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.