Identification of a Novel Genomic Island Conferring Resistance to Multiple Aminoglycoside Antibiotics in Campylobacter coli

Abstract

ABSTRACTHistorically, the incidence of gentamicin resistance inCampylobacterhas been very low, but recent studies reported a high prevalence of gentamicin-resistantCampylobacterisolated from food-producing animals in China. The reason for the high prevalence was unknown and was addressed in this study. PCR screening identified aminoglycoside resistance genesaphA-3andaphA-7and theaadE–sat4–aphA-3cluster among 41Campylobacterisolates from broiler chickens. Importantly, a novel genomic island carrying multiple aminoglycoside resistance genes was identified in 26 aminoglycoside resistantCampylobacter colistrains. Sequence analysis revealed that the genomic island was inserted betweencadFandCOO1582on theC. colichromosome and consists of 14 open reading frames (ORFs), including 6 genes (theaadE–sat4–aphA-3cluster,aacA-aphD,aac, andaadE) encoding aminoglycoside-modifying enzymes. Analysis by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing indicated that theC. coliisolates carrying this unique genomic island were clonal, and the clone of PFGE subtype III and sequence type (ST) 1625 was particularly predominant among theC. coliisolates examined, suggesting that clonal expansion may be involved in dissemination of this resistance island. Additionally, we were able to transfer this genomic island fromC. colito aCampylobacter jejunistrain using natural transformation under laboratory conditions, and the transfer resulted in a drastic increase in aminoglycoside resistance in the recipient strain. These findings identify a previously undescribed genomic island that confers resistance to multiple aminoglycoside antibiotics. Since aminoglycoside antibiotics are used for treating occasional systemic infections caused byCampylobacter, the emergence and spread of this antibiotic resistance genomic island represent a potential concern for public health.