Sisomicin drug molecule. Ball-and-stick molecular model of sisomicin, an aminoglycoside antibiotic. It is a newer broad-spectrum aminoglycoside antibiotic, most structurally similar to gentamicin. Of the aminoglycoside antibiotics, sisomicin has the greatest activity against Gram-positive bacteria. Its chemical formula is C19H37N5O7. Atoms are represented as spheres with conventional colour coding: hydrogen (white), carbon (black), oxygen (red), and nitrogen (blue).