Neomycin

Neomycin is a common antibiotic which belongs the aminoglycoside group of antibiotics. It is found in many topical medications such as ointments, eyedrops, and cream. Neomycin is a broad spectrum antibiotic effective against both gram positive and gram negative bacteria, interfering with protein synthesis in sensitive bacterial cells such as species of Proteus and Staphylococcus.

Neomycin is commonly used as a topical preparation like Neosporin. It can be given orally, too, but 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.

Neomycin was discovered by the microbiologist Selman Waksman and his student Hubert Lechevalier at Rutgers University in 1949. It is produced naturally by the bacterium Streptomyces fradiae.

Aminoglycosides

An aminoglycoside is a molecule composed of a sugar group and an amino group. Several aminoglycosides function as antibiotics that are effective against certain types of bacteria. They include amikacin, arbekacin, gentamicin, kanamycin, neomycin, netilmicin, paromomycin, rhodostreptomycin, streptomycin, tobramycin, and apramycin. Anthracyclines are another group of aminoglycosides. These compounds are used in chemotherapy.

Aminoglycosides are potent bactericidal antibiotics that act by creating fissures in the outer membrane of the bacterial cell. They are particularly active against aerobic, gram-negative bacteria and act synergistically against certain gram-positive organisms. Amikacin may be particularly effective against resistant organisms. Aminoglycosides that are derived from bacteria of the Streptomyces genus are named with the suffix -mycin, while those which are derived from Micromonospora are named with the suffix -micin.

Aminoglycosides are used in the treatment of severe infections of the abdomen and urinary tract, as well as bacteremia and endocarditis. They are also used for prophylaxis, especially against endocarditis. Resistance is rare but increasing in frequency. Avoiding prolonged use, volume depletion and concomitant administration of other potentially nephrotoxic agents decreases the risk of toxicity.

The first aminoglycoside, streptomycin, was isolated from Streptomyces griseus in 1943. Neomycin, isolated from Streptomyces fradiae, had better activity than streptomycin against aerobic gram-negative bacilli but, because of its formidable toxicity, could not safely be used systemically. Gentamicin, isolated from Micromonospora in 1963, was a breakthrough in the treatment of gram-negative bacillary infections, including those caused by Pseudomonas aeruginosa. Other aminoglycosides were subsequently developed, including amikacin (Amikin), netilmicin (Netromycin) and tobramycin (Nebcin), which are all currently available for systemic use in the United States.