Antibacterial agent 200 (pyridyl HH 7), a unique hydrazyl hydroxycoumarin (HH), has strong antibacterial efficacy and broad antibacterial spectrum with MIC values ranging from 0.5 to 32 μg/mL for Gram-positive and Gram-negative bacteria. Antibacterial agent 200 exhibits a good inhibition against Pseudomonas aeruginosa 27853 with a low MIC value of 0.5 μg/mL. Antibacterial agent 200 can eradicate the integrity of bacterial membrane, result in the leakage of intracellular proteins, and interact with bacterial DNA gyrase via non-covalent binding^[1].