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Questions and Answers
What is one major challenge in treating viral infections?
What is one major challenge in treating viral infections?
Which of the following antifungal agents is used for systemic infections?
Which of the following antifungal agents is used for systemic infections?
What is a common feature of helminth treatment agents?
What is a common feature of helminth treatment agents?
Which of the following is NOT a mechanism of antiviral agents?
Which of the following is NOT a mechanism of antiviral agents?
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What is the role of metronidazole?
What is the role of metronidazole?
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Which agent is derived from the bark of cinchona trees?
Which agent is derived from the bark of cinchona trees?
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Which of the following synthetic agents is used for treating Plasmodium infections?
Which of the following synthetic agents is used for treating Plasmodium infections?
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What type of infections do echinocandins primarily target?
What type of infections do echinocandins primarily target?
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What is the primary action of an antimicrobial agent?
What is the primary action of an antimicrobial agent?
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Which term best describes a drug that prevents the growth of microorganisms?
Which term best describes a drug that prevents the growth of microorganisms?
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What characteristic of antimicrobial drugs determines their effectiveness?
What characteristic of antimicrobial drugs determines their effectiveness?
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Which of the following is NOT a process involved in pharmacokinetics?
Which of the following is NOT a process involved in pharmacokinetics?
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How do water-soluble drugs behave in the body?
How do water-soluble drugs behave in the body?
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What is the significance of the blood-brain barrier in drug distribution?
What is the significance of the blood-brain barrier in drug distribution?
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Which method involves administering drugs via the digestive route?
Which method involves administering drugs via the digestive route?
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What must happen for a drug to be effective after administration?
What must happen for a drug to be effective after administration?
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What is the primary organ responsible for drug metabolism?
What is the primary organ responsible for drug metabolism?
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Which of the following statements about drug metabolites is true?
Which of the following statements about drug metabolites is true?
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What is the process by which drugs are cleared from the body primarily through the kidneys?
What is the process by which drugs are cleared from the body primarily through the kidneys?
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Which type of antimicrobial action kills microbes and can potentially lead to superinfection?
Which type of antimicrobial action kills microbes and can potentially lead to superinfection?
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What is selective toxicity in the context of antimicrobial drugs?
What is selective toxicity in the context of antimicrobial drugs?
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Why are most antimicrobial drugs designed to target prokaryotic cells?
Why are most antimicrobial drugs designed to target prokaryotic cells?
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What defines broad-spectrum antimicrobial agents?
What defines broad-spectrum antimicrobial agents?
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Which of the following statements about tubular reabsorption in the kidneys is correct?
Which of the following statements about tubular reabsorption in the kidneys is correct?
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What is the primary action of β-Lactam antibiotics in bacterial cells?
What is the primary action of β-Lactam antibiotics in bacterial cells?
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Which type of bacteria is primarily affected by penicillin's mechanism of action?
Which type of bacteria is primarily affected by penicillin's mechanism of action?
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What makes protein biosynthesis a selective target for antibacterial drugs?
What makes protein biosynthesis a selective target for antibacterial drugs?
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Which of the following antibiotics target the bacterial membrane?
Which of the following antibiotics target the bacterial membrane?
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What is a consequence of using polymyxins as antibacterial drugs?
What is a consequence of using polymyxins as antibacterial drugs?
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What is the role of penicillin-binding proteins (PBPs) in bacterial cells?
What is the role of penicillin-binding proteins (PBPs) in bacterial cells?
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Why are polymyxins considered to have non-selective toxicity?
Why are polymyxins considered to have non-selective toxicity?
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What distinguishes eukaryotic ribosomes from bacterial ribosomes?
What distinguishes eukaryotic ribosomes from bacterial ribosomes?
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What is the main mechanism by which quinolone antibiotics lead to cell death?
What is the main mechanism by which quinolone antibiotics lead to cell death?
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Which of the following compounds are targeted by sulfonamides and trimethoprim?
Which of the following compounds are targeted by sulfonamides and trimethoprim?
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Which factor is NOT a key cause of antimicrobial resistance?
