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Questions and Answers
A new antimicrobial drug selectively targets peptidoglycan synthesis. Which type of microorganism is MOST likely to be affected by this drug?
A new antimicrobial drug selectively targets peptidoglycan synthesis. Which type of microorganism is MOST likely to be affected by this drug?
- Bacteria (correct)
- Parasites
- Fungi
- Viruses
Which of the following BEST describes the difference between bactericidal and bacteriostatic agents?
Which of the following BEST describes the difference between bactericidal and bacteriostatic agents?
- Bactericidal agents kill bacteria, while bacteriostatic agents inhibit bacterial growth. (correct)
- Bactericidal agents inhibit bacterial growth, while bacteriostatic agents kill bacteria.
- Bactericidal agents target viruses, while bacteriostatic agents target bacteria.
- Bactericidal agents are natural, while bacteriostatic agents are synthetic.
An antimicrobial drug is described as having 'selective toxicity'. What does this term imply?
An antimicrobial drug is described as having 'selective toxicity'. What does this term imply?
- The drug targets the pathogen without significantly harming the host cells. (correct)
- The drug is only effective against viruses.
- The drug is effective against a wide range of pathogens and host cells.
- The drug is highly toxic to both the pathogen and the host cells.
Penicillinase producing bacteria exhibit resistance to penicillin by which mechanism?
Penicillinase producing bacteria exhibit resistance to penicillin by which mechanism?
Which of the following antibacterial agents is derived from a natural source?
Which of the following antibacterial agents is derived from a natural source?
Why is it often easier to develop antibacterial drugs that are selectively toxic compared to antiviral drugs?
Why is it often easier to develop antibacterial drugs that are selectively toxic compared to antiviral drugs?
Methicillin-resistant Staphylococcus aureus (MRSA) strains have resistance due to which mechanism?
Methicillin-resistant Staphylococcus aureus (MRSA) strains have resistance due to which mechanism?
An antimicrobial drug inhibits bacterial cell wall synthesis by blocking the cross-linking of peptidoglycans. Which of the following is the MOST likely target of this drug?
An antimicrobial drug inhibits bacterial cell wall synthesis by blocking the cross-linking of peptidoglycans. Which of the following is the MOST likely target of this drug?
Which antibiotic inhibits protein synthesis and can be resisted by bacteria through a mutation of the ribosomal binding site?
Which antibiotic inhibits protein synthesis and can be resisted by bacteria through a mutation of the ribosomal binding site?
A bacterium has developed resistance to fluoroquinolones. Which mechanism is most likely responsible for this resistance?
A bacterium has developed resistance to fluoroquinolones. Which mechanism is most likely responsible for this resistance?
Which of the following mechanisms of genetic transfer in bacteria involves direct cell-to-cell contact?
Which of the following mechanisms of genetic transfer in bacteria involves direct cell-to-cell contact?
A patient is experiencing nausea, vomiting, and abdominal pain after starting an antibiotic. Which antibiotic is LEAST likely to be the cause, based solely on these side effects?
A patient is experiencing nausea, vomiting, and abdominal pain after starting an antibiotic. Which antibiotic is LEAST likely to be the cause, based solely on these side effects?
Why is the development of antiviral agents more challenging compared to antibacterial agents?
Why is the development of antiviral agents more challenging compared to antibacterial agents?
An antiviral drug is designed to interfere with the virus life cycle. Which of the following steps could be a potential target for the drug?
An antiviral drug is designed to interfere with the virus life cycle. Which of the following steps could be a potential target for the drug?
A patient requires medication for a localized fungal infection. What is a key characteristic of antifungal agents that would be most relevant in this scenario?
A patient requires medication for a localized fungal infection. What is a key characteristic of antifungal agents that would be most relevant in this scenario?
A new antibiotic inhibits pteridine synthetase and dihydrofolate reductase. Which process is most directly affected by this antibiotic?
A new antibiotic inhibits pteridine synthetase and dihydrofolate reductase. Which process is most directly affected by this antibiotic?
Flashcards
Antimicrobial Agents
Antimicrobial Agents
Chemotherapeutic agents with selective toxicity towards pathogens, not the host.
Antibacterial Agents
Antibacterial Agents
Agent that inhibits bacterial growth or kills bacteria.
Bactericidal Agents
Bactericidal Agents
Kill bacteria directly.
Bacteriostatic Agents
Bacteriostatic Agents
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Antibacterial Agent Action
Antibacterial Agent Action
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Inhibition of Cell Wall Synthesis
Inhibition of Cell Wall Synthesis
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Penicillinases
Penicillinases
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Structural Changes in PBP’s
Structural Changes in PBP’s
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Inhibition of Protein Synthesis
Inhibition of Protein Synthesis
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Inhibition of Folic Acid Synthesis
Inhibition of Folic Acid Synthesis
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Transformation (Genetic Transfer)
Transformation (Genetic Transfer)
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Transduction (Genetic Transfer)
Transduction (Genetic Transfer)
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Conjugation (Genetic Transfer)
Conjugation (Genetic Transfer)
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Antiviral Agents
Antiviral Agents
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Antifungal Agents
Antifungal Agents
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Inhibit attachment
Inhibit attachment
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Study Notes
- Lecture focuses on antimicrobial agents, their classifications, mechanisms of action, antibiotic resistance, and side effects of excessive antibiotic use.
