Antibiotics and Their Mechanisms
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Questions and Answers

Streptomycin binds to the 50S subunit of the bacterial ribosome.

False (B)

Chloramphenicol exerts a bactericidal effect by destroying bacterial cells.

False (B)

Animal cells can synthesize their own folic acid.

False (B)

Sulfonamides competitively inhibit the synthesis of folic acid by mimicking para aminobenzoic acid (PABA).

<p>True (A)</p> Signup and view all the answers

Fluoroquinolones affect the synthesis of RNA in bacterial cells.

<p>False (B)</p> Signup and view all the answers

Broad spectrum antibiotics are effective only against Gram-positive bacteria.

<p>False (B)</p> Signup and view all the answers

Narrow spectrum antibiotics target a wide range of bacterial species.

<p>False (B)</p> Signup and view all the answers

Beta lactam antibiotics require that bacterial cells be actively growing to exert their toxicity.

<p>True (A)</p> Signup and view all the answers

Penicillins contain a four-membered beta lactam ring in their chemical structure.

<p>True (A)</p> Signup and view all the answers

Glycopeptides like vancomycin work by binding to the end of peptide chains in peptidoglycan precursors.

<p>True (A)</p> Signup and view all the answers

Polymyxin is an antibiotic that specifically targets bacterial nucleic acids.

<p>False (B)</p> Signup and view all the answers

A clinically-useful antibiotic should have characteristics that include being inexpensive and easy to produce.

<p>True (A)</p> Signup and view all the answers

All antibacterial agents are toxic to the host cells.

<p>False (B)</p> Signup and view all the answers

Dihydrofolate reductase is responsible for the conversion of Dihydrofolic acid to Thymidine.

<p>False (B)</p> Signup and view all the answers

Alteration of membrane permeability can prevent an antimicrobial agent from entering a bacterial cell.

<p>True (A)</p> Signup and view all the answers

Multiple drug resistance can only occur through chromosomal genes, not plasmids.

<p>False (B)</p> Signup and view all the answers

Methicillin-resistant Staphylococcus aureus (MRSA) is resistant to traditional antibiotic therapies.

<p>True (A)</p> Signup and view all the answers

Efflux pumps actively remove drugs from the cell, contributing to bacterial resistance.

<p>True (A)</p> Signup and view all the answers

The mechanism of infection prevention states that only one type of antimicrobial should be used for every infection.

<p>False (B)</p> Signup and view all the answers

Hydrogen peroxide is more stable and less expensive than chlorine.

<p>False (B)</p> Signup and view all the answers

Bacteria can become resistant by developing a new metabolic pathway that bypasses the actions of an antimicrobial agent.

<p>True (A)</p> Signup and view all the answers

Beta-lactamases are a type of efflux pump that prevents antimicrobial drugs from entering bacteria.

<p>False (B)</p> Signup and view all the answers

Quaternary ammonium compounds are effective sporicides.

<p>False (B)</p> Signup and view all the answers

Aldehydes can inactivate nucleic acids and proteins.

<p>True (A)</p> Signup and view all the answers

Organic acids, such as benzoic acid, can stimulate microbial metabolism.

<p>False (B)</p> Signup and view all the answers

Ethylene oxide is used to sterilize heat-sensitive equipment.

<p>True (A)</p> Signup and view all the answers

Pharmacodynamics refers to the study of what the drug does to the body.

<p>True (A)</p> Signup and view all the answers

Combination therapy is only used to reduce the duration of treatment.

<p>False (B)</p> Signup and view all the answers

Pharmacokinetics studies what the body does to the drug, including its absorption and excretion.

<p>True (A)</p> Signup and view all the answers

Beta-lactamase is a type of antibacterial agent.

<p>False (B)</p> Signup and view all the answers

Phenol is commonly used today as a skin disinfectant due to its effectiveness.

<p>False (B)</p> Signup and view all the answers

Alcohols are effective against endospores.

<p>False (B)</p> Signup and view all the answers

Hypochlorous acid is formed when chlorine is mixed with water.

<p>True (A)</p> Signup and view all the answers

Heavy metals exert their biocidal effect through a process called oligodynamic action.

<p>True (A)</p> Signup and view all the answers

Chemical agents that are bacteriostatic completely eliminate pathogenic bacteria.

<p>False (B)</p> Signup and view all the answers

Zinc chloride is commonly used in mouthwashes.

<p>True (A)</p> Signup and view all the answers

Ozone is used to produce hydroxyl-free radicals that damage proteins and DNA.

<p>False (B)</p> Signup and view all the answers

Flashcards

Antimicrobial

A substance that kills or inhibits the growth of microorganisms.