Which factor is NOT a key cause of antimicrobial resistance?
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How does resistance to antimicrobial drugs often manifest?
How does resistance to antimicrobial drugs often manifest?
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What term describes bacteria that have developed resistance to multiple antibiotics?
What term describes bacteria that have developed resistance to multiple antibiotics?
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What consequence does competitive inhibition of bacterial metabolic enzymes lead to?
What consequence does competitive inhibition of bacterial metabolic enzymes lead to?
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What is a common measurable outcome of antimicrobial effectiveness testing?
What is a common measurable outcome of antimicrobial effectiveness testing?
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Which of the following is NOT a method by which bacteria can acquire drug resistance?
Which of the following is NOT a method by which bacteria can acquire drug resistance?
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Study Notes
Antimicrobial Drugs
- Antimicrobial agents kill or prevent the growth of microorganisms.
- These agents can be classified according to the type of microorganism they target: antibiotics (bacteria), antifungals (fungi), antivirals (viruses), and antiparasitics (parasites)
- Antimicrobial drugs work by disrupting metabolic processes or structural components of the targeted microorganism.
- Microbicidal agents kill microbes; microbiostatic agents inhibit their growth.
Learning Outcomes
- Understand and compare different mechanisms of antimicrobial action.
- Define characteristics of antimicrobial drugs.
- Explain antimicrobial resistance mechanisms.
- Name specific antimicrobial drugs and their mechanisms of action.
What is an Antimicrobial?
- Antimicrobials are medicines that fight infections caused by microorganisms in humans, animals, and plants.
- Different kinds of antimicrobials exist like Antibiotics (e.g. against bacteria), Antifungals, Antivirals or Antiparasitics.
- They can be microbiocidal (killing microbes) or microbiostatic (preventing growth).
- Antimicrobials are often targeted at specific types of microorganisms
Principles of Drug Action
- Drugs alter physiological activities.
- They must reach their intended target in an appropriate concentration.
- Pharmacokinetics is involved in this process. It is the study of how the body handles a drug.
- Aspects of pharmacokinetics include: drug administration, absorption, distribution, biotransformation, and clearance.
Drug Administration
- Drugs can be administered orally (digestive route) or parenterally (any other route)
- Absorption is the rate at which the drug leaves the site of administration and is taken into the body, and how efficiently it reaches the target site.
- Drugs have to be dissolved in body fluids to be absorbed.
- Drugs have to pass through biological barriers to reach their intended target areas in the body.
Drug Distribution
- Transferring drugs across biological membranes into body compartments.
- Drug distribution depends on chemical properties (e.g., solubility), blood flow, molecular size, and more.
- The blood-brain barrier can hinder drug distribution.
- The placenta acts as a pathway for drugs to cross.
Biotransformation
- The liver plays the primary role in drug metabolism.
- Other organs (lungs, kidneys, adrenal glands) are also involved.
- Drug metabolites must be water-soluble for excretion by the kidneys.
Clearance
- Mainly involves the kidneys (glomerular filtration, tubular reabsorption, tubular secretion).
- Some drugs are metabolized in the liver and excreted via bile.
Mechanisms of Antimicrobial Action
- Goal: disrupt the microorganism's metabolism or structure to prevent survival or reproduction.
- Microbicidal: Kills microbes; can potentially kill normal flora, leading to potential superinfection.
- Bacteriolytic: Kills/lyses the cells of the target microorganism.
- Microbiostatic: Inhibit growth, reversible.
Spectrum of Action
- Broad spectrum: effective against a wide range of microorganisms.
- Narrow spectrum: effective against a limited variety of organisms (avoiding damage to normal flora).
- Medium spectrum: effective against some gram-positive and gram-negative bacteria (not all).
Antimicrobial Agents
- Many different types of microorganisms exist (bacteria, eukaryotes, viruses, parasites).
- One drug does not effectively combat all microbes, as their structures and functions differ.
- Different drugs target different microbes.
Selective Toxicity
- Antimicrobial drugs should selectively affect harmful microbes while minimizing harm to host cells.
- Prokaryotic (bacteria) cell components are different from eukaryotic (animal) components, allowing for selective targets within the bacteria.
