History of antimicrobial chemotherapy: Who proposed the foundational concept of ‘‘selective (specific) toxicity’’—the idea that a drug can target a pathogen more than the host?

Introduction / Context:
Selective toxicity underpins modern antimicrobial therapy: exploit biological differences between microbes and humans to achieve efficacy with minimal harm. Identifying its origin highlights how conceptual breakthroughs shape clinical practice.

Given Data / Assumptions:

• We are asked for the scientist associated with specific toxicity.
• Multiple historical figures made pivotal contributions to microbiology and antibiotics.
• Only one coined and advanced this specific principle in chemotherapy.

Concept / Approach:
Paul Ehrlich articulated ‘‘selective toxicity’’ and pursued ‘‘magic bullets’’ that would selectively kill pathogens. His work on arsphenamine (Salvarsan) for syphilis inaugurated systematic antimicrobial chemotherapy. Fleming discovered penicillin; Pasteur pioneered germ theory and vaccination; Watson is associated with DNA structure; Lister with antisepsis.

Step-by-Step Solution:
Match the concept to the correct historical figure.Exclude contemporaries whose contributions lie elsewhere (antisepsis, vaccines, discovery rather than conceptual chemotherapy).Select ‘‘Paul Ehrlich’’.

Verification / Alternative check:
Ehrlich’s work established screening paradigms for antimicrobial activity, a practice continued in modern drug discovery.

Why Other Options Are Wrong:
They are important pioneers but did not originate the selective toxicity framework.

Common Pitfalls:
Attributing selective toxicity to Fleming due to penicillin’s fame; the concept predates antibiotic era.

Final Answer:
Paul Ehrlich.