Resveratrol against Arcobacter butzleri and Arcobacter cryaerophilus: Activity and effect on cellular functions

The frequent isolation of Arcobacter butzleri and Arcobacter cryaerophilus from food samples makes it imperative to search for potential compounds able to inhibit the development of these bacteria. Taking this into consideration, this study focuses on the antimicrobial activity of resveratrol and its mechanism of action against A. butzleri and A. cryaerophilus. The activity of resveratrol was assessed by a microdilution method and time-kill curves. Resveratrol effect on cellular functions was assessed by flow cytometry evaluating intracellular DNA content and metabolic activity. Ethidium bromide (EtBr) accumulation in the presence of resveratrol was also evaluated, as well as the susceptibility to resveratrol in the presence of phenylalanine-arginine beta-naphthylamide (PA beta N). Scanning electron microscopy (SEM) was used to further evaluate cell damage caused by resveratrol. Resveratrol presented MIC values of 100 and 50 mu g/mL to A. butzleri and A. cryaerophilus, respectively. Based on the time-kill curves, resveratrol exhibited bactericidal activity, leading to a >= 3 log(10) CFU/mL reduction of initial inoculums, for A. butzleri exponential phase cells incubated for 6 h with 1 x MIC or with 2 x MIC after 24 h for stationary phase cells. For A. cryaerophilus cells in exponential growth phase, 99.9% killing was achieved after 24 h incubation with 2 x MIC, whereas, for stationary phase cells, bactericidal activity was only detected after incubation with 4 x MIC. Incubation with resveratrol led to a decrease in both intracellular DNA content and metabolic activity. An increase in the accumulation of EtBr was observed in the presence of resveratrol, and the efflux pump inhibitor PAM reduced the MIC of resveratrol. SEM analysis revealed disintegration of A. butzleri cells treated with resveratrol, whereas no morphological alteration was observed for A. cryaerophilus cells. Resveratrol has a good anti-Arcobacter activity, and the results obtained suggest that this compound could act through several different mechanisms in the inhibition of this microorganism. The results encourage the use of this compound for the development of potential strategies to control Arcobacter in food products. (C) 2014 Elsevier B.V. All rights reserved.