Mode of Action
- Many antimicrobials block critical metabolic pathways in the target organism, targeting specific processes such as cell wall, DNA/RNA synthesis, protein synthesis, plasma membranes, etc)
Inhibition of Cell Wall Biosynthesis
- Beta-lactam antibiotics (e.g., penicillin) interfere with cell wall formation in bacteria. (by binding to penicillin-binding proteins).
- Bacteria require peptidoglycans for the cell wall.
- Resistance to antibiotics can occur when bacteria have mutated and the antibiotic no longer works on them.
Inhibition of Protein Synthesis
- Drugs inhibiting protein synthesis in bacteria affect the ribosomes and block the process.
- Different classes of antibacterials target these steps to prevent protein synthesis in bacteria.
Disruption of Plasma Membrane
- Polymyxins disrupt bacterial membranes.
- These are not selective as they also damage eukaryotic cells.
Inhibition of Nucleic Acid Synthesis
- Quinolones block DNA supercoiling by binding to topoisomerases.
- Inhibiting DNA replication/synthesis in bacteria.
Inhibition of Metabolic Pathways
- Some drugs work as antimetabolites, stopping critical metabolic pathways (e.g., inhibiting folic acid synthesis).
- They are competitive inhibitors, targeting specific enzymes.
Resistance to Antimicrobial Drugs
- Overprescription, incomplete treatment courses, poor infection control, and misuse in agriculture are some factors promoting microbial resistance to drugs.
- Resistant microbes can survive, and their resistant genes can transfer to other microbes.
- Limited discovery of new antimicrobials.
- Mechanisms of resistance in microbes can include changes in membrane permeability, changes in the mechanism of action in target site, changes in metabolic pathways, and new/efficient enzymes developed in resistance.
Antimicrobial Susceptibility Tests (AST)
- Methods like Kirby-Bauer disk diffusion are used to determine the susceptibility of microbes to different antimicrobials, providing important information for treatment considerations.
Acquisition of Drug Resistance
- Improper use of prescribed antimicrobials promotes the development of resistant microbes.
- Microbes can develop various mechanisms to avoid the effects of the drug treatment.
- Misuse and overprescription of antimicrobials has led to drug-resistant bacteria.
Multiple Resistances
- Antibiotic resistance is a global problem—especially prevalent in healthcare facilities.
- Bacteria that are resistant to multiple antibiotics are called superbugs—they are a major threat to public health.
Preventing Drug Resistance
- Strategies for preventing drug resistance include careful prescriptions, proper duration of treatment, and addressing resistance issues in agriculture and healthcare environments.
- Education plays an important role in reducing antibiotic misuse and promoting appropriate antibiotic stewardship across populations.
Antiviral Agents
- Most viruses lack a cure and have limited effectiveness.
- Resistance to antivirals is also a concern.
- Targeting points in the viral life cycle (penetration, transcription/translation, maturation) often involves preventing the virus from reproducing and spreading.
Antifungal Agents
- Antifungal agents are used to treat fungal infections.
- They often have more side effects on eukaryotic cells than prokaryotic cells, and this can lead to complications.
- Some antifungals target fungal cell membrane functions or nucleic acid synthesis; some examples include macrolide polyene, synthetic azoles, and flucytosine.
Antiprotozoal Agents
- These agents combat protozoan infections.
- Examples include chloroquine, primaquine, metronidazole, pyrimethamine, and quinine.
- These agents are used to treat infections like malaria, giardiasis, and trichomoniasis.
Antihelminthic Agents
- Agents targeting helminths (eukaryotic parasite worms).
- They are designed to inhibit helminthic metabolism or movement.
- Agents including niclosamide, mebendazole, piperazine, and ivermectin are used to treat helminthic infections.
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Description
This quiz covers the essentials of antimicrobial drugs, including their classification and mechanisms of action. You will explore the differences between antibiotics, antifungals, antivirals, and antiparasitics, as well as the concept of antimicrobial resistance. Test your knowledge on specific drugs and their effectiveness against various microorganisms.
