the proteins produced from resistance factors (R factors) responsible for?

    <p>Conferring drug resistance</p> Signup and view all the answers

    Bacterial conjugation primarily involves what kind of genetic material?

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

    Which process allows for the transfer of bacterial DNA by a bacteriophage?

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

    What happens during the selection of resistant mutants in a culture?

    <p>Resistant mutants become more prevalent</p> Signup and view all the answers

    What does the broth dilution test primarily measure?

    <p>Minimal inhibitory concentration (MIC)</p> Signup and view all the answers

    In the disk diffusion method, how is antibiotic effectiveness evaluated?

    <p>By measuring the zone of inhibition</p> Signup and view all the answers

    What does the E-test method utilize to determine the MIC?

    <p>A gradient of antibiotic concentrations on a strip</p> Signup and view all the answers

    How are organisms classified after testing in the methods discussed?

    <p>As susceptible, intermediate sensitivity, or resistant</p> Signup and view all the answers

    What role does the peak serum concentration of a drug play in interpreting MIC results?

    <p>It affects the classification of organisms as susceptible or resistant.</p> Signup and view all the answers

    Which of the following methods involves the measurement of an inhibition zone around an antibiotic disk?

    <p>Disk diffusion method</p> Signup and view all the answers

    In the broth dilution test, what does visible growth indicate?

    <p>The antibiotic concentration was ineffective</p> Signup and view all the answers

    What is a limitation of the disk diffusion method?

    <p>It does not provide quantitative results.</p> Signup and view all the answers

    What is one mechanism of microbial resistance that involves altering the drug's target area?

    <p>Reduced affinity of the target macromolecule for the drug</p> Signup and view all the answers

    Which of the following is a consequence of decreased drug accumulation in microbes?

    <p>Decreased uptake due to altered porins in gram-negative bacteria</p> Signup and view all the answers

    Which of the following host factors can influence the selection of antimicrobial drugs?

    <p>The patient's immune status</p> Signup and view all the answers

    What specific type of enzyme is responsible for the inactivation of penicillins and other β-lactam antibiotics?

    <p>β-lactamase enzyme</p> Signup and view all the answers

    Which antibiotics have reduced affinity due to changes in ribosomal bonding sites?

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

    Which of the following represents a common empiric selection basis for antimicrobial activity?

    <p>Knowledge of common organisms causing infections</p> Signup and view all the answers

    Decreased uptake and increased efflux of which drug class is seen in certain microbial resistance mechanisms?

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

    What host factor could significantly impact the selection of antimicrobial therapy in a patient?

    <p>Presence of indwelling catheters</p> Signup and view all the answers

    What principle underpins the effectiveness of chemotherapy?

    <p>Selective toxicity</p> Signup and view all the answers

    Which of the following is NOT a class of chemotherapeutic drugs?

    <p>Antidiabetic agents</p> Signup and view all the answers

    What was one early historical use of antibiotics?

    <p>Moldy bean curd for skin infections</p> Signup and view all the answers

    Who is credited with the discovery of penicillin?

    <p>Alexander Fleming</p> Signup and view all the answers

    What mechanism is primarily involved in the harm caused by chemotherapeutic drugs?

    <p>Selective inhibition of vital functions in pathogens</p> Signup and view all the answers

    What was a significant impact of the discovery of penicillin?

    <p>Sparking the development of other antibiotics</p> Signup and view all the answers

    Which historical figure used mercury compounds for treating syphilis?

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

    Which of the following best describes 'antibiosis'?

    <p>The interaction between one bacterium inhibiting another</p> Signup and view all the answers

    What is the definition of a synergistic effect in the context of drug interactions?

    <p>The combined effect is greater than the sum of the independent effects.</p> Signup and view all the answers

    Which drugs can have additive or synergistic effects against gram-negative bacilli?

    <p>Penicillins and aminoglycosides</p> Signup and view all the answers

    What is the result of combining a bactericidal drug with a bacteriostatic drug?

    <p>Reduced effectiveness of the bactericidal drug</p> Signup and view all the answers

    What is a consequence of combination therapy in treating tuberculosis?

    <p>Delay in the emergence of resistant organisms</p> Signup and view all the answers

    What do drugs sulfamethoxazole and trimethoprim do together?

    <p>They inhibit separate steps in folate synthesis.</p> Signup and view all the answers

    Which statement about the mutation rate of Mycobacterium tuberculosis is true?

