Antimicrobial Chemotherapy Overview

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Questions and Answers

What is the main goal of antimicrobial chemotherapy?

To eliminate all bacteria from the host

To enhance the efficacy of the host's immune response

To destroy the infective agent without harming the host's cells (correct)

To suppress the immune system to prevent further infection

Which of the following is a common source of antibiotics?

Aerobic bacteria and fungi (correct)

Viral metabolites

Synthetic chemicals only

Plant extracts and minerals

What does the term 'selective toxicity' refer to?

The effectiveness of a drug against a wide range of infections

The capacity of a drug to target specific microbes without harming host cells (correct)

The safety of a drug for human use in high doses

The ability of a drug to kill all types of cells

Which of the following drugs is most likely to have selective toxicity?

Protein synthesis inhibitors Signup and view all the answers

What is a metabolic analog in the context of antimicrobial action?

A compound that mimics natural substances in a microbe's metabolism Signup and view all the answers

Which part of the penicillin structure is responsible for its classification in the antibiotic group?

Beta-lactam ring Signup and view all the answers

What is a significant difference between penicillins and cephalosporins?

Cephalosporins have a different main ring structure. Signup and view all the answers

What is the suffix commonly found in the names of penicillin antibiotics?

-cillin Signup and view all the answers

Which statement about antimicrobial drugs is accurate?

The largest number of antimicrobial drugs target bacterial infections. Signup and view all the answers

What distinguishes the Cephalosporin group in the context of antibiotic use?

They account for the majority of all antibiotics administered today. Signup and view all the answers

What is the preferable therapeutic index for an antimicrobial drug?

A high therapeutic index Signup and view all the answers

What is the purpose of performing a disc diffusion test?

To determine the sensitivity of bacteria to antibiotics Signup and view all the answers

Which method allows for the measurement of the minimum inhibitory concentration (MIC) using a strip?

E-test Signup and view all the answers

Which of the following factors is NOT essential when selecting an antimicrobial drug?

The cost of the drug Signup and view all the answers

How is the size of the zone of inhibition interpreted in a disc diffusion test?

Larger zones indicate higher sensitivity Signup and view all the answers

Which testing method involves examining body fluids for rapid identification of the infectious agent?

Direct examination Signup and view all the answers

What does the control tube in a tube dilution test lack?

Antibiotic Signup and view all the answers

What is indicated by a 'zone of inhibition' in antimicrobial susceptibility testing?

The bacterium is sensitive to the drug Signup and view all the answers

What is the primary goal of antimicrobial drugs?

To selectively disrupt cell processes or structures of microbes Signup and view all the answers

Which of the following mechanisms is NOT one of the actions of antimicrobial drugs?

Promotion of DNA replication Signup and view all the answers

Penicillins and cephalosporins are primarily effective by which mechanism of action?

Inhibiting cell wall synthesis Signup and view all the answers

What effect do bactericidal antibiotics have on bacteria?

They kill bacterial cells directly Signup and view all the answers

Which of the following describes a function of antimicrobial drugs that affect nucleic acid synthesis?

Inhibiting replication of DNA or RNA Signup and view all the answers

How do most antimicrobial drugs achieve selective toxicity?

By targeting processes unique to microbial cells Signup and view all the answers

Which statement about prokaryotic ribosomes in the context of antibiotics is true?

They differ from eukaryotic ribosomes, allowing selective antibiotic action Signup and view all the answers

What is the result of antibiotics blocking translation in bacteria?

Inhibited protein synthesis Signup and view all the answers

What is a primary consequence of damaged cell membranes in microbes?

Death from metabolic disruption or lysis Signup and view all the answers

How do sulfonamides effectively inhibit folic acid synthesis?

Through competitive inhibition by mimicking substrates Signup and view all the answers

What distinguishes broad-spectrum antimicrobials from narrow-spectrum antimicrobials?

Broad-spectrum affects a larger range of microbes Signup and view all the answers

What enzymes are targeted by chemical agents in the metabolic pathway for synthesizing tetrahydrofolic acid?

Dihydropteroate synthase and dihydrofolate reductase Signup and view all the answers

What role do beta-lactamases play in microbial resistance?

They hydrolyze beta-lactam antibiotics Signup and view all the answers

Which of the following is not classified as a beta-lactam antibiotic?

Vancomycin Signup and view all the answers

Which of these antibiotics primarily acts by targeting the cellular membrane?

Polymyxin Signup and view all the answers

Which mechanism is NOT commonly used by microbes to resist antimicrobials?

Increasing nutrient absorption speeds Signup and view all the answers

What distinguishes cephalosporins from penicillins?

Cephalosporins cause fewer allergic reactions than penicillins. Signup and view all the answers

Which of the following is NOT a known beta-lactam antibiotic?

Vancomycin Signup and view all the answers

What is a common application of aminoglycoside drugs?

Treating aerobic gram-negative rods. Signup and view all the answers

How do tetracycline antibiotics work?

They bind to ribosomes and block protein synthesis. Signup and view all the answers

Which generation of cephalosporins typically has the broadest antibacterial activity?

Fourth generation Signup and view all the answers

What type of bacteria can tetracycline antibiotics effectively target?

Aerobic and anaerobic bacteria. Signup and view all the answers

Which aminoglycoside drug is recognized as a potent treatment for bubonic plague?

Streptomycin Signup and view all the answers

What is the function of isoniazid in antibiotic therapy?

