Gentamicin, an aminoglycoside antibiotic, is isolated from Micromonospora purpurea, a genus of Gram-positive bacteria. It consists of a mixture of three isomers, gentamicin C1, gentamicin C1a and gentamicin C2. Gentamicin interacts with the 30S subunit of prokaryotic ribosomes, and then it inhibits bacterial growth by inhibiting protein synthesis. Gentamicin has activity against mostly Gram-negative bacteria including Pseudomonas, Proteus, Serratia, and the Gram-positive Staphylococcus. But, it is not used for Pneumococcus, Hemolytic streptococci, Bacteroides, Rickettsia and fungus. Gentamicin is widely used because of its potent bactericidal activities and less bacterial resistance, but it is well known to cause nephrotoxicity and hypacusis.