    <p>It is unlikely that a resistant mutant will emerge during combination therapy.</p> Signup and view all the answers

    What characterizes an indifferent interaction of two antimicrobial drugs?

    <p>The combined effect is similar to the effect of the most effective drug alone.</p> Signup and view all the answers

    What is an example of a situation where drugs exhibit mutual antagonism?

    <p>Drugs canceling each other’s effects when combined</p> Signup and view all the answers

    Why can aminoglycosides be administered intrathecally for meningitis treatment?

    <p>They achieve adequate concentrations in cerebrospinal fluid.</p> Signup and view all the answers

    What is the reason patients with osteomyelitis are treated with antibiotics for several weeks?

    <p>Low drug concentrations are present in bone.</p> Signup and view all the answers

    Which drug class is most effective for urinary tract infections due to renal excretion?

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

    Which antibiotics are generally safer with a low incidence of organ system toxicity?

    <p>Macrolides and β-lactams</p> Signup and view all the answers

    When is combination drug therapy commonly used?

    <p>For suspected mixed infections.</p> Signup and view all the answers

    What describes an antagonistic interaction between two drugs?

    <p>The combined effect is less than the effect of either drug alone.</p> Signup and view all the answers

    Which drugs are more likely to accumulate in patients with renal dysfunction?

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

    Why might prostatic fluid limit the effectiveness of certain antibiotics?

    <p>Due to the low pH restricting weak bases.</p> Signup and view all the answers

    Study Notes

    Introduction to Chemotherapy

    • Chemotherapy involves using drugs to eliminate pathogenic organisms or cancerous cells.
    • The principle behind chemotherapy is selective toxicity, targeting a crucial function in invading organisms (or cancer cells) that differs from the host's.

    Objectives

    • Understand the mechanisms of selective toxicity in chemotherapeutic drugs.
    • Describe the modes of action of various chemotherapeutic drugs.
    • Detail the side effects associated with these drugs, including resistance mechanisms.

    Overview

    • Chemotherapy aims to eradicate pathogenic organisms or cancerous cells, treating infectious illnesses and cancer.
    • Selective toxicity is essential for chemotherapy; drugs must inhibit a critical function specific to the disease-causing agent without harming the host.

    The Chemotherapeutic Drugs

    • Antimicrobial drugs (antibacterial, antifungal, and antiviral agents).
    • Antiparasitic drugs.
    • Antineoplastic and immunopharmacology drugs.

    History

    • Early use of antibiotics involved treating skin infections.
    • Louis Pasteur and Paul Vuillemin identified the concept of antibiosis, where one organism inhibits another.
    • Alexander Fleming discovered penicillin while observing a bacterial culture inhibited by a Penicillium mold.

    Synthetic Drugs

    • Historical use of mercury compounds for syphilis treatment.
    • Paul Ehrlich's work on arsphenamine (Salvarsan) initiated chemotherapy.
    • Sulfonamides (derived from Prontosil) were the first effective systemic antibacterial agents.

    Part One: Antimicrobial Drugs

    • Antibiotics categorized as antibacterial agents, antifungal agents, and antiviral agents
    • Antiparasitic drugs in additional sections
    • Antineoplastics and immunopharmacology drugs also covered.

    Classification of Antimicrobial Drugs

    • Cell wall synthesis inhibitors.
    • Protein synthesis inhibitors.
    • Metabolic and nucleic acid inhibitors.
    • Cell membrane inhibitors.

    Antimicrobial Activity of Chemotherapeutic Drugs

    • Bactericidal or bacteriostatic effects.
    • Spectrum of action against pathogens.
    • Concentration and time dependencies affecting effectiveness.

    Effect: Bactericidal or Bacteriostatic.

    • Bactericidal drugs kill pathogens rapidly.
    • Bacteriostatic drugs inhibit pathogen growth but do not kill them.
    • This principle also applies to antifungal drugs.

    In vitro effects of bactericidal and bacteriostatic drugs.

    Bactericidal or Bacteriostatic Drugs

    • Bactericidal drugs work by disrupting essential microbial functions.
    • Bacteriostatic drugs inhibit essential metabolic reactions.

    Bactericidal or Bacteriostatic Drugs

    • Reversible and irreversible protein synthesis inhibitors.
    • Some antibiotics can be either bactericidal or bacteriostatic depending on concentration and pathogen.

