title: Anti-Campylobacter activities and resistance mechanisms of natural phenolic compounds in Campylobacter.
abstract: BACKGROUND
  Campylobacter is a major foodborne pathogen and alternative antimicrobials are needed to prevent or decrease Campylobacter contamination in foods or food producing animals. The objectives of this study are to define the anti-Campylobacter activities of natural phenolic compounds of plant origin and to determine the roles of bacterial drug efflux systems in the resistance to these natural phenolics in Campylobacter jejuni.
  
  
  RESULTS
  Anti-Campylobacter activities were evaluated by an MIC assay using microdilution coupled with ATP measurement. Mutants of the cmeB and cmeF efflux genes and the cmeR transcriptional repressor gene were compared with the wild-type strain for their susceptibilities to phenolics in the absence and presence of efflux-pump inhibitors (EPIs). The phenolic compounds produced significant, but variable activities against both antibiotic-susceptible and antibiotic resistant Campylobacter. The highest anti-Campylobacter activity was seen with carnosic and rosmarinic acids in their pure forms or in enriched plant extracts. Inactivation of cmeB rendered C. jejuni significantly more susceptible to the phenolic compounds, while mutation of cmeF or cmeR only produced a moderate effect on the MICs. Consistent with the results from the efflux pump mutants, EPIs, especially phenylalanine-arginine β-naphthylamide and NMP, significantly reduced the MICs of the tested phenolic compounds. Further reduction of MICs by the EPIs was also observed in the cmeB and cmeF mutants, suggesting that other efflux systems are also involved in Campylobacter resistance to phenolic compounds.
  
  
  CONCLUSIONS
  Natural phenolic compounds of plant origin have good anti-Campylobacter activities and can be further developed for potential use in controlling Campylobacter. The drug efflux systems in Campylobacter contribute significantly to its resistance to the phenolics and EPIs potentiate the anti-Campylobacter activities of plant phenolic compounds.
authors.affiliation: Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Anja
authors.initials: A
authors.lastname: Klančnik
authors.forename: Sonja Smole
authors.initials: SS
authors.lastname: Možina
authors.forename: Qijing
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D045784:Abietanes / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002169:Campylobacter Infections / Q000188:drug therapy* / Q000382:microbiology; D016123:Campylobacter jejuni / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification; D002934:Cinnamates / Q000494:pharmacology; D053630:Depsides / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D010636:Phenols / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology*; D000097123:Rosmarinic Acid
chemical_list: D045784:Abietanes; D000900:Anti-Bacterial Agents; D000975:Antioxidants; D001426:Bacterial Proteins; D002934:Cinnamates; D053630:Depsides; D026901:Membrane Transport Proteins; D010636:Phenols; D010936:Plant Extracts; D000097123:Rosmarinic Acid; C018381:salvin