Co-Occurrence of an NDM-1-Carrying SGI1 Variant and a Novel GIflu-1 Resistance Island in a Seafood-Derived Vibrio fluvialis

Vibrio fluvialis is an important zoonotic pathogen that poses a growing threat to both public health and aquaculture, particularly to shrimp and fish farming. In this study, we report that a seafood-associated V. fluvialis strain, 10M-VF, possesses two genomic islands, SGI1-VfNDM1 and GIflu-1, in addition to hemolysins and type VI secretion systems (T6SSs). SGI1-VfNDM1 is a new member of the Salmonella genomic island 1 (SGI1) and harbors several antibiotic resistance genes. A potential transferable region, ISCR1-trpF-bleMBL-blaNDM-1, was observed in SGI1-VfNDM1, suggesting that ISCR1 may have mediated the integration of blaNDM-1 into this island. Additionally, GIflu-1 represents a novel resistance island. Other GIflu variants carrying resistance genes in Vibrio all possess ISCR2, but their resistance regions vary. This indicates that ISCR2 may contribute to the integration of antibiotic resistance genes into GIflu islands. Notably, not every GIflu variant carries drug resistance genes. To the best of our knowledge, GIflu-1 is a previously unreported resistance island, and no previous report has documented the co-existence of two distinct resistance genomic islands in a single Vibrio isolate. The emergence of such resistance islands in a seafood-borne pathogen raises concerns for the maintenance and potential dissemination of clinically important resistance genes in aquatic food systems and underscores the need for ongoing surveillance of resistance determinants in seafood-borne Vibrio populations from a One Health perspective.