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Questions and Answers
Why are antibacterial drugs more prevalent and diverse compared to antiviral or anti-eukaryotic drugs?
Why are antibacterial drugs more prevalent and diverse compared to antiviral or anti-eukaryotic drugs?
- Eukaryotic and viral pathogens mutate at a slower rate, reducing the need for drug development.
- Antiviral and anti-eukaryotic drugs are more stringently regulated due to their higher toxicity.
- The unique cellular structures and processes in bacteria offer more specific targets with less risk of affecting host cells. (correct)
- Research funding is disproportionately allocated towards antibacterial drug development due to the higher incidence of bacterial infections.
A novel antibiotic is developed that inhibits the function of prokaryotic ribosomes, but it also shows some affinity for mitochondrial ribosomes. What is the most likely explanation for this cross-reactivity?
A novel antibiotic is developed that inhibits the function of prokaryotic ribosomes, but it also shows some affinity for mitochondrial ribosomes. What is the most likely explanation for this cross-reactivity?
- Mitochondrial ribosomes are structurally more similar to eukaryotic ribosomes than prokaryotic ribosomes.
- The antibiotic is modified by the host cell, creating a metabolite that targets eukaryotic ribosomes.
- The antibiotic is poorly targeted and interacts with any ribosome regardless of origin.
- Mitochondria evolved from bacteria and retain ribosomes similar to prokaryotic ribosomes. (correct)
A researcher is developing a new drug that targets the synthesis of fungal cell walls. Which of the following would be the MOST appropriate target for this drug?
A researcher is developing a new drug that targets the synthesis of fungal cell walls. Which of the following would be the MOST appropriate target for this drug?
- Ergosterol
- Peptidoglycan
- Lipopolysaccharide (LPS)
- Chitin (correct)
Why are humans less susceptible to drugs that target ergosterol, a component of fungal membranes, compared to fungi?
Why are humans less susceptible to drugs that target ergosterol, a component of fungal membranes, compared to fungi?
A Gram-positive bacterial strain has developed resistance to vancomycin by altering its peptidoglycan structure. Which mechanism is MOST likely responsible for this resistance?
A Gram-positive bacterial strain has developed resistance to vancomycin by altering its peptidoglycan structure. Which mechanism is MOST likely responsible for this resistance?
Why is bacitracin, which blocks the transport of NAG and NAM across the cytoplasmic membrane, primarily effective against Gram-positive bacteria?
Why is bacitracin, which blocks the transport of NAG and NAM across the cytoplasmic membrane, primarily effective against Gram-positive bacteria?
A patient is diagnosed with a systemic fungal infection. The causative agent is identified as a species that produces large quantities of polysaccharides in its cell wall. Which antifungal drug class would be MOST effective in treating this infection?
A patient is diagnosed with a systemic fungal infection. The causative agent is identified as a species that produces large quantities of polysaccharides in its cell wall. Which antifungal drug class would be MOST effective in treating this infection?
A new antiviral drug is designed to interfere with the function of viral reverse transcriptase. While effective in vitro, the drug shows limited efficacy in clinical trials. What is the MOST likely reason for this discrepancy?
A new antiviral drug is designed to interfere with the function of viral reverse transcriptase. While effective in vitro, the drug shows limited efficacy in clinical trials. What is the MOST likely reason for this discrepancy?
A research team discovers a new bacterial species that is resistant to most known antibiotics. Further investigation reveals that the bacteria possess a novel enzyme that modifies aminoglycosides, preventing them from binding to the ribosome. What type of resistance mechanism is MOST likely at play?
A research team discovers a new bacterial species that is resistant to most known antibiotics. Further investigation reveals that the bacteria possess a novel enzyme that modifies aminoglycosides, preventing them from binding to the ribosome. What type of resistance mechanism is MOST likely at play?
A patient is prescribed a new antimicrobial drug. Prior to prescribing, the doctor learns the patient is also taking medication to suppress their immune system. What consideration regarding antimicrobial agents would be MOST important in this scenario?
