Distinct dynamics of Vibrio parahaemolyticus populations in two farming models.

AIMS: Despite the recent prosperity of shrimp cultivation in China, very little is known about how different shrimp farming models influence the dynamics of Vibrio parahaemolyticus populations and the antibiotic resistance of this bacterium. METHODS AND RESULTS: To this end, we conducted continuous surveillance of V. parahaemolyticus on four farms over 3 years: two traditional shrimp farms with daily water exchange and two farms operated in the recirculating aquaculture systems (RAS). No antibiotics were used in these farms to exclude the potential impacts of antibiotics on the emergence of antibacterial resistance. Multilocus sequence typing was utilized to characterize the dynamics of V. parahaemolyticus populations. Whole-genome sequencing (WGS) was conducted to determine the representative sequence types (STs) at each farm. Results revealed that the population structure of V. parahaemolyticus remained stable over time in both RAS farms, with only nine and four STs observed at each. In contrast, annual replacement of V. parahaemolyticus populations was observed in traditional farms with 26 and 28 STs identified in rearing water. WGS of 50 isolates divided them into five clusters, of which ST917a isolates harboured a genomic island that disrupted the gene recA. Pair-wised genomic comparison of isolates from the same STs showed that they were genetically related but belonged to different clones associated with geographical distribution. CONCLUSIONS: These results suggested that RAS presented a specific ecological niche by minimizing the water exchanges with the external environment. In contrast, traditional farming might pose a food safety issue by introducing new V. parahaemolyticus populations with antibiotic resistance genes. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results expose the potential food safety issue associated with conventional agriculture and should encourage the development of preventive strategies to reduce the emergence of resistant V. parahaemolyticus populations.

Effect of copper on the accumulation and elimination kinetics of fluoroquinolones in the zebrafish (Danio rerio).

Fluoroquinolones (FQs) have attracted wide concerns due to their pseudo-persistent and universal presence in natural water. Here we exposed zebrafish separately to two FQs (enrofloxacin (ENR) and ofloxacin (OFL)) in different copper (Cu) concentrations for 20 days (d) in a flow-through system, followed by a 11 d depuration period in clean water to investigate compound specific bioaccumulation and tissue distribution. Two FQs could accumulate in zebrafish, and the high concentration was observed in liver. Moreover, the levels of FQs in different treatment groups were higher than the corresponding control fish group. The uptake rates (k1), elimination rates (k2), BCF value, and half-lives (t1/2) of FQs ranged from 0.02 to 3.28 d-1, 0.01 to 0.97 d-1, 0.33 to 109.33, 9.90 to 69.31 d, respectively. With Cu exposure concentration's increasing, k1 values in three tissues (liver, skin and gill) obviously decreased. The exposure concentration affected the BCF value significantly, but didn't change their relative compositions in liver, gill, skin, and muscle after long time exposure. BCF values of ENR were always a little bit higher than those of OFL in almost all the tissues (liver, skin and gill) in the low Cu concentration treatments, whereas, in the high Cu concentration treatments the bioconcentration factors (BCF) values of ENR were lower than the values of OFL. The exposure of Cu played an important role in the FQs bioconcentration and BCF. These results are meaningful for improved understanding and prediction of the behavior and fate of metallic and antibiotics in aqueous environments.

PFCA uptake and translocation in dominant wheat species (Triticum aestivum L.).

The comparative uptake of four perfluorinated carboxylic acids (PFCAs) by wheat (Triticum aestivum L.) grown in nutrient solution was investigated. Wheat is the main food crop in northern China and may become a potential pathway of human exposure to these PFCAs. The uptake of four PFCAs from water at a fixed concentration (1 µg/mL) increased over time, approaching a steady state, and except for the short-chain perfluorobutanoic acid, most of the total mass of each of the PFCAs taken up by wheat was found to be at the root. The root concentration factor (RCF) and shoot/root concentration factor (SRCF) were calculated, and with the increase in carbon chain length, the RCFs increased but SRCFs decreased, which indicated that long-chain PFCAs had stronger root uptake and weaker translocation capacities than short-chain PFCAs. In addition, pH could obviously impact the uptake of four PFCAs in the roots and shoots of wheat, and the highest concentrations were found at pH = 7 when the pH increased from 4 to 10.

