Genetic Environment Surrounding in Clinical Isolates of Shewanella algae Clade and Enhanced Expression of in a Carbapenem-Resistant Isolate.

Although spp. are most frequently isolated from marine environments; more rarely, they have been implicated in human infections. spp. are also recognized as the origin of genes for carbapenem-hydrolyzing class D β-lactamases. Due to the spread globally among in recent years, risk assessments of both clinical and environmental strains are urgently needed. In this study, we analyzed the whole-genome sequences of 10 clinical isolates and 13 environmental isolates of spp. and compared them with those of species strains registered in public databases. In addition, the levels of transcription and β-lactamase activity of a carbapenem-resistant Shewanella algae isolate were compared with those of carbapenem-susceptible S. algae clade isolates. All clinical isolates were genetically identified as S. algae clade (S. algae, Shewanella chilikensis, and Shewanella carassii), whereas all but one of the environmental isolates were identified as various spp. outside the S. algae clade. Although all isolates of the S. algae clade commonly possessed an approximately 12,500-bp genetic region harboring , genetic structures outside this region were different among species. Among S. algae clade isolates, only one showed carbapenem resistance, and this isolate showed a high level of transcription and β-lactamase activity. Although this study documented the importance of the S. algae clade in human infections and the relationship between enhanced production of OXA-55-like and resistance to carbapenems in S. algae, further studies are needed to elucidate the generalizability of these findings. spp., which are known to carry chromosomally located genes, have mainly been isolated from marine environments; however, they can also cause infections in humans. In this study, we compared the molecular characteristics of clinical isolates of spp. with those originating from environmental sources. All 10 clinical isolates were genetically identified as members of the Shewanella algae clade (S. algae, , and ); however, all but one of the 13 environmental isolates were identified as species members outside the S. algae clade. Although all the S. algae clade isolates possessed an approximately 12,500-bp genetic region harboring , only one isolate showed carbapenem resistance. The carbapenem-resistant isolate showed a high level of transcription and β-lactamase activity compared with the carbapenem-susceptible isolates. To confirm the clinical significance and antimicrobial resistance mechanisms of the S. algae clade members, analysis involving more clinical isolates should be performed in the future.