Triclosan inhibition of fatty acid synthesis and its effect on growth of Escherichia coli and Pseudomonas aeruginosa

Objectives: To assess the effect of triclosan on fatty acid synthesis and to relate the inhibition of enoyl reductase to bacterial viability. Methods: The effect of triclosan on fatty acid synthesis in a triclosan-resistant Escherichia coli and its sensitive counterpart and in Pseudomonas aeruginosa was investigated by measuring acetate incorporation into total lipid followed by analysis of fatty acid methyl esters by gas chromatography. Concurrently, the bactericidal effect of triclosan against these bacterial strains was assessed. Results: Triclosan inhibited fatty acid biosynthesis in all the strains tested. However, for triclosan-resistant E. coli (MIC > 1000mg/L) the concentration required to achieve inhibition was higher than that required for the susceptible counterpart. These concentrations did not significantly affect cell survival in any of the strains tested. Conclusions: This study shows that the inhibition of fatty acid biosynthesis by the bisphenol might be involved in its growth-inhibitory action and that other mechanisms are involved in its lethal effect. In addition, although microorganisms with a high triclosan MIC were still susceptible to the inhibitory effect of the bisphenol on fatty acid biosynthesis, a higher concentration of the compound was required. This suggested that triclosan bioavailability was different in these strains.