Measurement of Temperature Dependence for Vapor Pressures of Seventeen OH-PBDEs and Eleven MeO-PBDEs by Gas Chromatographic Method.

Hydroxylated polybromodiphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) are emerging organic pollutants. Supercooled liquid vapor pressures (p L) and enthalpies of vaporization (∆vap H) for seventeen OH-PBDEs and eleven MeO-PBDEs were determined by a gas chromatographic technique. p L at 298 K ranged from 0.0173 Pa for 2'-OH-BDE3 to 2.32 × 10(-7) Pa for 3'-OH-BDE154 and they are approximately one order of magnitude smaller than those determined for the counterpart polybrominated diphenyl ethers (PBDEs). ∆vap H was in the range of 76-121 kJ/mol. The temperature dependence of p L was measured by fitting the experimental data with the log(p L/Pa) = a/(T/K) + b equation, and this corresponds to a 50-265 times higher p L value at 0 versus 30°C. Using fundamental quantum chemical descriptors, two quantitative structure-property relationship models (Q cum > 0.935) were developed to estimate p L at any temperature for the additional OH- and MeO-PBDE congeners.

Phototransformation of halobenzoquinones in aqueous solution under the simulate sunlight: Kinetics, mechanism and products.

Halobenzoquinones (HBQs) are a novel family of unregulated disinfection byproducts (DBPs). Little is known about their phototransformation activities in natural water. Here, five HBQs with various halogenated substituent types, numbers, and structures positions were selected to investigate the kinetics of degradation in aqueous solutions at various concentrations and in the presence of common environmental variables (Cl-, NO2-, and humic acid). The results indicated that dichloride and dibromo-substituted HBQs were photolyzed, whereas tetrachloro-substituted HBQs showed little degradation. The photolysis rate constant (k) of HBQs decreased with increasing initial concentration. The presence of NO2- and Cl- promoted the degradation of HBQs mainly through the formation of hydroxyl radical (•OH), which were confirmed by electron paramagnetic resonance (EPR). In contrast, humic acid played a negative role on HBQs transformation due to the adsorption and quenching reactions. Possible conversion pathways for HBQs were proposed based on the identification of two major photodegradation products, hydroxylated HBQs and halogenated-benzenetriol, as well as reactive free radicals. This study provided meaningful insights into the environmental fates and risk assessments of HBQs in natural aquatic system.

Citric acid can enhance the uptake and accumulation of organophosphate esters (OPEs) in Suaeda salsa rhizosphere: Potential for phytoremediation.

Bioaccumulation of organophosphate esters (OPEs) by plants has been widely studied, but how root exudates influence their bioavailability to plants is poorly understood. Here, we examined whether root exudates could promote desorption of OPEs, thereby enhancing bioavailability and subsequent accumulation potential. Root exudate components exert great influences on the sorption/desorption isotherms of OPEs in soils, resulting in activating OPEs and enhanced bioavailability. Among root exudate components, citric acid was confirmed to play a crucial role in driving OPEs, with 77.7-90.3 % attribution. Citric acid at rhizosphere levels (0.01-0.4 mM) can successfully reduce OPEs sorption to soils by decreasing electrostatic interaction, ligand exchange, and hydrophobic force. Pot experiments indicated that the addition of citric acid can significantly increase OPEs dissolution and bioaccumulation from the rhizosphere soil to Suaeda salsa. A higher level of citric acid in rhizosphere soil resulted in a higher accumulation of OPEs in Suaeda salsa, which was partly attributed to the enhanced OPEs mobility, and the increased root lengths (13.4-29.0 %) and tip numbers (60.2-120 %), promoting OPEs uptake by roots. Our findings suggest the activation process of OPEs in soils by citric acid at rhizosphere levels and provide insights into designing LMWOAs-enhanced phytoremediation techniques in natural environment.

