Final answer:
Selective toxicity is a principle that guides the use of chemotherapeutic agents, ensuring they target pathogens effectively while minimizing harm to host cells.
Step-by-step explanation:
Selective toxicity refers to the ability of chemotherapeutic agents to specifically target and eliminate pathogens without causing harm to the host organism. A drug with a high degree of selective toxicity can interact with vital structures or enzymes unique to the microbial cells, thus killing the infectious agent or inhibiting its growth, with minimal or no damage to the host's cells. Characteristics such as whether a drug is bacteriostatic or bactericidal, its spectrum of activity, and potential side effects are crucial in determining the appropriateness of an antimicrobial drug for therapy.