Unveiling the Emergence and Genetic Diversity of OXA-48-like Carbapenemase Variants in Shewanella xiamenensis .

An increase in the carbapenem-hydrolyzing capacity of class D β -lactamase has been observed in strains of multiple species, posing a significant challenge to the control of antibiotic resistance. In this study, we aimed to investigate the genetic diversity and phylogenetic characteristics of new bla OXA-48 -like variants derived from Shewanella xiamenensis . Three ertapenem-non-susceptible S. xiamenensis strains were identified, one isolated from the blood sample of an inpatient, the other two isolated from the aquatic environment. Phenotypic characterization confirmed that the strains were carbapenemase producers and exhibited antimicrobial resistance patterns to ertapenem, with some showing lower susceptibility to imipenem, chloramphenicol, ciprofloxacin, and tetracycline. No significant resistance to cephalosporins was observed. Sequence analysis revealed that one strain harbored bla OXA-181 and the other two strains harbored bla OXA-48 -like genes, with open reading frame (ORF) similarities with bla OXA-48 ranging from 98.49% to 99.62%. The two novel bla OXA-48 -like genes, named bla OXA-1038 and bla OXA-1039 , respectively, were cloned and expressed in E. coli . The three OXA-48-like enzymes demonstrated significant hydrolysis activity against meropenem, and the classical β -lactamase inhibitor had no significant inhibitory effect. In conclusion, this study demonstrated the diversity of the bla OXA gene and highlighted the emergence of novel OXA carbapenemases in S. xiamenensis . Further attention to S. xiamenensis and OXA carbapenemases is recommended for the effective prevention and control of antibiotic-resistant bacteria.