The antibiotics sulfamethoxazole (SMZ) and enrofloxacin (ENF) are commonly used in aquaculture in China, but their effects on the primary productivity of phytoplankton are unclear. On the basis of the fishery drug use standards (SMZ, 100 mg kg−1 d−1; ENF, 15 mg kg−1 d−1), these antibiotics were put into culture ponds to observe their effects on the phytoplankton community and primary productivity. The results showed that the changes in phytoplankton species at SMZ and ENF sites were different. At the ENF sites, Bacillariophyta species increased from 7 to 9, euglenophyta from 8 to 12 and cyanophyta from 11 to 9. Chlorophyta species at the SMZ sites increased from 10 to 15 and euglenophyta from 7 to 4. SMZ and ENF significantly promoted the number of cyanophyta (p < 0.05). The promoting effect of SMZ was more obvious than that of ENF. SMZ was more effective than ENF in promoting cyanophyta. The maximum number of cyanophyta at SMZ sites was 52.39 million L−1, and the concentration of SMZ was positively correlated with the number of cyanophyta. The maximum number of cyanophyta at ENF sites was 33.13 million L−1, and the promoting effect of low concentrations was more significant than that of high concentrations. Both SMZ and ENF promoted increased phytoplankton biomass, consistent with the residual time of the antibiotics in the aquaculture environment. The greatest biomass at the SMZ sites was 129.31 g m−³, and that at the ENF sites was 117.85 g m−³. The changes in the α diversity index showed that both SMZ and ENF led to a decrease in phytoplankton biodiversity, and that SMZ was more harmful to it. There were significant differences in the Shannon–Wiener, Pielou and Simpson indexes of the SMZ sites within groups (p < 0.05). The β diversity index showed that both antibiotics could change the phytoplankton habitat, but the effect of ENF on the habitat was recoverable, while that of SMZ prevented its restoration. These data will be valuable in protecting the ecological environment of fisheries and ensuring the safety and stability of fishery aquatic ecosystems.
Antibiotics have been commonly used as antimicrobial agents in the process of aquaculture worldwide. However, very few studies are available on the endocrine disruption-related health risks brought about by antibiotic residues from human consumption of aquatic products. Nuclear hormone receptors (NHRs) could mediate many endocrine-disrupting activities. Therefore, in the present study, a reverse docking method was used to predict the direct binding interactions between 16 NHR conformations and 15 common antibiotics in aquaculture, thereby determining their potential endocrine-disrupting risks. To reach a compromise between the extremely scarce experimental data and an urgent need for distinguishing antibiotics of high concern with potential food-borne endocrine-disrupting risks in aquaculture, a risk-ranking system was then developed based on a comprehensive risk score for each category of antibiotics, which was the sum of the products of endocrine-disrupting potential coefficients and annual usages of antibiotics in aquaculture. The results indicated that 15% of 224 docking simulations showed a relatively high probability of binding. Sulfonamides seemed to possess the greatest endocrine-disrupting potential. The antagonistic conformation of the androgen receptor was the most susceptible NHR conformation. The rank orders of the endocrine-disrupting risk of different categories of antibiotics varied greatly from country to country, which were significantly affected by the annual usage. These findings pose questions regarding public health and safety associated with human consumption of antibiotic-containing aquatic products. In addition, we provide an approach to rank antibiotics for a specific country or region, with respect to their potential endocrine-disrupting activity, that can be used to inform regulation and prioritize experimental verification.
Background Sulfamethoxazole (SMZ) is an antibiotic used globally to treat fish disease in aquaculture, but the effects of exposure to legal aquaculture doses of SMZ in fish are still unclear. To comprehensively investigate the effects of exposure to legal doses of sulfamethoxazole (SMZ) in Nile tilapia (Oreochromis niloticus), fish were exposed to diets supplemented with different doses of SMZ (blank group, normal feed; LS, 0.67 g/kg; MS, 6.67 g/kg and HS, 33.33 g/kg) for 4 weeks. General SMZ accumulation, growth performance, physiologic status, intestinal and hepatic health were systemically evaluated. Results The exposure experiment indicated that the SMZ accumulation in O. niloticus muscles, intestinal and aquaculture environment were positively related to the exposure dose. And withdrawal of antibiotics feed after 4th week, the SMZ residual in fish muscles, aquaculture water and sediment gradually decreased to safe level. LS and MS amount of antibiotics promoted the growth of fish accompanied by reduced feed coefficient in treated groups, while the fish growth in HS group was retarded. Exposure of O. niloticus to SMZ also increased the content of TG, promoted liver hypertrophy, and increased number of fat particles in liver. Antibiotics changed the content of intestinal short-chain fatty acids (SCFAs), and the changes in acetic acid were the most obvious. SMZ exposure reduced the biological diversity of the intestinal flora subsequently induced microbiota dysbiosis, and the degree was positively related to the exposure doses, and the experimental mainly inhibiting the growth of Fusobacteria. Conclusions Overall, exposure to of fish to legal doses of SMZ impair general physiological functions, intestinal flora and provokes health risk in fish. This study highlights the importance of rational and regulated use of SMZ in aquaculture.
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