Abstract
Due to health concerns associated with the increase of antimicrobial resistance in foodborne pathogens such as Salmonella, plant extracts have become important natural alternatives to known antimicrobials. The eradication effect of the water-soluble stinging nettle extracts with 2 mg/mL, 4 mg/mL, 6 mg/mL, 8 mg/mL, 12 mg/mL, 16 mg/mL, and 20 mg/mL concentrations, on pre-formed biofilms and swimming motility of Salmonella enterica subspecies enterica serovars, including Newport, Typhimurium, Enteritidis, Virchow, Othmarschen and Mikawasima, was investigated in vitro. Degradation of biofilm formation on spinach inoculated with each serovar was ascertained within different exposure time of 40 mg/mL concentrated extract as well. Moreover, major genes responsible for biofilm formation (i.e., rpoS, mlrA, ycfR, fimA, spiA and csgA) were screened in these isolates. The extract significantly decreased swimming motilities of Mikawasima and Virchow serovars. The highest reductions were found as 0.88 Log CFU/mL and 2.00 Log CFU/cm2 in vitro and on spinach, respectively.