Biochemical and genetic characterization of the action of triclosan on Staphylococcus aureus

Abstract

Triclosan, a widely used antibacterial agent, possesses potent activity against Staphylococcus aureus. This study reports on an investigation of the antibacterial target of triclosan in this pathogen. A strain of S. aureus overexpressing the enoyl-[acyl-carrier-protein] reductase (FabI), demonstrated by Western immunoblotting, gave rise to an increase in the MIC of triclosan, while susceptibilities to a range of unrelated antibacterials were unaffected. There are approximately 12 000 molecules of FabI per cell in mid-log phase growth. This number increased by approximately three- to four-fold in the S. aureus FabI overexpressor. Triclosan selectively inhibited the incorporation of [(14)C]acetate into TCA-precipitable product, an indicator of fatty acid biosynthesis. Furthermore, it inhibited de novo fatty acid biosynthesis in this organism. In vitro, triclosan inhibited recombinant, purified S. aureus FabI with an IC(50) of approximately 1 microM. The combination of these biochemical and genetic data provide further evidence that the mode of action of triclosan in S. aureus is via inhibition of FabI.

A genome‐wide strategy for the identification of essential genes in Staphylococcus aureus

“…7). In contrast, the same cells were not significantly sensitized to a variety of antibiotics that inhibit different protein targets, for example, targets involved in the synthesis of DNA, RNA, proteins, cell wall synthesis or even to triclosan (Slater-Radosti et al, 2001), an inhibitor of another fatty acid synthesis enzyme, enoyl-ACP reductase. All strongly inhibitory antisense clones to known antibiotic targets that we have tested show hypersensitivity to their respective antibiotics (data not shown).…”

Antistaphylococcal Activity of CG400549, a New Experimental FabI Inhibitor, Compared with That of Other Agents

“…In S. aureus and Escherichia coli, this enzyme has been shown to be the antibacterial target of triclosan and diazaborines, thereby showing the essentiality of FabI in these organisms (17,20). FabI is absent in some organisms, and an alternative enoyl-ACP reductase, FabK, is present in some pathogens, such as Streptococcus pneumoniae.…”

Reduced Triclosan Susceptibility in Methicillin-Resistant Staphylococcus epidermidis

“…This finding has led to recent concern about the ability of microbes to become resistant to triclosan through both target-based (8,14) and efflux-based (5, 6) mechanisms.…”