Neomycin is overwhelmingly used as a topical preparation. It can also be given orally, where it is usually combined with other antibiotics. Neomycin is not absorbed from the gastrointestinal tract, and has been used as a preventative measure for hepatic encephalopathy and hypercholesterolemia. By killing bacteria in the intestinal tract, it keeps ammonia levels low and prevents hepatic encephalopathy, especially prior to GI surgery. It has also been used to treat small intestinal bacterial overgrowth. It is not given intravenously, as neomycin is extremely nephrotoxic (causes kidney damage), especially compared to other aminoglycosides. The exception to this, is when it is included in some vaccines as a preservative, but in very small quantities -typically 0.025 mg per dose[1].
Molecular Biology
Neomycin resistance is conferred by either one of two aminoglycoside phosphotransferase genes[2]. A neo gene is commonly included in DNA plasmids used by molecular biologists to establish stable mammalian cell lines expressing cloned proteins in culture; many commercially available protein expression plasmids contain neo as a selectable marker. Non-transfected cells will eventually die off when the culture is treated with neomycin or similar antibiotic. For practical reasons, geneticin (G418) rather than neomycin is generally used when making stable cell lines.
Spectrum
Similar to other aminoglycosides, neomycin has excellent activity against Gram negative bacteria, and has partial activity against Gram positive bacteria. It is relatively toxic to humans, and many people have allergic reactions to it.[1] See: Hypersensitivity. Physicians sometimes recommend using antibiotic ointments without neomycin, such as Polysporin.citation needed
History
Neomycin was discovered in 1949 by the microbiologist Selman Waksman and his student Hubert Lechevalier. It is produced naturally by the bacterium Streptomyces fradiae.
