IndietroChapter 12: Drugs, Microbes, Host – The Elements of Chemotherapy
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Drugs, Microbes, Host – The Elements of Chemotherapy
Principles of Antimicrobial Therapy
Antimicrobial chemotherapy is the use of chemical agents to treat infections by destroying or inhibiting the growth of pathogenic microbes without causing harm to the host. The goal is to achieve selective toxicity, where the drug targets the microbe but spares host cells.
Selective toxicity: The drug should harm the microbe, not the host.
Sources: Antimicrobial drugs can be natural, semi-synthetic, or synthetic.
Perfect drug: While an ideal drug is sought, practical use involves balancing efficacy, safety, and other characteristics.
Characteristics of the Ideal Antimicrobial Drug
The ideal antimicrobial drug possesses several key features that maximize its effectiveness and minimize harm to the patient.
Characteristic | Description |
|---|---|
Selective toxicity | Destroys/inhibits microbes without harming host cells |
Microbicidal | Kills microbes rather than merely inhibiting growth |
Potency | Remains active long enough to act; not broken down or excreted prematurely |
Resistance | Not prone to development of microbial resistance |
Host defense | Assists or complements host immune defenses |
Stability | Active even when diluted in body fluids/tissues |
Delivery | Easily delivered to the site of infection |
Cost | Reasonably priced |
Side effects | Does not cause allergies or predispose to other infections |
Sources of Antimicrobial Drugs
Many antibiotics are natural metabolic products of certain bacteria and fungi, which use these compounds to inhibit competitors in their environment.
Bacterial sources: Streptomyces and Bacillus genera
Fungal sources: Penicillium and Cephalosporium genera
By inhibiting other microbes, antibiotic producers reduce competition for nutrients and space.
Visual Example: Microbial Competition
The provided image shows a petri dish with various microbial colonies, illustrating the diversity of microbes and the potential for natural antibiotic production as a means of competition.
Additional info:
Antibiotics: Substances produced by microorganisms that inhibit or destroy other microbes.
Semi-synthetic drugs: Natural antibiotics modified in the laboratory to enhance their properties.
Synthetic drugs: Compounds synthesized entirely through chemical processes.
