Purpose: This study was conducted to investigate the effect of citric extracts in the activity of AI-2 molecules that mediated QS in Campylobacter jejuni and their influence on motility and biofilm formation.
Methods: Cultures of Campylobacter jejuni were exposed to citric extracts (lemon peel, cider peel and orange peel) at different concentrations. For swarm motility test, sub-inhibitory concentrations of plant extracts were mixed with Muller Hinton with 0.3% agar. 5 µl of a C. jejuni culture were placed in the center of the plate and incubated for 48 h in microaerophilic conditions. The extent of swarming motility was determined by measuring the diameter of migration and compared with control. Biofilm formation in polyestirene microtiter plates with brucella broth was quantified after staining with safranin at O.D. 495 nm in a microplate reader. AI-2 activity was determined from supernatants of C. jejuni cultures in brucella broth; these were added into fresh culture (AB medium) of V.harveyi BB170. Culture supernatants of V. harveyi BB152 were used as positive control. The luminescence values were measured with a VictorX2 multilabel reader luminometer.
Results: Swarm motility was reduced 50% when treated with lemon peel or cider peel extract, and 35 to 40% for orange extract. Citric extracts reduced biofilm formation by 60 to 75% depending on extract concentration and /or strain tested. The AI-2 activity in supernatants treated with citric extracts decreased in most cases at levels of 90% Relative Light Units (RLU)
Significance : This study provides an insight of the effect of natural edible antimicrobials on QS and virulence factors of Campylobacter jejuni.