Microalgae can promote antibiotic removal, which has attracted growing attention. However, its synergistic removal performance with bacteria in antibiotic pollutants is still poorly understood. In this study, firstly, we selected two green algae (Dictyosphaerium sp. and Chlorella sp.) and exposed them to Enrofloxacin (ENR) to observe their extracellular polysaccharides (EPS) concentration dynamic and the removal of antibiotics. Secondly, EPS was extracted and added to in situ lake water (no algae) to investigate its combined effect with bacteria. The results indicate that both Dictyosphaerium sp. and Chlorella sp. exhibited high tolerance to ENR stress. When the biomass of microalgae was low, ENR could significantly stimulate algae to produce EPS. The removal rates of Dictyosphaerium sp. and Chlorella sp. were 15.8% and 10.5%, respectively. The addition of EPS can both alter the microbial community structure in the lake water and promote the removal of ENR. The LEfSe analysis showed that there were significant differences in the microbial marker taxa, which promoted the increase of special functional bacteria for decomposing ENR, between the EPS-added group and the control group. The EPS of Dictyosphaerium sp. increased the abundance of Moraxellaceae and Spirosomaceae, while the EPS of Chlorella sp. increased the abundance of Sphingomonadaceae and Microbacteriaceae. Under the synergistic effect, Chlorella sp. achieved a maximum removal rate of 24.2%, while Dictyosphaerium sp. achieved a maximum removal rate of 28.9%. Our study provides new insights into the removal performance and mechanism of antibiotics by freshwater microalgae in water bodies and contribute to the development of more effective water treatment strategies.

Much attention has been given to the safety and quality of aquatic products, including consuming Chinese mitten crab (Eriocheir sinensis), which offers both nutritional benefits and toxicological risks. Eighteen sulfonamides, 9 quinolones and 37 fatty acids were analyzed in 92 crab samples from primary aquaculture provinces in China. Enrofloxacin and ciprofloxacin have been mentioned as typical antimicrobials occurring at the greatest concentrations (>100 μg/kg, wm). By use of an in vitro method, the proportions of enrofloxacin, ciprofloxacin and essential fatty acids (EFAs, DHA and EPA) in ingested nutrients were determined to be 12 %, none and 95 %, respectively. The risk-benefit quotient (HQ) between the adverse effects of antimicrobials and nutritional benefits of EFAs in crabs found that HQs based on data after digestion were significantly less (HQ = 0.0086) than that of the control group where no digestion occurred (HQ = 0.055). This result suggested that (1) there was less risk posed by antimicrobials due to the consumption of crab, and (2) ignoring the bioaccessible fraction of antimicrobials in crabs might overestimate risks to the health of humans due to dietary exposure. Meaning bioaccessibility can improve the accuracy of the risk assessment process. Realistic risk evaluation should be recommended to achieve a quantified assessment of the dietary risks and benefits of aquatic products.

Extensive and high residue variations in enrofloxacin (ENR) exist in different aquatic products. A novel quantitative method for measuring ENR using high-performance liquid chromatography-tandem mass spectrometry was developed employing enrofloxacin-d5 (ENR-d5) and enrofloxacin-d3 (ENR-d3) as isotope surrogates. This reduced the deviation of detected values, which results from the overpass of the linear range and/or the large difference in the residue between the isotope standard and ENR, from the actual content. Furthermore, high residue levels of ENR can be directly diluted and re-calibrated by the corresponding curve with the addition of high levels of another internal surrogate without repeated sample preparation, avoiding the overflow of the instrument response. The validation results demonstrated that the method can simultaneously determine ENR residues from MQL (2 µg/kg) to 5000 × MQL (method quantification limit) with recoveries between 97.1 and 106%, and intra-precision of no more than 2.14%. This method realized a wide linear calibration range with dual deuterated isomers, which has not been previously reported in the literature. The developed method was successfully applied to the analysis of ENR in different aquatic products, with ENR residue levels varying from 108 to 4340 μg/kg and an interval of precision in the range of 0.175~6.72%. These results demonstrate that batch samples with a high variation in ENR residues (over the linear range with a single isotope standard) can be detected by the dual isotope surrogates method in a single sample preparation process.

Avian pathogenic Escherichia coli (APEC) is the causal agent of colibacillosis, one of the most common bacterial infections in the poultry sector. Antimicrobial susceptibility testing (AST) is essential for rational and prudent antimicrobial therapy. Subsequently, uniformity in test results from the various testing methodologies used in diagnostic laboratories is pivotal. The aim of this study was therefore to evaluate the agreement between different AST methods in determining fluoroquinolone resistance in APEC. Twenty APEC isolates were selected and subjected to four different susceptibility tests: the quantitative microbroth dilution, agar dilution and gradient strip tests, and the qualitative disk diffusion method. The experiments were performed in triplicate. Categorical agreement, essential agreement and different errors were assessed. Moreover, agreement was also evaluated by calculating intraclass correlation coefficients (ICCs) for the quantitative tests and determining the Pearson correlation coefficients for the agreement between the disk diffusion method and the quantitative tests. Categorical agreement and essential agreement when compared with the microbroth technique ranged from 85-95% and 85-100%, respectively. No very major errors (false susceptible) and only one major error (false resistant) and minor errors (results involving an intermediary category) were detected. The calculated ICC values of the three quantitative tests fluctuated around 0.970 (range 0.940-0.988). There was a high negative correlation between the disk diffusion method and the other tests (correlation coefficients ranging from -0.979 to -0.940), indicating a clear inverse relationship between the minimum inhibitory concentration value and the zone diameter of growth inhibition. In conclusion, the overall agreement between the four different testing methodologies was very high. These results confirm the reliability of the disk diffusion and gradient strip test methods as substantiated alternatives, next to the gold standard agar and microbroth dilution, for fluoroquinolone susceptibility testing of APEC isolates.

暂无摘要。

暂无摘要。