Abstract: Lactic acid bacteria (LAB) with inhibitory activity against quorum sensing of Aeromonas hydrophila were screened from traditional fermented vegetables using the filter paper method. The biofilm inhibitory activity of the LAB isolates was measured by a 96-well microtiter plate reader, and their effect on the biofilm formation of A. hydrophila was observed by light microscopy and scanning electron microscopy (SEM). The proteolytic activity, siderophore production, swarming and swimming were used as indicators to evaluate the effects of these quorum sensing inhibitors (QSI) on the virulence of A. hydrophila. In this study, a strain designated SCT-2, with inhibitory activity toward quorum sensing of A. hydrophila, was isolated from pickled cabbage from Jinzhou, Liaoning province. Crude metabolite extract from strain SCT-2 at 8 mg/mL inhibited the biofilm formation of A. hydrophila by 45.16%. Light microscopy revealed that the crude extract pronouncedly inhibited the biofilm formation of A. hydrophila. The SEM images also revealed that the crude extract not only decreased the production of biofilm of A. hydrophila, but also destroyed the biofilm. The secretion amount of proteolytic and siderophore in A. hydrophila treated with 8 mg/mL of the crude extract was decreased by 27.18% and 22.11%, respectively. In addition, the crude extraction degraded 32.27% of the N-acylhomoserine lactones (AHLs) of A. hydrophila. It also inhibited obviously the swarming and swimming of A. hydrophila. Strain SCT-2 was identified as Lactobacillus plantarum by physiological and biochemical tests and 16S rRNA sequence analysis. This study may pave the foundation for the development LAB-based biological agent for inhibiting quorum sensing of A. hydrophila.

Key words: traditional fermented pickle, lactic acid bacteria, quorum sensing inhibitor, Aeromonas hydrophila, biofilm