Broad Spectrum Antibiotic

An antibiotic that is effective against a wide range of both Gram-positive and Gram-negative bacteria.

Narrow Spectrum Antibiotic

An antibiotic that is mainly effective against either Gram-positive or Gram-negative bacteria.

Limited Spectrum Antibiotic

An antibiotic that is effective against a single organism or disease.

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Cell Wall Synthesis Inhibitors

Antibiotics that work by interfering with the synthesis of peptidoglycan, a crucial component of bacterial cell walls.

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Beta-lactam Antibiotics

A class of antibiotics that contain a 4-membered beta-lactam ring. They include penicillins, cephalosporins, and carbapenems.

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Glycopeptides (e.g., Vancomycin)

Antibiotics that block cell wall synthesis by binding to the end of peptidoglycan precursors, preventing their incorporation into the cell wall.

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Cell Membrane Inhibitors

Antibiotics that disrupt the structure or function of bacterial membranes.

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Protein Synthesis Inhibitors

Antibiotics that target bacterial ribosomes (70S), preventing the synthesis of proteins essential for bacterial growth.

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Tetracyclines

Broad-spectrum antibiotics targeting bacterial ribosomes, effective against both Gram-positive and Gram-negative bacteria.

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Chloramphenicol

A broad-spectrum antibiotic that exerts a bacteriostatic effect, meaning it stops bacteria from multiplying.

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Streptomycin

An aminoglycoside antibiotic targeting the 30S subunit of the bacterial ribosome, interfering with protein synthesis.

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Fluoroquinolone

Antibiotics interfering with the synthesis of DNA or RNA in bacteria, preventing them from replicating.

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Bacteriostatic Agent

A chemical that prevents the growth and multiplication of bacteria without killing them.

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Bactericidal Agent

A chemical that kills bacteria directly.

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Oligodynamic Action

The biocidal effect of heavy metals, where even small amounts can kill microorganisms.

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Phenol

A disinfectant that disrupts cell membranes and precipitates proteins, often used historically but rarely today.

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Alcohol

A disinfectant that dissolves membrane lipids and coagulates proteins, used to sterilize surfaces and skin before injections.

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Halogens

Effective disinfectants that denature proteins, like iodine and chlorine.

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Hypochlorous Acid

A powerful disinfectant formed when chlorine reacts with water, commonly used in swimming pools and water treatment.

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Oxidizing Agents

Disinfectants that damage proteins and DNA by producing highly reactive hydroxyl free radicals.

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Antimicrobial Resistance Mechanisms

Bacteria develop ways to resist antibiotics, like changing their target site, destroying the drug, or preventing its entry.

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Target Site Alteration

Bacteria modify the part of their cell that an antibiotic targets, making the drug less effective. This could involve changes to enzymes or ribosomes.

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Restricted Transport

Bacteria change their membrane proteins to block the antibiotic from entering their cells, or they actively pump the drug out.

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Enzymatic Destruction

Bacteria produce enzymes to break down the antibiotic, rendering it useless. An example is penicillinase.

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Metabolic Bypass

Bacteria develop a new metabolic pathway to circumvent the antibiotic's effect. They find an alternate way to do what the antibiotic was blocking.

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Efflux Pumps

Bacteria use pumps to actively remove drugs from their cells before the drugs can affect them.

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Multi-Drug Resistance (MDR)

Bacteria become resistant to multiple classes of antibiotics, making them harder to treat.

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Preventing Antimicrobial Resistance

Using appropriate antibiotics, identifying the specific bacteria causing infection, and limiting unnecessary use of antibiotics.

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Hydrogen Peroxide

A disinfectant used for both inanimate objects and as an antiseptic. More effective than chlorine but less stable and expensive.

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Quaternary Ammonium Compounds

Cationic detergents that disrupt cell membranes. Used as disinfectants and skin antiseptics, but not effective against spores.

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Aldehydes

Chemicals like formaldehyde and glutaraldehyde that inactivate proteins and nucleic acids. Used as disinfectants.

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Organic Acids

Chemicals like benzoic acid that inhibit the growth of bacteria and molds. Used as food preservatives.

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Ethylene Oxide

A gas used for sterilization of heat-sensitive materials. It inactivates nucleic acids and proteins.

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Prophylaxis

Preventive measures taken to avoid a disease or infection.

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Chemoprophylaxis

Using medication to prevent disease or infection.

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Pharmacology

The scientific study of drugs and their effects on living systems.