The photoactivity of complexation of DOM and copper in aquatic system: Implication on the photodegradation of TBBPA.

The photoactivity of dissolved organic matter (DOM) has a great impact on the photodegradation of organic pollutants in natural waters. In this study, the photodegradation of TBBPA was investigated under simulated sunlight irradiation in the presence of copper ion (Cu2+), dissolved organic matter (DOM) and Cu-DOM complexation (Cu-DOM) to illustrate the effect of Cu2+ on photoactivity of DOM. The rate of photodegradation of TBBPA in the presence of Cu-DOM complex was 3.2 times higher than that in pure water. The effects of Cu2+, DOM and Cu-DOM on the photodegradation of TBBPA were highly pH dependent and hydroxyl radical(·OH) responded for the acceleration effect. Spectral and radical experiments indicated that Cu2+ had high affinity to fluorescence components of DOM, and acted as both the cation bridge and electron shuttle, resulting the aggregation of DOM and increasing of steady-state concentration of ·OH (·OHss). Simultaneously, Cu2+ also inhibited intramolecular energy transfer leading to the decrease of steady-state concentration singlet oxygen (1O2ss) and triplet of DOM (3DOM⁎ss). The interaction between Cu2+ and DOM followed the order of conjugated carbonyl CO, COO- or CO stretching in phenolic groups and carbohydrate or alcoholic CO groups. With these results, a comprehensive investigation on the photodegradation of TBBPA in the presence of Cu-DOM was conducted, and the effect of Cu2+ on the photoactivity of DOM was illustrated. These findings helped to understanding the potential mechanism of interaction among metal cation, DOM and organic pollutants in sunlit surface water, especially for the DOM-induced photodegradation of organic pollutants.

Levels, consumption, and variations of eight artificial sweeteners in the wastewater treatment plants of Dalian city, China.

Artificial sweeteners (ASs) are emerging contaminants in the environment, primarily derived from wastewater treatment plant (WWTP) effluents. In this study, the influents and effluents of three WWTPs in the Dalian urban area, China, were analyzed for the distribution of 8 typical ASs to investigate their seasonal fluctuations in the WWTPs. The results showed that acesulfame (ACE), sucralose (SUC), cyclamate (CYC), and saccharin (SAC) were both detected in the influent and effluent water samples of WWTPs, with concentrations ranging from not detected (ND) to 14.02 µg·L-1. In addition, SUC was the most abundant ASs type, accounting for 40 %-49 % and 78 %-96 % of the total ASs in the influent and effluent water, respectively. The WWTPs revealed high removal efficiencies of CYC, SAC, and ACE, while the SUC removal efficiency was poor (26 % ± 36 %). The ACE and SUC concentrations were higher in spring and summer, and all ASs showed lower levels in winter, which may be caused by the high consumption of ice-cream in warmer months. The per capita ASs loads in the WWTPs were determined in this study based on the wastewater analysis results. The calculated per capita daily mas loads for individual ASs ranged from 0.45 g·d-1·1000p-1 (ACE) to 2.04 g·d-1·1000p-1 (SUC). In addition, the relationship between per capita ASs consumption and socioeconomic status showed no significant correlation.

Photochemical reaction of glucocorticoids in aqueous solution: Influencing factors and photolysis products.