Specifically targeting mycobacterial infections. Signup and view all the answers

Study Notes

Chemotherapy

The primary goal of antimicrobial chemotherapy is to administer a drug to an infected person that destroys the infective agent without harming the host's cells.
Achieving this goal is challenging.
Chemotherapeutic agents are described by their origin, effectiveness, and if they are produced naturally or chemically synthesized.

Ideal Antimicrobial Drug Characteristics

Selectively toxic to microbes, but nontoxic to host cells.
Microbicidal rather than microbistatic (killing rather than inhibiting).
Relatively soluble in body fluids, functions even at high dilution.
Remains potent long enough to act and is not broken down or excreted prematurely.
Minimizes development of antimicrobial resistance.
Complements or assists the host's defenses.
Remains active in tissues and body fluids.
Readily delivered to the site of infection.
Reasonably priced.
Does not disrupt the host's health by causing allergies or predisposing the host to other infections.

Terminology of Antimicrobials

Chemotherapeutic drug: Any chemical used in the treatment, relief, or prophylaxis of a disease.
Prophylaxis: Use of a drug to prevent imminent infection in a person at risk.
Antimicrobial chemotherapy: The use of drugs to control infection.
All-inclusive term for any antimicrobial drug: regardless of the type of microorganism it targets.
Antibiotics: Substances produced by natural metabolic processes of microorganisms that can inhibit or destroy microorganisms. Typically used for microbial targets such as bacteria, and not other types of microbes.
Semisynthetic drugs: Drugs chemically modified in a laboratory after isolation from natural sources.
Synthetic drugs: Drugs entirely produced by chemical reactions within a laboratory setting.
Narrow-spectrum (limited spectrum): Antimicrobials effective against a limited array of microbial types.
Broad-spectrum (extended spectrum): Antimicrobials effective against a wide variety of microbial types.

Origins of Antimicrobial Drugs

Antibiotics are often metabolic byproducts of aerobic bacteria and fungi (e.g., streptomyces, bacillus, penicillium, cephalosporium).
Chemists modify naturally occurring antibiotics to create new drugs.
Research continues to find antimicrobial compounds in other species besides bacteria and fungi.

Drug and Microbe Interactions/ Selective Toxicity

Antimicrobial drugs disrupt cell processes or structures of bacteria, fungi, and protozoa or inhibit virus replication.
Most drugs interfere with the function of enzymes needed to synthesize or assemble macromolecules, or destroy existing structures in the cell.
Ideal antimicrobial drugs are selectively toxic, killing or inhibiting microbial cells without damaging host tissues.

Mechanisms of Drug Action

Inhibition of cell wall synthesis
Inhibition of nucleic acid structure and function
Inhibition of protein synthesis
Interference with cell membrane structure or function
Inhibition of folic acid synthesis

Antibacterial Drugs Targeting the Cell Wall

Active cells continuously synthesize and transport peptidoglycan to the cell envelope.
Penicillins and cephalosporins interfere with enzymes necessary for completing this process.
These drugs are considered bactericidal antibiotics.

Antibacterial Drugs Targeting Nucleic Acid Synthesis

Block the synthesis of nucleotides.
Inhibit replication and stop transcription.
Inhibit DNA synthesis.

Antibacterial Drugs Blocking Protein Synthesis

Inhibit translation by reacting with the ribosome-mRNA complex.
Prokaryotic ribosomes are structurally different from eukaryotic ribosomes, creating selective targets for antibacterial drugs.

Antibacterial Drugs Disrupting Cell Membrane Function

Damaged membranes lead to lysis or disruptions in metabolism, resulting in microbial death.
Drug specificity is often based on differences in lipid types in the microbial membrane.

Antibacterial Drugs Inhibiting Folic Acid Synthesis

Sulfonamides and trimethoprim act as competitive inhibitors, preventing the proper substrates from binding to necessary enzymes, leading to the slowing or stopping of cellular metabolism.

Survey of Major Antimicrobial Drug Groups

Distinguish between broad-spectrum and narrow-spectrum antimicrobials.
Understand and trace the evolution of penicillin antimicrobials—their effectiveness against microbes, and their location.
Explain the significance of beta-lactamases.
List other beta-lactam antibiotic classes and examples.
List common cell wall antibiotics that are not beta-lactams.

Considerations in Selecting an Antimicrobial Drug

Understanding microbe type and susceptibility
Evaluating patient's overall condition
Determining susceptibility via methods such as the Kirby-Bauer disc diffusion test or the tube dilution tests
Defining the therapeutic index (ratio of toxic dose to minimum effective dose). A higher therapeutic index is preferred.

Best Choice of Drug

Choose a drug with high selective toxicity to the infectious agent and low toxicity to the human host.
The therapeutic index is crucial: drugs with a higher ratio are safer to use.

Toxicity to Organs and Allergic Responses to Drugs

Drugs can cause toxicity to various organs (e.g., liver, kidneys, gastrointestinal tract, cardiovascular, blood-forming tissue, nervous system, respiratory tract, skin, bones, teeth).
Drugs can cause allergic responses, which are heightened sensitivities to antigens present in drugs that trigger an allergic response.

Suppression and Alteration of the Microbiota by Antimicrobials

Biota refers to the normal colonists (bacteria) that inhabit body surfaces.
Broad-spectrum antimicrobials can destroy beneficial microbes in addition to pathogenic microbes.

Superinfection

When antimicrobials kill beneficial bacteria, microbes that were previously present in small numbers can overgrow and cause a new infection.

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Description

This quiz covers key concepts related to antimicrobial chemotherapy, including the principles of selective toxicity, the sources and classifications of antibiotics, and the differences between various antibiotic groups. Test your understanding of these critical topics in pharmacology and microbiology.