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Study Notes

Antimicrobial Agents

  • Antimicrobials interfere with vital structures and processes of microorganisms to kill or inhibit their growth.
  • Broad-spectrum antibiotics act against a wide range of Gram-positive and Gram-negative bacteria.
  • Narrow-spectrum antibiotics are effective against either Gram-positive or Gram-negative bacteria.
  • Limited-spectrum antibiotics target a single organism or disease.
  • A clinically useful antibiotic should have a wide spectrum of activity, be non-toxic and non-allergenic to the host.
  • It should not eliminate the normal flora of the host, reach the area of infection and be easy to produce and stable.
  • Microbial resistance to the antibiotic should be uncommon and unlikely to develop.

Classification of Antibacterials

  • Antibacterials can be categorized based on their site of action and molecular structure.
  • Cell wall synthesis inhibitors: Inhibit steps in bacterial peptidoglycan synthesis.
    • Generally effective against eubacteria, as human cells lack rigid cell walls
    • Beta-lactams (e.g., penicillins, cephalosporins, carbapenems):
      • Contain a 4- or 6-membered ring.
      • Inhibit carboxypeptidase and transpeptidase enzymes.
      • Bactericidal and require active bacterial growth.
    • Glycopeptides (e.g., vancomycin): Block cell wall synthesis by binding to the end of peptide chains.

Other Inhibitors

  • Cell membrane inhibitors: Disrupt bacterial membrane structure or function, example: Polymyxin.
  • Protein synthesis inhibitors: Target 70S ribosomes (bacterial)
    • Tetracyclines, chloramphenicol, macrolides (e.g., erythromycin), and aminoglycosides (e.g., streptomycin).
  • Nucleic acid inhibitors: Affect DNA or RNA synthesis or binding, example: Fluoroquinolones (e.g., ciprofloxacin).
  • Competitive inhibitors: These agents compete with essential metabolites for bacterial enzymes responsible for folic acid synthesis (e.g., sulfonamides, trimethoprim).

Mechanisms of Antimicrobial Resistance

  • Mechanisms of bacterial resistance mechanisms include:
    • Altering the target site to decrease antibiotic affinity.
    • Destroying or inactivating the antibiotic.
    • Limiting antibiotic uptake into the cell.
    • Developing alternative metabolic pathways.
    • Using efflux pumps to remove the antibiotic from the cell.
    • Producing a bacterial protein to shield the target site.

Prevention of Antimicrobial Resistance

  • To prevent resistance:
    • Prescribe the correct antibiotic for the infection.
    • Identify the causative organism.
    • Choose narrow-spectrum instead of broad-spectrum antimicrobials.
    • Maintain correct treatment duration.
    • Use appropriate dosages.

Chemical Methods of Microbial Control

  • Chemicals can be bacteriostatic (preventing growth) or bactericidal (killing).
  • Factors influencing effectiveness include population size, type of organism, concentration, duration of exposure, temperature, pH, organic matter, and biofilm formation.

Disinfectants and Antiseptics

  • Phenol (carbolic acid): Disrupts cell membranes and precipitates proteins; rarely used today due to skin irritation.
  • Alcohols: Kill most bacteria, fungi, but not endospores; dissolve membrane lipids and coagulate proteins.
  • Halogens (e.g., iodine, chlorine): Denature proteins; iodine used as tincture, chlorine used to disinfect water.
  • Heavy metals (e.g., silver, copper, zinc): Oligodynamic action, precipitate proteins.
  • Oxidizing agents (e.g., ozone, hydrogen peroxide): Produce free radicals that damage proteins and DNA.
  • Quaternary ammonium compounds: Alter cell permeability; used as disinfectants and antiseptics.
  • Aldehydes (e.g., formaldehyde, glutaraldehyde): React chemically with nucleic acids and proteins, inactivating them.
  • Organic acids (e.g., benzoic acid): Inhibit microbial metabolism, commonly used as food preservatives.
  • Gaseous sterilization (e.g., ethylene oxide): Used to sterilize heat-sensitive equipment and materials; inactivates nucleic acids and proteins.

Prophylaxis and Pharmacology

  • Prophylaxis: Treatment given to prevent disease or infection.
  • Chemoprophylaxis: Use of medication to prevent a disease or infection.
  • Alternative medicine: Treatments outside conventional medicine.
  • Complementary medicine: Use of alternative therapies with conventional treatments.
  • Combination therapy (polytherapy): Use of more than one medication to treat an infection.
  • Pharmacology: Study of drug action, divided into pharmacodynamics and pharmacokinetics.
  • Pharmacodynamics: Study of the drug's effect on the body.
  • Pharmacokinetics: Study of how the body processes a drug (absorption, distribution, metabolism, elimination).

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Description

This quiz covers various antibiotics, their mechanisms of action, and the types of bacteria they target. Understand the differences between broad-spectrum and narrow-spectrum antibiotics and learn about specific compounds like penicillins and glycopeptides. Test your knowledge on how these medications affect bacterial growth and metabolism.

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