Glucocorticoids (GCs), as endocrine disruptors, have attracted widespread attention due to their impacts on organisms' growth, development, and reproduction. In the current study, the photodegradation of budesonide (BD) and clobetasol propionate (CP), as targeted GCs, was investigated including the effects of initial concentrations and typical environmental factors (Cl-, NO2-, Fe3+, and fulvic acid (FA)). The results showed that the degradation rate constants (k) were 0.0060 and 0.0039 min-1 for BD and CP at concentration of 50 µg·L-1, and increased with the initial concentrations. Under the addition of Cl-, NO2-, and Fe3+ to the GCs/water system, the photodegradation rate was decreased with increasing Cl-, NO2-, and Fe3+ concentrations, which were in contrast to the addition of FA. Electron resonance spectroscopy (EPR) analysis and the radical quenching experiments verified that GCs could transition to the triplet excited states of GCs (3GCs*) for direct photolysis under irradiation to undergo, while NO2-, Fe3+, and FA could generate ·OH to induce indirect photolysis. According to HPLC-Q-TOF MS analysis, the structures of the three photodegradation products of BD and CP were elucidated, respectively, and the phototransformation pathways were inferred based on the product structures. These findings help to grasp the fate of synthetic GCs in the environment and contribute to the understanding of their ecological risks.

Photoformation of environmentally persistent free radicals on particulate organic matter in aqueous solution: Role of anthracene and formation mechanism.

Environmentally persistent free radicals (EPFRs) generated under irradiation have been widely detected in soil particles, atmospheric particles and microplastic particles, but the formation of EPFRs in water is not well understood. This study investigated the formation of EPFRs on particulate organic matter (POM) in water contaminated by anthracene (Ant) under irradiation. The photoformation and decay progress of EPFRs was represented with the help of electron paramagnetic resonance (EPR) technique on both actual POM and Fe(III)-montmorillonite simulated samples. EPR signals at the range of 1016 to 1017 spin/g were detected and the half-life time of EPFRs stored in water was at around 16.62 h and 60.80 h, much shorter than those in the air. The g factors were all larger than 2.0040, which indicated the generation of oxygen centered EPFRs. The primary intermediates were identified by gas chromatography-mass spectrometer (GC-MS) and a possible EPFR formation pathway during Ant degradation was proposed. The interaction between Ant and POM, and the hydroxylation and carbonylation of the intermediates made contributions to the generation of EPFRs. Meanwhile, the indirect photodegradation of bisphenol A (BPA) has been demonstrated by analyzing the reactive oxygen species (ROS) and photogenerated electrons in the solution with POM containing EPFRs. It is found that hydroxyl radicals (•OH) and singlet oxygen (1O2) were induced and might promote the photodegration. Overall, our present study provided useful information to understand the photoformation of EPFRs on POM and their fate in aqueous environments.

Organophosphate esters (OPEs) in wetland soil and Suaeda salsa from intertidal Laizhou Bay, North China: Levels, distribution, and soil-plant transfer model.

Wetlands have attracted much attention due to releases of organophosphate esters (OPEs) and other emerging contaminants into this particular environment. Here, Suaeda salsa plants and wetland soils collected from Laizhou Bay, North China, were analyzed to investigate the levels, distribution, and soil-plant transfer of OPEs in these ecosystems. The Σ18OPEs concentrations ranged from 137 to 386 ng/g dry weight (dw), whereas in rhizosphere the concentrations were between 99.8 and 198 ng/g dw. Suaeda salsa rhizosphere could promote the absorption of OPEs in wetlands, and Suaeda salsa root presents a greater rate of absorption. The Σ18OPEs concentrations ranged from 32.9 to 56.8 ng/g dw in roots, 3.93 to 7.51 ng/g dw in stems, and 2.79 to 4.06 ng/g dw in leaves. Log RCFs, log TFr-s and log TFs-l showed no significant correlations with their log KOW, indicating the complexity of uptake and translocation in the natural environment. Predictive model for the OPEs availability to Suaeda salsa was established from the experimental data. The field-based BCFs of all OPEs were dependent on KOW, decreased with increasing KOW. This study provides important insights into the phytoremediation potential of OPEs using Suaeda salsa as an effective strategy and their role in environmental risk assessment of OPEs in wetlands.

One health pathogen surveillance demonstrated the dissemination of gut pathogens within the two coastal regions associated with intensive farming.