A patient is prescribed a new antimicrobial drug. Prior to prescribing, the doctor learns the patient is also taking medication to suppress their immune system. What consideration regarding antimicrobial agents would be MOST important in this scenario?
Flashcards
Drugs
Drugs
Chemicals that affect physiology in any manner
Chemotherapeutic agents
Chemotherapeutic agents
Drugs that act against diseases
Antimicrobial agents
Antimicrobial agents
Drugs that treat infections
Bacteriostatic
Bacteriostatic
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Bactericidal
Bactericidal
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Inhibition of Cell Wall Synthesis
Inhibition of Cell Wall Synthesis
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Inhibition of Cell Wall Synthesis in Fungi
Inhibition of Cell Wall Synthesis in Fungi
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Inhibition of Protein Synthesis
Inhibition of Protein Synthesis
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Inhibition of Nucleic Acid Synthesis
Inhibition of Nucleic Acid Synthesis
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Disruption of Cytoplasmic Membranes
Disruption of Cytoplasmic Membranes
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Study Notes
- Drugs are chemicals that affect physiology in any manner
- Chemotherapeutic agents are drugs that act against diseases
- Antimicrobial agents (antimicrobials) are drugs that treat infections
The History of Antimicrobial Agents
- Paul Ehrlich created the idea of ""Magic bullets""
- Alexander Fleming discovered that arsenic compounds killed microbes
- Penicillin was discovered by Alexander Fleming and released from Penicillium
- Gerhard Domagk discovered sulfanilamide
- Selman Waksman coined the term ""Antibiotics""
- Antimicrobial agents are produced naturally by organisms
- Selman Waksman discovered Streptomycin, which cured tuberculosis
The History of Antimicrobial Agents (continued)
- Semisynthetics are chemically altered antibiotics that are more effective, longer lasting, or easier to administer than naturally occurring ones
- Synthetics are antimicrobials that are completely synthesized in a lab
Mechanisms of Antimicrobial Action
- Successful chemotherapy requires selective toxicity
- Antibacterial drugs constitute the largest number and diversity of antimicrobial agents
- Fewer drugs exist to treat eukaryotic infections, and antiviral drugs are limited
Antimicrobial Agents
- It's important to understand mechanisms of action and be able to speak to the consequences to a microbe given a certain mechanism of action
Bacteriostatic vs Bactericidal
- Bacteriostatic drugs prevent the growth of bacteria but do not kill them
- The host's immune system will do the rest with killing the bacteria
- Bactericidal drugs kill bacteria
Mechanisms of Antimicrobial Action: Inhibition of Cell Wall Synthesis
- Inhibition of synthesis of bacterial walls
- Most common agents prevent cross-linkage of NAM subunits
- Beta-lactams are most prominent in this group, and their functional groups are beta-lactam rings
- Beta-lactams bind to enzymes that cross-link NAM subunits
- Bacteria have weakened cell walls and eventually lyse
Mechanisms of Antimicrobial Action: Inhibition of Cell Wall Synthesis (Beta-lactam derivatives)
- Semisynthetic derivatives of beta-lactams
- More stable in acidic environments and more readily absorbed
- Less susceptible to deactivation
- More active against more types of bacteria
Mechanisms of Antimicrobial Action: Inhibition of Cell Wall Synthesis (Examples)
- Vancomycin and cycloserine interfere with particular bridges that link NAM subunits in many Gram-positive bacteria
- Bacitracin blocks transport of NAG and NAM from cytoplasm
- Isoniazid and ethambutol disrupt mycolic acid formation in mycobacterial species
Mechanisms of Antimicrobial Action: Inhibition of Cell Wall Synthesis (General)
