We evaluated extracts from Alpinia katsumadai seeds for anti-Campylobacter activity and confirmed the roles of the CmeABC and CmeDEF efflux pumps in Campylobacter resistance to these natural phenolics. Additionally, we confirmed resistance-modifying activities of A. katsumadai extracts as putative efflux pump inhibitors on Campylobacter isolates and mutants in efflux pump genes. Thus we demonstrate the potential use of A. katsumadai extracts for the control of Campylobacter and its antimicrobial resistance in the food industry.
The increasing prevalence of intestinal bacteria Campylobacter and their increased antibiotic resistance is most likely due to the use of antibiotics in animal production. This is only in recent years restricted or prohibited, so natural phenolic compounds of plant origin can be further developed for potential use in controlling Campylobacter. Multiple mechanisms associated with antibiotic resistance have been identified in Campylobacter spp., while the mechanism involved in the resistance to phenolics is not known. Using mutants that lack the functional genes coding for the CmeB and CmeF efflux pump proteins and the CmeR transcriptional repressor; and EPIs, we demonstrated that complex efflux mechanisms are involved in the resistance of C. jejuni to phenolic compounds and extracts of plant phenolics. Particularly, the CmeABC efflux pump is a significant player in reducing the susceptibility to the phenolics, while CmeDEF plays a modest role in the resistance. Additionally, our results suggest that non-CmeABC and non-CmeDEF efflux systems also contribute to Campylobacter resistance to phenolic compounds. These findings represent the first comprehensive evaluation of the anti-Campylobacter activities of natural phenolics and suggest that alternative compounds can be further developed to control Campylobacter contamination in food production and processing, or as therapeutics for clinical treatment of campylobacteriosis.