Cellular and molecular responses of Salmonella Typhimurium to antimicrobial-induced stresses during the planktonic-to-biofilm transition.

AIM

To characterize the cellular and molecular properties of Salmonella Typhimurium exposed to antimicrobials in association with physicochemical property, biofilm formation ability and gene expression patterns.

METHODS AND RESULTS

The antimicrobial susceptibilities against Salmonella Typhimurium were evaluated to determine the MICs of allyl isothiocyanate (AITC), thymol, eugenol and polyphenol. Cell surface hydrophobicity, aggregation and biofilm formation assays were conducted to assess the physicochemical properties of Salm. Typhimurium treated with sublethal concentrations (SLC(2D) ) of antimicrobials. The expression patterns of adhesion-related genes (adrA, csgD, fimA and lpfE), virulence-related genes (hilA and stn) and efflux-related genes (acrA, acrB, ompD and tolC) were evaluated by real-time RT-PCR. Thymol exhibited the highest antimicrobial activity against Salm. Typhimurium planktonic, biofilm and dispersed cells, showing 0·18, 0·96 and 0·42 mg ml(-1) of SLC(2D) values, respectively. The antimicrobial-treated Salm. Typhimurium showed low hydrophobicity. The highest auto-aggregation ability (67%) of polyphenol-treated Salm. Typhimurium was positively associated with the enhanced ability to form biofilms. The csgD, fimA, hilA and lpfE genes were up-regulated in the polyphenol-treated Salm. Typhimurium planktonic and biofilm cells.

CONCLUSION

The results suggest that the antimicrobial resistance and virulence potential varied depending on the physiological states of Salm. Typhimurium during the transition from planktonic to biofilm cell growth.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study can expand our understanding of cellular and molecular mechanisms of biofilm formation and also provide useful information for reducing biofilm-associated virulence potential.