BACKGROUND: Intensive aquaculture farming has caused significant degradation of coastal wetlands and has been proposed as a reservoir for pathogenic Vibrio spp. RESULTS: Gut pathogens including Vibrio spp., Salmonella spp., and Klebsiella spp. were isolated from bird feces, shrimp and wetland water in two typical coastal regions of China in 2015 and 2017 and were subsequently subjected to whole-genome sequencing. Meanwhile, local patient isolates were also selected to confirm the epidemiological links. Bacterial community composition analyses of the sediments that were sampled in 2015 and 2017 were conducted by the hypervariable region 4 of the 16S rRNA gene. Together with the local clinical isolates, we observed highly related Vibrio isolates from waterbirds, wetlands and shrimp. Phylogenetic genome comparisons also demonstrated that sequence types ST3 and ST2414 Vibrio parahaemolyticus isolates obtained from aquatic animals were clonally related to patient isolates. Likewise, three Salmonella typhimurium isolates were also genomically related to one clinical strain. The results showed that farming activities significantly altered the community composition and resulted in the emergence of several pathogens, including Acinetobacter, Mycobacterium and Legionella. CONCLUSIONS: In conclusion, our results demonstrated that intensive shrimp farming in wetlands has two devastating impacts: pathogen dissemination from aquatic animals into migratory birds and transmission of foodborne pathogens into local communities.

Simultaneous determination of vanillin, ethyl vanillin and methyl vanillin in Chinese infant food and other dairy products by LC-MS/MS.

An efficient and simple method for determining vanillin, methyl vanillin and ethyl vanillin in milk and dairy products was developed using a liquid-liquid extraction (LLE) procedure coupled to high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Different extraction procedures were tested and optimised by spiking three vanillin compounds into a blank matrix in which none of any food additives were detected, and the extraction with acetonitrile solution and n-hexane as cleaning sorbent allowed an efficient recovery of 87.6-101.7% with RSDs less than 5%. The limit of detection (LOD) ranged from 6.2 to 20.1 µg/kg. High sensitivity, accuracy and selectivity were found for the in-house validated method, which can eliminate the interferences from complicated matrices effectively, and fulfil the quality criteria for routine laboratory application for real samples. The developed method was then finally applied to screen the three analytes in 65 milk and dairy products including infant formula milk powders from local markets to check for compliance with Chinese Regulation. Concentrations of the total vanillin and ethyl vanillin ranged from 0.0323 to 246.3 mg/kg, which is within the limits of Chinese regulations.

Continuous Genomic Surveillance Monitored the In Vivo Evolutionary Trajectories of Vibrio parahaemolyticus and Identified a New Virulent Genotype.

Our ability to predict evolutionary trajectories of pathogens is one of the promising leverages to fight against the pandemic disease, yet few studies have addressed this question in situ, due to the difficulty in monitoring the milestone evolutionary events for a given pathogen and in understanding the evolutionary strategies. In this study, we monitored the real-time evolution of Vibrio parahaemolyticus in response to successive antibiotic treatment in three shrimp farms in North China from 2011 to 2018 by whole-genome sequencing. Results showed that the stepwise emergence of resistance was associated with the antibiotic usage. Genomic analysis of resistant isolates showed that the acquisition of the resistant mobile genetic elements flanked by an insertion sequence (ISVal1) closely mirrored the antibiotics used in shrimp farms since 2014. Next, we also identified 50 insertion sites of ISVal1 in the chromosome, which facilitated the formation of pathogenicity islands (PAIs) and fitness islands in the following years. Further, horizontal transfers of a virulent trh-nik-ure genomic island (GI) and two GIs improving the fitness have been observed in two farms since 2016. In this case study, we proposed that the insertion sequence triggered four major evolutionary events during the outbreaks of shrimp disease in three farms, including horizontal transfer of transposon (HTT) (stage 1), the formation of resistance islands (stage 2) and the PAIs (stage 3), and horizontal transfer of the PAIs (stage 4). This study presented the first in vivo evolutionary trajectories for a given bacterial pathogen, which helps us to understand the emergence mechanisms of new genotypes.IMPORTANCE Most human infectious diseases originate from animals. Thus, how to reduce or prevent pandemic zoonoses before they emerge in people is becoming a critical issue. Continuous genomic surveillance of the evolutionary trajectories of potential human pathogens on farms is a promising strategy to realize early warning. Here, we conducted an 8-year surveillance of Vibrio parahaemolyticus in three shrimp farms. The results showed that the use of antibiotics and horizontal transfer of transposons (HTT) drove the evolution of V. parahaemolyticus, which could be divided into four stages: HTT, formation of resistance islands, formation of pathogenicity islands (PAIs), and horizontal transfer of PAIs. This study presented the first in vivo monitoring of evolutionary trajectories for a given bacterial pathogen, providing valuable information for the prevention of pandemic zoonoses.

