Use of lipids to potentiate the antibacterial activity of aminoglycosides.

Linolenyl alcohol has been shown to inhibit the in vitro growth of several species of gram-positive bacteria. Since the double bonds in linolenyl alcohol could undergo autooxidation, the antimicrobial activities of saturated primary alcohols of similar molecular sizes against Streptococcus mutans BHT were evaluated. Tridecan-1-ol was identified as the most active compound, eliciting a bacteriostatic effect at concentrations at which growth occurred in the presence of other saturated alcohols or linolenyl alcohol. Evidence is also presented that the combined use of tridecan-1-ol and gentamicin sulfate produces a synergistic effect that is bactericidal to S. mutans BHT. A similar bactericidal response was observed when tridecan-1-ol was combined with other aminoglycosides or tested alone against other strains of S. mutans.

Effect of linolenyl alcohol on the in-vitro growth of the oral bacterium Streptococcus mutans.

The effect of primary aliphatic alcohols of varying chain length and degree of unsaturation on bacterial growth was assessed, using Strep. mutans BHT as the main test organism. Unsaturated alcohols, linoleyl and linolenyl, effectively inhibited bacterial growth. Of the saturated alcohols, only lauryl and myristyl alcohols inhibited the growth of Strep. mutans BHT, but at concentrations much higher than those required for the unsaturated alcohols. All Gram-positive organisms tested were sensitive to linolenyl alcohol. Gram-negative bacteria did not exhibit the sensitivity. Linoleic and linolenic acid were inactive as antibacterial agents at the same concentration as the related alcohol. Repeated exposure of Strep. mutans BHT to linolenyl alcohol produced no change in the sensitivity of the organism to the alcohol. Significant amounts of linolenyl alcohol were found in bacteria grown in the presence of this lipid for 24 h but linolenic acid was not detected. Thus the primary polyunsaturated aliphatic alcohols, particularly linolenyl alcohol, could be effective antibacterial agents for the prevention of dental caries and periodontal disease.