Neomycin drug molecule. Ball-and-stick molecular model of neomycin, a broad-spectrum aminoglycoside antibiotic effective against both Gram-positive and Gram-negative bacteria. It is produced naturally by the actinomycete bacterium Streptomyces fradiae. It is found in many topical medications such as creams, ointments and eye drops. Its chemical formula is C23H46N6O13. Atoms are represented as spheres with colour coding: hydrogen (white), carbon (black), oxygen (red), and nitrogen (also black).