Identification and characterization of a conjugative bla_VIM-1-bearing plasmid in Vibrio alginolyticus of food origin

Objectives: To investigate the genetic features of the bla_VIM-1 gene first detected in a cephalosporin-resistant Vibrio alginolyticus isolate, Vb1978. 

Methods: The MICs of strain Vb1978 were determined, and the β-lactamases produced were screened and analysed using conjugation, S1-PFGE and Southern blotting. The complete sequence of the bla_VIM-1-encoding plasmid was also obtained using the Illumina and MinION sequencing platforms. 

Results: V. alginolyticus strain Vb1978, isolated from a retail shrimp sample, was resistant to cephalosporins and exhibited reduced susceptibility to carbapenems. A novel bla_VIM-1-carrying conjugative plasmid, designated pVb1978, was identified in this strain. Plasmid pVb1978 had 50 001 bp and comprised 59 predicted coding sequences (CDSs). The plasmid backbone of pVb1978 was homologous to those of IncP-type plasmids, while its replication region was structurally similar to non-IncP plasmids. The bla_VIM-1 gene was found to be carried by the class 1 integron In70 and associated with a defective Tn402-like transposon. 

Conclusions: A novel bla_VIM-1-carrying conjugative plasmid, pVb1978, was reported for the first time in V. alginolyticus, which warrants further investigation in view of its potential pathogenicity towards humans and widespread occurrence in the environment.