    Antimicrobial Spectrum

    • Narrow-spectrum drugs are used against only specific bacteria.
    • Broad-spectrum drugs affect a wider range of bacteria.

    Concentration- and Time-Dependent Effects

    • Minimal inhibitory concentration (MIC) determines bacterial susceptibility.
    • Concentration-dependent killing rate (CDKR) measures rate of death of pathogens.
    • Post-antibiotic effect (PAE) considers persistence of drug's effectiveness after drug removal.

    Some aminoglycosides and some fluoroquinolones.

    • Some aminoglycosides exhibit CDKR against Gram-negative bacteria.
    • Penicillins and other β-lactam antibiotics generally do not exhibit CDKR.

    Bacterial Resistance

    • Innate (pre-existing) vs acquired drug resistance
    • Innate resistance may arise from genetic structure
    • Spontaneous mutations, plasmids (transferable resistance), and transformation / transduction can also cause resistance.

    Primary Mechanisms of Microbial Resistance

    • Drug inactivation by enzymes produced by the microbe.
    • Reduced accumulation of drugs due to impaired uptake or increased efflux.
    • Reduced affinity of the drug target for its macromolecule.

    Mechanism of Microbial Resistance

    • Examples detailed for inactivation, accumulation, affinity reduction

    Some transport proteins.

    • Some microbial resistance arises from transport mechanisms similar to the P-glycoprotein in humans which removes drugs from intracellular compartments (like cancer cells).

    Host Factors

    • Pregnancy, allergies, immune status, kidney and liver function, and presence of indwelling medical devices must be considered.

    Antimicrobial Activity

    • Testing for microbial susceptibility/resistance using broth dilution, disk diffusion (Kirby-Bauer), and E-test methods
    • Essential to diagnose and treat infections correctly.

    The Selection of Antimicrobial Drugs

    • Factors to consider include the causative organism, patient's situation, and other characteristics of the infection / organism

    Prophylactic Therapy

    • Preventive measures such as sterilization of equipment, disinfection, and antibiotic administration can help prevent infections.

    Prevention of Infection During Surgical Procedures

    • Examples of infections and preferred drugs for prevention
    • Pathogens involved

    Prevention of Disease Transmission

    • Infections and their preferred drugs for prevention
    • Example: Prevention of herpes simplex, HIV, or influenza

    Summary of Important Points

    • Overview of antibiotics and antimicrobial actions.
    • Mechanisms of bacterial action
    • Determining sensitivity
    • Resistance mechanisms

    Acquired Microbial Resistance.

    • Resistance can arise from mutations and transfer of genes (R factors) through conjugation, transformation, or transduction.
    • Mechanisms include drug inactivation, reduced uptake, or altered targets.
    • Key factors for selecting drugs, such as considering patient characteristics, the pathogen, type of infection, and drug pharmacokinetics.

    Combination Drug Therapy

    • Combination therapy can help address various forms of infection and limit development of drug resistance through synergy.
    • Different outcomes for treatment depending on whether pathogens are mixed or not.

    Relationship between two drugs and their combined effect

    • Antagonistic
    • Additive
    • Synergistic
    • Indifferent

    Bactericidal drugs

    • Effective against rapidly dividing bacteria
    • Reduced effect if bacterial growth slowed by bacteriostatic drugs

    If two bactericidal drugs that target different microbial functions are given in combination

    • Effects can be additive or synergistic.

    Combination therapy

    • May help prevent resistance in cases such as tuberculosis.
    • Synergistic interactions help limit bacterial growth.

    Prophylactic therapy

    • Preventing infections through measures such as instrument sterilization and preventative antibiotics
    • Key factors for selection are based on risks such as the type of procedure, organism, and patient factors.

    Adverse Effects Profile.

    • Potential drug risks must be weighed against benefits especially when dealing with minor infections.
    • Fluoroquinolones are reasonably safe compared to aminoglycosides.

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    Related Documents

    Introduction to Chemotherapy Pt1 Nov 2024 Notes PDF

    Description

    Test your knowledge on microbial resistance mechanisms and their relation to drug susceptibility. This quiz covers key concepts like peak serum concentration, susceptibility testing methods, and genetic factors involved in resistance. Perfect for students studying microbiology or pharmacology.

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