The fexA gene in Campylobacter: whether the spread has occurred among various hosts in eastern China.

Objectives: The emergence of the florfenicol resistance gene fexA in Campylobacter poses a serious threat to public health, but the extent of the spread of fexA in Campylobacter from various hosts has not been well understood. This study aimed to investigate the fexA in Campylobacter isolates from different hosts.

Methods: PCR was used to identify fexA-positive Campylobacter from different hosts during 2008-2019 in China, and the fexA-positive isolates were characterized by susceptibility tests, whole-genome sequencing, and natural transformation.

Results: A total of 69 (2.54%, 69/2721) fexA-positive Campylobacter were identified, and the fexA-positive isolates increased remarkably (0.42%-16.90%) since it was first detected in 2010. By source, the 69 isolates were obtained from chickens (3.57%, 57/1595), geese (3.43%, 7/204), ducks (1.02%, 2/197), and environments (2.86%, 3/105); the fexA-positive isolates were not isolated in humans and pigs. In addition to fexA, these isolates also carried other antimicrobial resistance genes and exhibited multidrug resistance. Whole-genome sequencing analysis showed the fexA gene can disseminate clonally or horizontally via either multidrug resistance genomic islands or insertion sequences among the Campylobacter. The genetic structure IS1216-∆ISEfa11-hp-fexA-NAD(P)H-∆ISEfa11-IS1216 was conserved and widespread in the Campylobacter of various origins, and the IS1216 can form fexA-carrying circular intermediates, emphasizing that IS1216 plays an important role in the spread of fexA in Campylobacter.

Conclusions: This study indicates the wide spread of fexA-positive Campylobacter in poultry and environments. Because multidrug resistance genomic islands and IS1216 can facilitate the transmission of fexA, systematic surveillance should be implemented to prevent the spread of fexA to humans.