Arsenic bioaccumulation in ready-to-eat oysters can contribute to the selection of WHO critical priority enterobacterales displaying a virulent behavior

Abstract

The bioaccumulation of arsenic (As) in shellfish poses a serious threat to human health, whereas the occurrence of antimicrobial-resistant bacteria in seafood raises food safety concerns. We investigated the occurrence and genomic background of WHO critical-priority Enterobacterales in ready-to-eat (RTE) oysters, and their association with As bioaccumulation. RTE oysters collected between September 2022 and March 2023, in five Brazilian markets, were analyzed. In brief, oyster tissue samples were aseptically removed and processed for isolation and identification of carbapenem- and/or third-generation cephalosporin-resistant Enterobacterales, using MALDI-TOF (Bruker) and disk diffusion methods. Heavy metal tolerance was evaluated by microdilution assays. Quantification of As, Hg, Cu, Co, Ag and Pb was performed by inductively coupled plasma optical emission spectrometry and atomic absorption spectrometry. Enterobacterales were sequenced by Illumina NextSeq, and virulence was evaluated using the Galleria mellonella infection model. Statistical analysis was made with Phyton. Total As concentrations in RTE oysters ranged from 0.44 to 1.95 mg/kg. Five As-tolerant (MIC≥1024 μg/mL) and multidrug-resistant Enterobacterales producing extended-spectrum beta-lactamases (ESBLs) were identified. WGS confirmed the ars operon among international clones of Klebsiella pneumoniae (ST307) coproducing CTX-M-15 and SHV-28, Escherichia coli (ST38 and ST23) producing CTX-M-15 and CTX-M-55, and K. quasipneumoniae (ST526) producing SHV-5 ESBLs. Citrobacter telavivensis producing CTX-M-15 in seafood is reported for the first time. E. coli ST38 and ST23 exhibited highly virulent behavior and phylogenomic relationships with human lineages. The occurrence of WHO priority pathogens and As bioaccumulation in oysters is a public health issue that requires surveillance and appropriate management strategies.