Netilmicin Pathway

Netilmicin is a semisynthetic, water soluble antibiotic of the aminoglycoside group, produced by the fermentation of Micromonospora inyoensis, a species of actinomycete. Netilmicin binds irreversibly to the bacterial 30S ribosomal subunit protein and 16S rRNA and prevents the formation of the initiation complex with messenger RNA. More specifically, netilmicin binds four nucleotides of the 16S rRNA and a single amino acid of protein S12. This interferes with the decoding site in the vicinity of nucleotide 1400 in 16S rRNA of the 30S subunit. This region interacts with the wobble base of the anticodon of tRNA. This leads to interference with the initiation complex, misreading of mRNA so that incorrect amino acids are inserted into the polypeptide leading to nonfunctional or toxic peptides, and the breakup of polysomes into nonfunctional monosomes.

Aminoglycosides are useful primarily in infections involving aerobic, Gram-negative bacteria, such as Pseudomonas, Acinetobacter, and Enterobacter. It is active at low concentrations against a wide variety of pathogenic bacteria including Escherichia coli, bacteria of the Klebsiella-Enterobacter-Serratia group, Citrobacter sp., Proteus sp. (indole-positive and indole-negative), including Proteus mirabilis, P. morganii, P. rettgrei, P. vulgaris, Pseudomonas aeruginosa and Neisseria gonorrhoea. Netilmicin is also active in vitro against isolates of Hemophilus influenzae, Salmonella sp., Shigella sp. and against penicillinase and non-penicillinase-producing Staphylococcus including methicillin-resistant strains. Some strains of Providencia sp., Acinetobacter sp. and Aeromonas sp. are also sensitive to netilmicin. Many strains of the above organisms which are found to be resistant to other aminoglycosides, such as kanamycin, gentamicin, tobramycin and sisomicin, are susceptible to netilmicin in vitro. Occasionally, strains have been identified which are resistant to amikacin but susceptible to netilmicin. The combination of netilmicin and penicillin G has a synergistic bactericidal effect against most strains of Streptococcus faecalis (enterococcus). The combined effect of netilmicin and carbenicillin or ticarcillin is synergistic for many strains of Pseudomonas aeruginosa. In addition, many isolates of Serratia, which are resistant to multiple antibiotics, are inhibited by synergistic combinations of netilmicin with carbenicillin, azlocillin, mezlocillin, cefamandole, cefotaxime or moxalactam. Aminoglycosides are mostly ineffective against anaerobic bacteria, fungi and viruses.