Controlling Microbial Growth in the Body: Antimicrobial Drugs

Controlling Microbial Growth in the Body: Antimicrobial Drugs

Introduction

This chapter explores the history, development, and mechanisms of antimicrobial drugs, which are essential tools in controlling microbial growth and treating infectious diseases. Understanding the origins and actions of these agents is fundamental in microbiology and clinical practice.

History of Antimicrobial Agents

Definitions and Key Terms

• Drugs: Chemicals that affect physiology in any manner.

• Chemotherapeutic agents: Drugs that act against diseases.

• Antimicrobial agents (antimicrobials): Drugs that treat infections by inhibiting or killing microorganisms.

Major Historical Figures and Discoveries

• Paul Ehrlich: Proposed the concept of "magic bullets"—chemicals that selectively target pathogens. Developed arsenic compounds effective against microbes.

• Alexander Fleming: Discovered penicillin, the first true antibiotic, released from the mold Penicillium.

• Gerhard Domagk: Discovered sulfanilamide, the first widely used synthetic antimicrobial.

• Selman Waksman: Discovered antibiotics produced naturally by organisms, such as streptomycin from Streptomyces species.

Example: Antibiotic Effect of Penicillium chrysogenum

When Penicillium chrysogenum is cultured with Staphylococcus aureus, a clear zone forms around the mold where bacterial growth is inhibited. This demonstrates the antibiotic effect of penicillin.

Types of Antimicrobial Agents

• Semi-synthetics: Chemically altered antibiotics that are more effective, longer lasting, or easier to administer than naturally occurring ones.

• Synthetics: Antimicrobials that are completely synthesized in the laboratory, not derived from natural sources.

Table: Sources of Some Common Antibiotics and Semisynthetics

Antibiotic/Semisynthetic	Source Organism
Penicillin	Penicillium chrysogenum (fungus)
Streptomycin	Streptomyces griseus (bacterium)
Cephalosporins	Acremonium (fungus)
Vancomycin	Amycolatopsis orientalis (bacterium)
Additional info:	This table summarizes the natural sources of several important antibiotics and their semisynthetic derivatives.

Why Aren't Antibiotics Effective Against the Common Cold?

• The common cold is caused by viruses, not bacteria.

• Antibiotics target bacterial structures or functions and are ineffective against viral pathogens.