Whole-genome sequencing of strains of Vibrio spp. from China reveals different genetic contexts of blaCTX-M-14 among diverse lineages.

OBJECTIVES

To investigate the prevalence and genetic contexts of the blaCTX-M-14 gene harboured by foodborne isolates of Vibrio spp. in China.

METHODS

A total of 1856 Vibrio spp. isolates collected from raw meat and shrimp samples in Guangdong Province of China were screened for blaCTX-M-14 by PCR. The blaCTX-M-14-positive isolates were characterized by MIC, PFGE, MLST, conjugation, S1-PFGE and Southern blotting and WGS using Illumina and Nanopore platforms.

RESULTS

A total of 35 (1.9%) Vibrio isolates were positive for blaCTX-M-14, including 33 Vibrio parahaemolyticus strains and two Vibrio alginolyticus strains. MLST showed that most of the blaCTX-M-14-bearing isolates could be assigned into two major STs, with ST163 being more prevalent (n = 23), followed by ST180 (n = 6). Whole-genome analysis of these 35 isolates revealed that the blaCTX-M-14 gene was associated with ISEcp1 in the upstream region, of which 32 blaCTX-M-14 genes were located in the same loci of chromosome I, 1 blaCTX-M-14 gene was located in a novel chromosomal integrative conjugative element (ICE) belonging to the SXT/R391 family and 2 blaCTX-M-14 genes were located in the same type of plasmid, which belonged to the IncP-1 group. Conjugation experiments showed that only the plasmid-borne blaCTX-M-14 gene could be transferred to the recipient strain Escherichia coli J53.

CONCLUSIONS

The emergence of the novel ICE and IncP-1 plasmids has contributed to the variable genetic contexts of blaCTX-M-14 among strains of Vibrio spp. and facilitated the horizontal transfer of such genes between Vibrio spp. and other zoonotic pathogens, resulting in a rapid increase in the prevalence of blaCTX-M-14-bearing bacterial pathogens worldwide.