Formation of free radicals by direct photolysis of halogenated phenols (HPs) and effects of DOM: A case study on monobromophenols.

The free radicals play an important role to understand direct/indirect transformation mechanisms of organic pollutants. However, very few efforts have been made to elucidate the radicals produced by direct photolysis. In this study, the short-lived radicals generated under simulated sunlight irradiation from representative halogenated phenols (HPs), monobromophenols, were investigated by electron paramagnetic resonance (EPR). The results showed that three radicals, carbon-centered radical (C), hydrogen radical (H) and hydroxyl radical (OH), were generated from the direct irradiation of HPs. Compared to other substitutions, halogenated atom at para-position led to the highest production of these radicals which is in accordance with the energies calculated by density functional theory. Based on the analyses of the reactive species and corresponding intermediate adducts, the possible reaction pathways for these radicals were tentatively proposed. Dissolved organic matters (DOM) could enhance the photodegradation of HPs by directly affecting the radicals' formation, mainly due to generation of excited triplet DOM (3DOM*). A positive correlation was found between the concentrations of hydrated electron and the steady state 3DOM* from different DOM. Our findings provided insights into environmental photochemical fate of HPs through their direct photolysis and will help more accurately understand their phototransformation mechanisms in the environment.

Photochemical reaction of tricresyl phosphate (TCP) in aqueous solution: Influencing factors and photolysis products.

Organophosphate triesters (OPEs) have caused great concern as a class of emerging environmental contaminants due to their widespread use and their toxicity to organisms. However, the phototransformation behavior of OPE is still not fully understood, which is important for understanding their environmental fate. In the present study, the photodegradation of tricresyl phosphate (TCP), one of the most widely detected OPEs in aqueous environments, was investigated including the direct photolysis and in the presence of several natural water factors, NO2-, Fe3+ and humic acid. The degradation process followed the pseudo-first-order kinetics, with rate constant increasing slightly with increasing initial TCP concentration. The presence of NO2- and Fe3+ was observed to promote the photochemical loss of TCP, while humic acid played a negative role on TCP transformation. Electron spin resonance (EPR) analysis showed that carbon-centered radical was produced in the photolysis process of TCP, and hydroxyl radical contributed to the promotion of rate constant for Fe3+ and NO2-. Four photolysis products were tentatively identified by HPLC-LTQ-Orbitrap MS analysis, and the possible degradation pathways of TCP were proposed. These findings provide a meaningful reference for the fate and transformation of OPEs in natural water.

Photoformation of persistent free radicals on a montmorillonite-humic acid complex simulated as particulate organic matter in an aqueous solution.

This study investigates the formation of persistent free radicals (PFRs) on particulate organic matter (POM) under irradiation in water. A montmorillonite-humic acid complex (Mnt-HA complex) was prepared to simulate POM, and the generated PFRs were detected by the electron paramagnetic resonance (EPR) technique. EPR signals with the trend of an initial increase and then a decrease were observed under irradiation for 8 days, and the g factors were in the range of 2.0034-2.0039, which indicated the generation of carbon-centered radicals with electrophilic moieties. Different concentrations and types of halophenols and transition-metal ions were respectively adsorbed on the Mnt-HA complex to probe their influence on the formation of PFRs. The amount of PFRs generated in the Mnt-HA complexes was in the order: 2-bromophenol (2-BP) > 2,4-dibromophenol (2,4-DBP) > 2,4-dichlorophenol (2,4-DCP), which implied that halogen substitution and the number of substituents in the halophenols could affect the generation of PFRs. The effects of transition-metal ions that resulted in the reduction of PFRs when adsorbed on the Mnt-HA complex were as follows: Fe3+ > Zn2+ > Cu2+ > Mn2+, and this is in agreement with their redox capacity. Analyzing the induced generation of reactive oxygen species (ROS) and electrons on POM, it is found that halophenols and transition metal ions also affected this process under irradiation. These findings indicate that the photoformation of PFRs on POM could be a source of PFRs in aqueous environments and requires further attention.

