Antimicrobial chemotherapy — origin of the concept of selective toxicity Who first articulated the principle of selective toxicity (the idea that a drug can harm pathogens more than the host), leading to the search for “magic bullets”?

Introduction / Context:
Selective toxicity is a cornerstone of antimicrobial chemotherapy: agents should target microbial structures or pathways that are absent or sufficiently different in the host. This concept launched systematic searches for specific antimicrobials and underpins modern drug design and safety assessment.

Given Data / Assumptions:

• The question concerns early 20th-century pharmacology and microbiology.
• We distinguish idea originators from later discoverers of specific antibiotics.
• “Magic bullet” refers to Ehrlich’s metaphor for selectively targeting pathogens.

Concept / Approach:
Paul Ehrlich proposed selective toxicity, developed the first effective anti-syphilis drug (Salvarsan), and popularized the “magic bullet” idea. Others made seminal contributions—Fleming discovered penicillin serendipitously; Pasteur advanced germ theory and vaccination; Leeuwenhoek first observed microbes; Domagk developed sulfonamides—but Ehrlich defined the principle asked here.

Step-by-Step Solution:
Identify the conceptual origin of selective toxicity.Associate “magic bullet” with Paul Ehrlich.Eliminate contributors whose primary achievements were different in scope or timing.

Verification / Alternative check:
Textbook histories of chemotherapy consistently credit Ehrlich for formulating selective toxicity and pioneering targeted antimicrobial therapy.

Why Other Options Are Wrong:

• A: Leeuwenhoek discovered microscopic life but did not propose selective toxicity.
• C: Pasteur laid crucial groundwork for germ theory, not chemotherapy selectivity.
• D: Fleming discovered penicillin later; he did not originate the principle.
• E: Domagk’s sulfa drug work came after Ehrlich’s concept.

Common Pitfalls:
Conflating the first discovery of an antibiotic with the earlier conceptual framework defining how antimicrobial drugs should work.

Final Answer:
Paul Ehrlich