Emergence of Multidrug-Resistant Campylobacter Species Isolates with a Horizontally Acquired rRNA Methylase

Abstract

ABSTRACTAntibiotic-resistantCampylobacterconstitutes a serious threat to public health, and resistance to macrolides is of particular concern, as this class of antibiotics is the drug of choice for clinical therapy of campylobacteriosis. Very recently, a horizontally transferrable macrolide resistance mediated by the rRNA methylase geneerm(B) was reported in aCampylobacter coliisolate, but little is known about the dissemination oferm(B) amongCampylobacterisolates and the association oferm(B)-carrying isolates with clinical disease. To address this question and facilitate the control of antibiotic-resistantCampylobacter, we determined the distribution oferm(B) in 1,554C. coliandCampylobacter jejuniisolates derived from food-producing animals and clinically confirmed human diarrheal cases. The results revealed that 58 of the examined isolates harborederm(B) and exhibited high-level resistance to macrolides, and most were recent isolates, derived in 2011-2012. In addition, theerm(B)-positive isolates were all resistant to fluoroquinolones, another clinically important antibiotic used for treating campylobacteriosis. Theerm(B) gene is found to be associated with chromosomal multidrug resistance genomic islands (MDRGIs) of Gram-positive origin or with plasmids of various sizes. All MDRGIs were transferrable to macrolide-susceptibleC. jejuniby natural transformation under laboratory conditions. Molecular typing of theerm(B)-carrying isolates by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) identified diverse genotypes and outbreak-associated diarrheal isolates. Molecular typing also suggested zoonotic transmission oferm(B)-positiveCampylobacter. These findings reveal an emerging and alarming trend of dissemination oferm(B) and MDRGIs inCampylobacterand underscore the need for heightened efforts to control their further spread.