Antimicrobial Agents/Drugs
- Chemotherapeutic agents/or drugs exhibit selective toxicity, targeting pathogens while sparing host cells.
- Distinguished from disinfectants and antiseptics, which can harm both pathogens and hosts.
- Antimicrobial agents are categorized into:
- Antibacterial/antibiotics
- Antiviral
- Antifungal
- Antiparasitic/Antinematodes
Antibacterial Agents/Drugs
- Agents or substances inhibit bacterial growth or kill bacteria. Considered synonymous with "antibiotics".
- The term "antibiotic" was first used in 1942 by Selman Waksman.
Classification of Antibacterial Agents
- Based on chemical/biosynthetic origin:
- Natural (e.g., penicillin)
- Semi-synthetic
- Synthetic (e.g., Sulfanilamide)
- Based on biological activity/effect on microorganisms:
- Bactericidal agents kill bacteria.
- Bacteriostatic agents slow down or stop/inhibit bacterial growth.
Bacterial Cell
- Antibacterial agents act selectively against bacterial cells rather than host cells.
- Action is based on the structural and biosynthetic pathway differences between bacterial and animal cells.
How Antibiotics Work
- Rifamycins target the capsule.
- Polymyxins and Sulfonamides work on the Cytoplasm.
- Chloramphenicol, Streptomycin, and tetracyclines affect Ribosomes.
- Penicillins, Cephalosporins, and cycloserine affect the cell wall.
Mechanism of Antibiotic Actions
- Inhibition of cell wall synthesis:
- Penicillins
- Cephalosporins
- Imipenem
- Meropenem
- Aztreonam
- Vancomycin
- Inhibition of bacterial protein synthesis:
- Aminoglycosides
- Chloramphenicol
- Macrolides
- Tetracycline
- Streptogramins
- Linezolid
- Inhibition of nucleic acid synthesis:
- Fluoroquinolones
- Rifampin
- Inhibition of folic acid synthesis:
- Sulfonamides
- Trimethoprim
- Pyrimethamine
Inhibition of Cell Wall Synthesis
- Accomplished by penicillins, cephalosporins, and vancomycin.
- These are bactericidal
- Beta-lactam ring in these antibiotics binds to and blocks penicillin-binding proteins (PBPs), disrupting peptidoglycan layer cross-linking.
Mechanism of Resistance
- Resistance occurs through:
- Penicillinases breakdown of the beta-lactam ring structure produced by staphylococci
- Structural changes in PBPs, observed in MRSA and S. pneumoniae cephalosporin resistance.
Inhibition of Protein Synthesis
- Achieved by erythromycin, chloramphenicol, tetracycline, and streptomycin.
- These agents can be bactericidal or bacteriostatic.
- Resistance occurs through mutation of the ribosomal binding site and enzymatic modification of the antibiotic.
Inhibition of Nucleic Acid Synthesis
- The following is completed by Fluoroquinolones and Rifampin
- These agents are bacteriocidal
- They can inhibit DNA gyrase or RNA polymerase.
- Resistance is caused by alteration of the alpha subunit of DNA gyrase or the beta subunit of RNA polymerase.
Inhibition of Folic Acid Synthesis
- Sulfonamides and pyrimethamine are used
- These are bacteriostatic
- The action is to bind and block key enzymes (pteridine synthetase and dihydrofolate reductase) in folic acid synthesis.
- Resistance emerges from mutations in the dihydrofolate reductase gene, which reduces binding affinity.
Antibiotic Resistance
- Occurs through the genetic transfer of resistance genes via:
- Transformation
- Transduction
- Conjugation
Antibiotic Side-Effects
- Sulfonamides:
- Nausea/vomiting
- Diarrhea
- Anorexia
- Abdominal pain
- Rash
- Photosensitivity
- Headache
- Dizziness
- Tetracyclines:
- Nausea/vomiting
- Diarrhea
- Anorexia
- Abdominal pain
- Tooth discoloration in children under 8 years
- Possible liver toxicity
- Quinolones:
- Nausea/vomiting
- Diarrhea
- Abdominal pain
- Headache
- Lethargy
- Insomnia
- Photosensitivity
Antiviral Agents
- Chemotherapeutic drugs treat viral infections but differ from antibiotics.
- Antiviral agents are:
- Difficult to develop
- Use host metabolism
- Pose a major problem with toxicity
- Antivirals interfere with the virus life cycle without harming the host.
Antifungal Agents
- Chemotherapeutic drugs treat fungal infections.
- They treat localised or systemic infections.
- Some can be purchased over-the-counter.
- Drug availability is limited.
Antifungal Targets
- Fungal Cell Wall:
- β-(1,3)-D-Glucan synthase
- Chitin Synthase
- Mannoprotein
- Fungal Cell Membrane:
- Lanosterol 14α-demethylase
- Squalene Epoxidase
- Inositol Phosphoceramide Synthase
- DNA and Protein Synthesis:
- N-myristoyltransferase
- Aminoacyl-tRNA Synthetase
- Elongation Factor
- Secreted Aspartic Proteinase
- Topoisomerase
- Signal Transduction Pathways:
- Calcineurin
- Electron transport chain
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Description
Explore the mechanisms of action of antimicrobial drugs and their effects on microorganisms. Learn about selective toxicity, resistance mechanisms like penicillinase, and differences between bactericidal and bacteriostatic agents. Understand how drugs target peptidoglycan synthesis and other bacterial processes.
