Suppressive actions of inorganic ions on the bioactivity of aminoglycoside antibiotics.

Many independent studies have shown that inorganic salts can suppress the inhibitory activities of aminoglycoside antibiotics against various bacterial species. From studies on the nature and mechanism of this suppressive ion effect, several conclusions can be drawn. Both monovalent and divalent cation salts can inhibit aminoglycoside action. At least two different mechanisms are apparently involved. The first is divalent cation dependent and has been described with $\text{Pseudomonas aeruginosa}$ and $\text{Mycobacterium smegmatis}$. With $\text{M. smegmatis}$, the effect aappears to be dependent more on a double positive charge than on particular metal ion species. The second mechanism is related to ionic strength and is elicited by both monovalent and divalent cation salts against many different organisms. However, based on studies with $\text{M. smegmatis}$, it appears that each of the two mechanisms involves interferance with the initial instantaneous electrostatic binding of drug at the cell surface.