tobramycin

noun

to·​bra·​my·​cin ˌtō-brə-ˈmīs-ᵊn 

: a colorless water-soluble antibiotic C₁₈H₃₇N₅O₉ isolated from a soil bacterium of the genus Streptomyces (S. tenebrarius) and effective especially against gram-negative bacteria

Note: When used in combination with loteprednol to treat inflammatory conditions of the eye, tobramycin is marketed under the trademark Zylet.