Inhibitors of bacterial cell wall ( β-lactams, vancomycin) enhance entry of aminoglycosides and exhibit synergism. Penetration is also favoured by high pH aminoglycosides are ~20 times more active in alkaline than inĪcidic medium. These processes are inactivated under anaerobic conditions anaerobes are not sensitive and facultativeĪnaerobes are more resistant when O 2 supply is deficient, e.g. Thus, penetration is dependent upon maintenance of a polarized membrane and on oxygen dependent active processes (energyĭependent phase I or EDP 1 entry). Entry from the periplasmic space across the cytoplasmic membrane is carrier mediated which is linked to the electron transport chain. They diffuse across the outer coat of gram-negative bacteria through porin channels. Transport of aminoglycoside into the bacterial cell is a multistep process. (b) Binding to ribosomes resulting in inhibition of protein synthesis. (a) Transport of the aminoglycoside through the bacterial cell wall and cytoplasmic membrane. The aminoglycosides are bactericidal antibiotics, all having the same general pattern of action which may be described in two main steps: All exhibit ototoxicity and nephrotoxicity. They have relatively narrow margin of safety.ĩ. There is only partial cross resistance among them.Ĩ. All are active primarily against aerobic gram-negative bacilli and do not inhibit anaerobes.ħ. They act by interfering with bacterial protein synthesis.Ħ. All are bactericidal and more active at alkaline pH.ĥ. All are excreted unchanged in urine by glomerular filtration.Ĥ. They ionize in solution are not absorbed orally distribute only extracellularly do not penetrate brain or CSF.ģ. All are used as sulfate salts, which are highly water soluble solutions are stable for months.Ģ. All aminoglycosides are produced by soil actinomycetes and have many common properties ( see box).Ĭommon properties of aminoglycoside antibioticsġ. Others were produced later, and now aminoglycosides are a sizable family. It assumed great importance because it was active against tubercle bacilli.
Streptomycin was the first member discovered in 1944 by Waksman and his colleagues. Unlike penicillin, which was a chance discovery, aminoglycosides are products of deliberate search for drugs effective against gram-negative bacteria. These are a group of natural and semisynthetic antibiotics having polybasic amino groups linked glycosidically to two or more aminosugar (streptidine, 2-deoxy streptamine, garosamine) residues. Selected References for Further Reading.Drugs Acting on Skin and Mucous Membranes Drugs for Peptic Ulcer and Gastroesophageal Reflux Disease Drugs Used in Mental Illness: Antipsychotic and Antimanic Drugs Androgens and Drugs for Erectile Dysfunction 5-Hydroxytryptamine, its Antagonists and Drug Therapy of Migraine
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