Ch_20_lecture

First successful antimicrobial agent

Salvarsan, developed by Paul Ehrlich in 1910 for treating syphilis.

First antibiotic discovered

Penicillin, discovered by Alexander Fleming in 1928.

Chemotherapeutic agent

Any drug used to treat disease, especially cancer and infections.

Antimicrobial drug or agent

A substance that kills or inhibits the growth of microorganisms.

Semisynthetic

A drug that is chemically modified after being isolated from natural sources.

Antibiotic

A type of antimicrobial drug that specifically targets bacteria.

Selective toxicity

The property of antimicrobial drugs to cause greater harm to pathogens than to host cells.

Bacteriostatic

Drugs that inhibit bacterial growth but do not kill bacteria; the host's immune system must eliminate the bacteria.

Bactericidal

Drugs that kill bacteria directly.

Broad-spectrum antimicrobials

Drugs that are effective against a wide range of bacteria, both gram-positive and gram-negative.

Narrow-spectrum antimicrobials

Drugs that are effective against a limited range of bacteria.

Synergistic

A relationship where the effect of two drugs together is greater than the sum of their individual effects.

Antagonistic

A relationship where one drug interferes with the action of another.

Additive

A relationship where the effect of two drugs together is equal to the sum of their individual effects.

Adverse effects of antimicrobial agents

1. Allergic reactions; 2. Toxicity; 3. Disruption of normal microbiota.

Microbial resistance

The ability of bacteria to survive and multiply despite the presence of antimicrobial drugs, causing treatment failures.

Modes of action of major antibacterial drugs

1. Inhibition of cell wall synthesis;

2. 2. Inhibition of protein synthesis;

3. 3. Inhibition of nucleic acid synthesis;

4. 4. Inhibition of metabolic pathways;

5. 5. Interference with cell membrane function;

6. 6. Interference with Mycobacterium tuberculosis metabolism

Laboratory determination of bacterial sensitivity

Methods include testing for minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) and using diffusion techniques like Kirby-Bauer assay.

Minimum inhibitory concentration (MIC)

The lowest concentration of an antimicrobial that prevents visible growth of a microorganism.

Minimum bactericidal concentration (MBC)

The lowest concentration of an antimicrobial that kills 99.9% of bacteria.

Diffusion bioassay

A method used to determine the susceptibility of bacteria to antibiotics by measuring inhibition zones.

Kirby-Bauer disc diffusion

A standard method for testing the effectiveness of antibiotics on specific bacteria using discs infused with antibiotics.

Major antifungal drugs' modes of action

1. Disruption or damage of cell membrane;

2. Inhibition of nucleic acid synthesis.

Who discovered Penicillin, the first antibiotic?

Penicillin was discovered by Alexander Fleming in 1928.

What defines a chemotherapeutic agent?

A chemotherapeutic agent is any chemical used to treat a disease, especially infections, by destroying or inhibiting the growth of pathogens.

What are some characteristics of an antimicrobial drug?

An antimicrobial drug is designed to kill or inhibit the growth of microorganisms, including bacteria, viruses, fungi, and parasites.

Why is tissue distribution important for an antimicrobial agent?

Tissue distribution determines whether the drug reaches the infection site effectively, impacting its therapeutic outcome.

How do metabolic pathways relate to antimicrobial therapy?

Inhibition of metabolic pathways can effectively disrupt essential microbial functions, leading to cell death.

What is the difference between synergistic and additive drug effects?

Synergistic effects occur when the combined action of drugs is greater than the sum of their individual effects, while additive effects result in a combined effect equal to the sum of the individual effects.

What role does selective toxicity play in antimicrobial treatment?

Selective toxicity allows an antimicrobial agent to target pathogens without harming the host's cells, minimizing side effects.

What is a common mechanism of action for beta-lactam antibiotics?

Beta-lactam antibiotics work by inhibiting cell wall synthesis in bacteria, leading to cell lysis and death.

What factors contribute to the development of microbial resistance?

Factors include overuse of antibiotics, incomplete courses of treatment, and genetic mutations that confer resistance.

What is the significance of adverse effects in antimicrobial drug development?

Adverse effects can deter the use of an antimicrobial agent and require careful monitoring to ensure patient safety.

How does the minimum inhibitory concentration (MIC) inform treatment decisions?

MIC helps determine the lowest dose of an antimicrobial that effectively inhibits growth, guiding appropriate dosing.

What does the Kirby-Bauer method assess in antimicrobial susceptibility testing?

The Kirby-Bauer method assesses the susceptibility of bacteria to antibiotics by measuring the inhibition zones around antibiotic discs.

What types of adverse effects do allergenic reactions encompass?

Allergic reactions can include skin rashes, anaphylaxis, and other immune responses triggered by the drug.

Why is the study of microbial resistance a growing concern in healthcare?

The rise of resistant strains leads to treatment failures, increased healthcare costs, and poses public health risks.

What types of antifungal mechanisms disrupt nucleic acid synthesis?

Some antifungal agents target enzymes involved in the synthesis of DNA or RNA, inhibiting fungal replication.

What defines broad-spectrum antimicrobials?

Broad-spectrum antimicrobials are effective against a wide variety of microorganisms, including both Gram-positive and Gram-negative bacteria.

What does tissue distribution refer to in antimicrobial pharmacology?

Tissue distribution is the ability of a drug to permeate various tissues and fluids in the body, affecting its delivery and action against pathogens.