Disc diffusion tests were used to evaluate antibacterial activity. Wild-type E. coli (R477), the LpxC inhibitor hypersensitive E. coli R477 (LpxC G17S), and wild-type P. aeruginosa (PAO1) were tested for killing by L-161,240, CHIR-090, tobramycin, and ciprofloxacin. Each disc contained 20 μg of compound dissolved in DMSO.