Design a set of three desirable chemical or pharmacologic properties you would prioritize when synthesizing a new broad-spectrum antibiotic intended to penetrate both Gram-positive and Gram-negative bacteria; which combination below best supports broad spectrum activity?

• A. Very large molecular size to avoid efflux pumps, extreme hydrophobicity preventing solubility, and a highly variable target found in only a subset of bacteria to avoid resistance development.
• B. A drug design focused solely on inhibiting peptidoglycan in species with unique cell walls, with no consideration for porin passage or conserved intracellular targets across Gram classes.
• C. Molecular features that prevent any membrane interaction so the drug remains extracellular, exclusive binding to eukaryotic kinases to potentiate immune responses, and rapid renal clearance to limit toxicity.
• D. Small molecular size compatible with porin passage, moderate hydrophilicity to traverse porins plus sufficient lipophilicity to cross inner membranes, and a target located in the cytoplasm that is conserved across diverse bacteria.

Answer: (D)