Prevalence, Development, and Molecular Mechanisms of Bacteriocin Resistance inCampylobacter
ABSTRACTBacteriocins (BCNs) are antimicrobial peptides produced by bacteria with narrow or broad spectra of antimicrobial activity. Recently, several unique anti-CampylobacterBCNs have been identified from commensal bacteria isolated from chicken intestines. These BCNs dramatically reducedC. jejunicolonization in poultry and are being directed toward on-farm control ofCampylobacter. However, no information concerning prevalence, development, and mechanisms of BCN resistance inCampylobacterexists. In this study, susceptibilities of 137C. jejuniisolates and 20C. coliisolates to the anti-CampylobacterBCNs OR-7 and E-760 were examined. Only oneC. colistrain displayed resistance to the BCNs (MIC, 64 μg/ml), while others were susceptible, with MICs ranging from 0.25 to 4 μg/ml. TheC. colimutants resistant to BCN OR-7 also were obtained byin vitroselection, but all displayed only low-level resistance to OR-7 (MIC, 8 to 16 μg/ml). The acquired BCN resistance inC. colicould be transferred at intra- and interspecies levels amongCampylobacterstrains by biphasic natural transformation. Genomic examination of the OR-7-resistant mutants by using DNA microarray and random transposon mutagenesis revealed that the multidrug efflux pump CmeABC contributes to both intrinsic resistance and acquired resistance to the BCNs. Altogether, this study represents the first report of and a major step forward in understanding BCN resistance inCampylobacter, which will facilitate the development of effective BCN-based strategies to reduce theCampylobacterloads in poultry.