- Prevent bacteria from increasing the amount of peptidoglycan
- Have no effect on existing peptidoglycan layer
- Effective only for growing cells
Mechanisms of Antimicrobial Action: Inhibition of Cell Wall Synthesis (Fungal)
- Inhibition of synthesis of fungal walls
- Fungal cells are composed of various polysaccharides not found in mammalian cells
- Echinocandins inhibit the enzyme that synthesizes glucan
Mechanisms of Antimicrobial Action: Inhibition of Protein Synthesis
- Interference with prokaryotic ribosomes
- Prokaryotic ribosomes are 70S (30S and 50S)
- Eukaryotic ribosomes are 80S (40S and 60S)
- A ribosome is composed of a small and large subunit
- Drugs selectively target translation
- Mitochondria of animals and humans contain 70S ribosomes and so drugs can be harmful
Mechanisms of Antimicrobial Action: Inhibition of Protein Synthesis (tRNA Interference)
- Interference with charging (attaching amino acids) of transfer RNA molecules
- Aminoscyl-tRNA synthetases load amino acids onto tRNA molecules
- Mupirocin selectively binds to isoleucyl-tRNA synthetase
- Prevents loading of isoleucine only in Gram-positive bacteria
Mechanisms of Antimicrobial Action: Disruption of Cytoplasmic Membranes
- Some drugs form channels through the cytoplasmic membrane and damage its integrity
- Nystatin and amphotericin B attach to ergosterol in fungal membranes
- Humans are somewhat susceptible because cholesterol is similar to ergosterol
- Bacteria lack sterols, so they are not susceptible
Mechanisms of Antimicrobial Action: Disruption of Cytoplasmic Membranes (Examples)
- Azoles and allylamines inhibit ergosterol synthesis
- Polymyxin disrupts cytoplasmic membranes of Gram-negative bacteria
- Toxic to human kidneys
- Some parasitic drugs act against cytoplasmic membranes
Mechanisms of Antimicrobial Action: Inhibition of Nucleic Acid Synthesis
- Several drugs block DNA replication or RNA transcription
- Drugs often affect both eukaryotic and prokaryotic cells
- Are not normally used to treat infections
- Used in research and perhaps to slow cancer cell replication
Mechanisms of Antimicrobial Action: Inhibition of Nucleic Acid Synthesis (Examples)
- Quinolones and fluoroquinolones act against prokaryotic DNA gyrase
- Nucleotide or nucleoside analogs interfere with the function of nucleic acids
- These distort shapes of nucleic acid molecules and prevent further replication, transcription, or translation
- Most often used against viruses
- Effective against rapidly dividing cancer cells
Mechanisms of Antimicrobial Action: Inhibition of Nucleic Acid Synthesis (RNA)
- Inhibitors of RNA polymerase
- Reverse transcriptase inhibitors
- Reverse transcriptase is only found in viruses called retroviruses
- Act against an enzyme HIV uses in its replication cycle
- Does not harm people because humans lack reverse transcriptase
Mechanisms of Antimicrobial Action: Inhibition of Metabolic Pathways
- Antimetabolic agents can be effective when pathogen and host metabolic processes differ
- Atovaquone interferes with electron transport in protozoa and fungi
- Heavy metals inactivate enzymes
- Agents disrupt tubulin polymerization and glucose uptake by many protozoa and parasitic worms
- Drugs block activation of viruses
- Metabolic antagonists
Mechanisms of Antimicrobial Action: Inhibition of Metabolic Pathways (Examples)
- Trimethoprim also interferes with nucleotide synthesis
- Antiviral agents can target unique aspects of viral metabolism
- Amantadine, rimantadine, and weak organic bases prevent viral uncoating
- Protease inhibitors interfere with an enzyme that HIV needs in its replication cycle
Mechanisms of Antimicrobial Action: Prevention of Virus Attachment, Entry, or Uncoating
- Attachment antagonists block viral attachment or receptor proteins
- This is a new area of antimicrobial drug development
- Pleconaril blocks viral attachment, and Arildone prevents viral uncoating
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