blaOXA -731 , a new chromosome-encoded blaOXA -48 -like variant in Shewanella sp. from the aquatic environment in Myanmar.

Shewanella sp., the progenitors of blaOXA-48 -like genes are increasingly reported with the possession of different blaOXA-48 -like variants. This study aims to characterize blaOXA-731 , a new variant of a blaOXA-48 -like gene identified in Shewanella sp. isolated from the aquatic environment in Myanmar. Phylogenetic analysis of the blaOXA-731 sequence with other blaOXA-48 -like variants showed that it has the highest nucleotide identity of 86.09% with blaOXA-48 . However, the active site motifs in OXA-731 were 100% identical to that in OXA-48. Whole-genome sequencing analysis showed that blaOXA-731 is not surrounded by any mobile genetic elements. The genetic context of blaOXA-731 was found as similar to other blaOXA-48 -like genes previously identified in Shewanella sp. S1 nuclease pulsed-field gel electrophoresis followed by Southern blotting confirmed the location of blaOXA-731 in the chromosome of the Shewanella genome. Cloning and expression studies showed that OXA-731 has β-lactamase activity similar to OXA-48 and OXA-181, but it has no significant carbapenemase activity. Our results showed the significance of blaOXA-48 -like-carrying Shewanella sp. in the spreading of blaOXA-48 -like genes in the community.