A novel chromosomally encoded OXA-12-like β-lactamase variant (bla OXA-1433 ) in a new Aeromonas veronii sequence type (ST3591) from ready-to-eat oysters
Year: 2026
Type: preprint
Abstract: Antibiotic resistance, a natural feature of bacterial evolution, is not confined to clinical settings but actively circulates across aquatic and terrestrial ecosystems, food chains, and animal and human populations. Aquatic ecosystems serve both as reservoirs of resistance determinants and as sources of food production, making seafood a critical interface for human exposure to environmentally derived resistance genes. This study aimed to characterize a novel chromosomally encoded OXA-12-like β-lactamase variant ( bla OXA−1433 ) identified in a new Aeromonas veronii sequence type (ST3591) isolated from ready-to-eat oysters, and to investigate its genetic, structural, and phenotypic features. The isolate was subjected to hybrid whole-genome sequencing using short- and long-read technologies, followed by genome assembly, multilocus sequence typing, genomic context characterization, and antimicrobial susceptibility testing. The novel bla OXA−1433 variant was further characterized through sequence and phenotypic analyses. MLST analysis revealed a novel sequence type (ST3591), while genome mining identified a previously undescribed OXA-12-like β-lactamase variant. OXA-1433 shared 95.08% amino acid identity with OXA-12 and differed by 13 amino acid substitutions while retaining the conserved motifs characteristic of class D β-lactamases. Genomic context analysis demonstrated that bla OXA−1433 was chromosomally located within a conserved genomic region lacking detectable mobile genetic elements. Phenotypic assays demonstrated imipenem hydrolysis, consistent with carbapenemase activity. The identification of a novel A. veronii sequence type carrying a previously undescribed OXA-12-like β-lactamase variant expands current knowledge of the genetic diversity of this species in food-associated environments and highlights the value of genomic surveillance of seafood-associated bacteria for monitoring the evolution of antibiotic resistance determinants.
Source: Research Square
Institutions: University of Lisbon, Universidade Federal de Santa Catarina
Language: English
Subfield: Molecular Medicine
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7224675349