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- MERSEL FISH: Development and validation of a new analytical approach for the simultaneous speciation analysis of mercury and selenium by HPLC ICP MSPublication . Mendes Ribeiro, Mariana; Leufroy, Axelle; Danion, Morgane; Castanheira, Isabel; Silva, José Armando; Jitaru, PetruMercury (Hg) is one of the most hazardous chemicals to the environment and the most worrisome contaminant for public health. This is due to its extreme toxicity, particularly in the methylated form which is biomagnified in the food chain, the main pathway of contamination of the humans. The great ability of CH3Hg+ to be bioaccumulated in the aquatic food chain leads to considerably elevated levels of Hg in aquatic organisms, despite nearly immeasurable quantities in the water column. No maximum level for CH3Hg+ is yet regulated by the European commission (EC) in fishery products, despite its extreme toxicity. This is most likely arising from the difficulty in performing accurate speciation analysis of CH3Hg+ in complex matrices such as fishery products. It is also interesting to note that mercury bio-availability seems to be linked to the selenium levels. Although it was shown for a few decades that selenium (Se) shows protective effects against Hg bioaccumulation and toxicity, the mechanism is very poorly understood nowadays. This work report the development and optimization of a new analytical approach for the simultaneous speciation analysis of mercury (Hg2+ and CH3Hg+) and selenium (SeIV, Se VI, SeMet and SeCys) in fish by HPLC-ICP-MS. This method will be employed further for the assessment of dietary exposure to Hg & Se species bio-accumulation by fish, for the analysis of cooked samples as well as for the in vitro simulated digestion studies, to achieve the main aim of this study which is a deep assessment of the Hg-Se interaction in fish and the human dietary exposure.
- Plasmid-Mediated Colistin Resistance (mcr-1) in Escherichia coli from Non-Imported Fresh Vegetables for Human Consumption in PortugalPublication . Manageiro, Vera; Jones-Dias, Daniela; Ferreira, Eugénia; Caniça, ManuelaIn this study, we report the presence of the plasmid-mediated colistin resistance (PMCR)-encoding gene mcr-1 in an Escherichiacoli isolate, INSali25, recovered from lettuce produced and marketed in Portugal. Colistin MIC from the vegetable E. coli isolate-determined by microdilution broth method according to EUCAST guidelines-revealed a non-wild-type phenotype of colistin (MIC 16 mg/L). To understand the genetic background of E. coli INSali25, we performed whole genome sequencing. Plasmid sequencing was also performed after plasmid DNA extraction from the transconjugant TcINSali25 (mcr-1). Directed bioinformatics analysis identified the mcr-1 gene in a 39,998 bp length contig, with an upstream region including the antibiotic resistance gene blaTEM-1 in a partial transposon Tn2, truncated by the insertion sequence IS26 and showing >99% identity with previously described mcr-1-harboring IncHI2 plasmids. Further in silico analysis showed the presence of additional genes conferring resistance to β-lactams (blaTEM-1), aminoglycosides (aadA1, aph(4)-Ia, aph(6)-Id, aac(3)-Iv), macrolides (mdf(A)-type), phenicol (floR-type), tetracycline (tetA), and sulphonamides (sul2). INSali25 isolate belonged to the ST1716 lineage and showed the fimH54 and fumC27 alleles. Lettuce is a vegetable that is commonly consumed fresh and not subjected to any cooking process, which may amplify human food safety risks. Moreover, the occurrence of plasmid-mediated colistin resistance in a sample that was not imported and was acquired in a large retail store reinforces the widespread distribution of mcr-1.