Development and inter-laboratory validation of analytical methods for glufosinate and its two metabolites in foods of plant origin.

Glufosinate is widely used to control various weeds. Glufosinate and its main metabolites have become the focus of attention because of their high water solubility and persistence in aquatic systems. Quantification of the agrochemical product and its metabolite residues is essential for the safety of agricultural products. In this study, a highly specific, simple method was developed to directly determine glufosinate and its metabolite residues in 21 plant origin foods by liquid chromatography with tandem mass spectrometry (LC-MS/MS), and it was validated on 11 foods in five laboratories. Finally, the repeatability limit, reproducibility limit, and uncertainty of the method were calculated based on these validated data and used to support the more accurate detection results. Four different chromatographic columns were used to analyze three target compounds, and the anionic polar pesticide column showed the optimum separation and peak shape. Composition of the mobile phase, extraction solvent, and the clean-up procedure were optimized. The developed method was validated on 21 plant origin foods. The average recoveries were 74-115% for all matrices. The validation results of five laboratories showed this method had a good repeatability (RSDr < 9.5%) and reproducibility (RSDR < 18.9%). The method validation parameters met the requirements of guidance established by the European Union (EU) and China for pesticide residue analysis. This methodology can be used for a routine monitoring that performs well for glufosinate and its metabolite residues.

Preparative isolation of the major metabolite NK-1375 of diamide insecticide cyclaniliprole and its application to pertinent residue analysis in plant-origin foods using UHPLC-MS/MS.

NK-1375 is a major metabolite of the diamide insecticide cyclaniliprole (CYCP) with toxicological significance. It is formed in various transformation pathways of CYCP, including photolysis and plant metabolism. In the present study, NK-1375 was produced employing the liquid-phase photolysis of CYCP followed by isolation using preparative liquid chromatography. The structure of the isolated substance was confirmed using MS and 1 H NMR spectroscopy, and its purity was measured to be 95.9% using HPLC. As its application, a residue analysis method was first developed for the simultaneous determination of CYCP and NK-1375 in six representative plant-origin foods using fast multi-plug filtration cleanup and UHPLC-MS/MS. Excellent linearity (r > 0.999) was obtained over the calibration range from 0.001 to 0.1 µg mL-1 . The recoveries (intra-day and inter-day) of CYCP and NK-1375 from different matrices ranged from 74 to 112%, with corresponding relative standard deviations less than 13%. The limits of quantitation of these two compounds were defined at 0.01 mg kg-1 . This study can be useful for the subsequent analytical or toxicological research on this important pesticide metabolite.

Urinary tract infection and sepsis causing potential of multidrug-resistant Extraintestinal pathogenic E. coli isolated from plant-origin foods.

The dissemination of Extraintestinal pathogenic Escherichia coli (ExPEC) in food is a critical concern for human health and food safety. The present study is the first to systematically examine the diverse plant-origin foods such as cucumber, carrot, tomato, radish, chilli, fenugreek, coriander, peppermint, spring onion, cabbage, and spinach for the presence of ExPEC or specific putative ExPEC pathotypes with an in-depth assessment of their phylogenetics, virulence, and drug resistance. A total of 77 (15.9 %) ExPEC isolates were recovered from 1780 samples of the diverse plant-origin foods of distinct environments. Specific putative ExPEC pathotypes such as Uropathogenic E. coli (UPEC, 23.3 %) and Septicemia-associated E. coli (SEPEC, 24.6 %) were identified among ExPEC isolates. The Clermont revisited new phylotyping method revealed the varied distribution (1-27 %) of specific putative ExPEC pathotypes in the different phylogenetic lineages such as A, D/E, B1, and Clade 1, etc. All putative ExPEC pathotypes possess multiple genes (4.3-92.8 %) or phenotypes (3.3-100 %) associated with their virulence. In-vitro antimicrobial susceptibility testing of all putative ExPEC pathotypes demonstrated the presence of 100 % multidrug resistance with moderate to high (52-100 %) resistance to drugs used as last-resorts (chloramphenicol, colistin) or frontline (nitrofurantoin, sulfamethoxazole, ampicillin, gentamicin) in ExPEC-associated infections in humans. Overall, the present findings significantly contribute to our better understanding of the presence of ExPEC in the non-clinical niche, such as plant-origin foods with a possible consequence on human health and food safety.

Characterization of Cronobacter sakazakii Strains Originating from Plant-Origin Foods Using Comparative Genomic Analyses and Zebrafish Infectivity Studies.

Cronobacter sakazakii continues to be isolated from ready-to-eat fresh and frozen produce, flours, dairy powders, cereals, nuts, and spices, in addition to the conventional sources of powdered infant formulae (PIF) and PIF production environments. To understand the sequence diversity, phylogenetic relationship, and virulence of C. sakazakii originating from plant-origin foods, comparative molecular and genomic analyses, and zebrafish infection (ZI) studies were applied to 88 strains. Whole genome sequences of the strains were generated for detailed bioinformatic analysis. PCR analysis showed that all strains possessed a pESA3-like virulence plasmid similar to reference C. sakazakii clinical strain BAA-894. Core genome analysis confirmed a shared genomic backbone with other C. sakazakii strains from food, clinical and environmental strains. Emerging nucleotide diversity in these plant-origin strains was highlighted using single nucleotide polymorphic alleles in 2000 core genes. DNA hybridization analyses using a pan-genomic microarray showed that these strains clustered according to sequence types (STs) identified by multi-locus sequence typing (MLST). PHASTER analysis identified 185 intact prophage gene clusters encompassing 22 different prophages, including three intact Cronobacter prophages: ENT47670, ENT39118, and phiES15. AMRFinderPlus analysis identified the CSA family class C ß-lactamase gene in all strains and a plasmid-borne mcr-9.1 gene was identified in three strains. ZI studies showed that some plant-origin C. sakazakii display virulence comparable to clinical strains. Finding virulent plant-origin C. sakazakii possessing significant genomic features of clinically relevant STs suggests that these foods can serve as potential transmission vehicles and supports widening the scope of continued surveillance for this important foodborne pathogen.

Biogenic Amines in Plant-Origin Foods: Are They Frequently Underestimated in Low-Histamine Diets?

Low-histamine diets are currently used to reduce symptoms of histamine intolerance, a disorder in histamine homeostasis that increases plasma levels, mainly due to reduced diamine-oxidase (DAO) activity. These diets exclude foods, many of them of plant origin, which patients associate with the onset of the symptomatology. This study aimed to review the existing data on histamine and other biogenic amine contents in nonfermented plant-origin foods, as well as on their origin and evolution during the storage or culinary process. The only plant-origin products with significant levels of histamine were eggplant, spinach, tomato, and avocado, each showing a great variability in content. Putrescine has been found in practically all plant-origin foods, probably due to its physiological origin. The high contents of putrescine in certain products could also be related to the triggering of the symptomatology by enzymatic competition with histamine. Additionally, high spermidine contents found in some foods should also be taken into account in these diets, because it can also be metabolized by DAO, albeit with a lower affinity. It is recommended to consume plant-origin foods that are boiled or are of maximum freshness to reduce biogenic amine intake.