The antibiofilm effect of shikimic acid in Pseudomonas aeruginosa by interfering the algD gene

Chlorogenic acid (CA), a principal bioactive constituent prevalent in numerous Chinese herbal medicines, exhibits well-documented antibacterial efficacy. However, CA is rapidly metabolized into its metabolites in the intestine and liver, yet their specific mechanisms against Pseudomonas aeruginosa (P. aeruginosa) biofilms remain unclear. This study demonstrated that shikimic acid, a key metabolite of CA, effectively inhibits biofilm formation in clinical P. aeruginosa strains without impeding bacterial growth. This antibiofilm activity was linked to the significant suppression of extracellular polymeric substance (EPS) and alginate production, as well as the impairment of bacterial motility. By integrating transcriptome analysis with RT-PCR validation, it is postulated that the antibiofilm action of shikimic acid may be attributed to its regulatory effects on the constituents of the EPS within the biofilm, especially extracellular polysaccharides. Moreover, shikimic acid predominantly downregulated genes associated with alginate synthesis, among which algD exhibited the most significant expression alteration.