Adsorption behavior of azo dye C. I. acid red 14 in aqueous solution on surface soils.

Azo dyes have received considerable attention because of their association with various human health problems. The aim of the investigation is to determine the adsorption behavior of azo dyes in aqueous solution on DG06, GSE17200, and GSE17201 soils using C. I. Acid Red 14 (AR14) as example. The experimental results indicate that the Freundlich model expresses the adsorption isotherm better than the Langmuir model and the pseudo-second-order model achieves adsorption of AR14 on the three soils well. Based on the pseudo-second-order model, the adsorption thermodynamic of AR14 on DG06 soil have been studied and the thermodynamics parameter of deltaG0 is determined and deltaG0 value shows the adsorption process of AR14 on DG06 is mainly physical in nature. Furthermore, the effects of temperature, pH and salinity (NaCl) on adsorption have been investigated. The decrease in pH or the increase in salinity enhances the adsorption of AR14 by DG06, GSE17200, and GSE17201.

Occurrence and risk assessment of fluoroquinolones and tetracyclines in cultured fish from a coastal region of northern China.

Occurrence and levels of 11 fluoroquinolones (FQs) and four tetracyclines (TC) in 14 cultured fish species from a coastal city in the northern China were investigated. Five FQs (ofloxacin, enoxacin, ciprofloxacin, enrofloxacin, and sarafloxacin) and oxytetracycline were detected. Lower detection frequencies of antibiotics were observed in the marine fish. The concentrations of ΣFQs ranged from not detectable (nd) to 130 ng/g wet weight (ww) (median, 7.2 ng/g ww), and the concentration range of ΣTCs was nd to 200 ng/g ww (median, nd ng/g ww). The Chinese snakehead contained the highest concentrations of ΣFQs (130 ng/g ww) and the small yellow croaker accumulated the highest concentrations of ΣTCs (200 ng/g ww), respectively. Although the calculated estimated daily intakes (EDI) suggested that the consumption of these cultured fish from this region was not associated with significant human health risks, this study provides useful information that will be helpful in the appropriate antibiotic use in aquaculture. To our knowledge, this can be the first report on the occurrence and levels of antibiotics in cage-cultured marine fish from the Bohai Rim region, China.

Determination of 16 mycotoxins in vegetable oils using a QuEChERS method combined with high-performance liquid chromatography-tandem mass spectrometry.

A simple and efficient method for determining multiple mycotoxins was developed using a QuEChERS (quick, easy, cheap, effective, rugged and safe)-based extraction procedure in vegetable oils. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used for the quantification and confirmation of 16 chemically diversified mycotoxins. Different extraction procedures were studied and optimised by spiking 16 analytes into blank matrix, and the extraction with 85% MeCN solution and C18 as cleaning sorbent allowed an efficient recovery of 72.8-105.8% with RSDs less than 7%. The limit of detection (LOD) ranged from 0.04 to 2.9 ng g-1. The developed method was finally applied to screen mycotoxins in 62 vegetable oil samples. Zearalenone (ZEN), aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and α-zearalenol (α-ZOL) were detected, with maximum concentrations of 0.59 (AFG1)-42.5 (ZEN) ng g-1. The method developed has the advantages of high sensitivity, accuracy and selectivity, and it can be applied to the target screening of mycotoxins in real samples.