MECHANISM OF ACTION

Aminoglycoside entry can be enhanced by cell wall synthesis inhibitors, which may be the basis of antimicrobial synergism. Susceptible gram-negative organisms allow aminoglycosides to diffuse through porin channels in their outer membranes. These organisms also have an oxygen-dependent system that transports the drug across the cytoplasmic membrane. The antibiotic then binds to the 30S ribosomal subunit prior to ribosome formation There, it interferes with assembly of the functional ribosomal apparatus and/or can cause the 30S subunit of the completed ribosome to misread the genetic code. Polysomes become depleted because the aminoglycosides interrupt the process of polysome disaggregation and assembly inibit translocation Aminoglycosides may also disrupt polysomal structure, resulting in nonfunctional monosomes.