Study On Antibiotic Pollution,microbial Resistance And Biological Toxicity In Yitong River

At present,antibiotics are widely used in the field of prevention and treatment of human and animal infectious diseases.Antibiotics can enter various environmental media through a variety of ways,at the same time,bacterial resistance and antibiotics resistant gene pollution will be generated,which will cause adverse effects on the ecosystem and even human health.In this study,eight sampling sections were set up in the Yitong River,which is a secondary tributary of the Songhua River.The concentrations of nine antibiotics including Sulfadiazine(SD),Sulfamerazine(SMD),Sulfadimidine(SM2),Sulfamethoxazole(SMZ)and Ciprofloxacin(CIP),Ofloxacin(OFX),Tetracycline hydrochloride(TCH),Oxytetracycline(OTC)and Trimethoprim(TMP)in different hydrological periods(August,November 2016,and May 2017)was tested,the concentrations of antibiotics in three sewage treatment plants in Changchun of different month(May,August and October)were studied;the space-time distribution features and pollution characteristics of antibiotics were analyzed,and the ecological risks were evaluated.The resistance of microorganisms to typical antibiotics,the distribution of antibiotics resistance genes,and the toxic effects of antibiotics on organisms(photoluminescent bacteria)were studied,which provided a scientific basis for the comprehensive evaluation and treatment of antibiotics pollution in Yitong River.The main results are as follows:(1)In order to study the possible impact of sewage treatment plant drainage on the receiving river,the residues of nine antibiotics in the inlet and outlet of three sewage treatment plants in Changchun city were determined.The results showed that seven kinds of antibiotics were detected in the inlet of the three sewage plants,with an overall detection rate of 23.46%.The sequence of detection rate from high to low was: TMP(55.56%)?OFX(44.44%)?CIP = SD(33.33%)?SMZ(22.22%)?OTC = TCH(11.11%),of which the concentration of TMP was the highest(1.269 ?g/L).Eight antibiotics were detected at the outlet,with a total detection rate of 16.05%.The sequence with the highest detection rate from high to low was: TMP(33.33%)= CIP?SMD(22.22%)?OFX = SD(11.11%)= SMZ = OTC = TCH,and the concentration of SD was the highest(1.612 g/L).The order of the total detection rate of antibiotics in three sewage plants in three months was: August(25.92%)?May(18.52%)?October(3.70%).The evaluation results of RQs showed that antibiotics with high risk and potential harm to water ecology from sewage treatment plants were CIP,OFX and SMZ,while those with medium risk were OTC,TCH and SD.(2)The detection results of antibiotic residues in 8 sections of Yitong River for three hydrographic periods showed that the concentration ranges of nine antibiotics in Yitong River were nd-1.361 ?g/L.The detection rate and concentration of fluoroquinolones were 54.16% and 0.221 g/L,respectively.The detection rate(62.50%)and concentration(1.361 g/L)of OFX was the highest.The detection rate and concentration of sulfonamides were 22.92% and 0.054 g/L,respectively.The concentration of SMD was the highest(1.083 ?g/L),and the detection rate of SD was the highest(37.5%).The detection rate of trimethoprim was 33.33% with the highest concentration of 0.393 ?g/L.OTC of tetracyclines had a detection rate of 4.16% at a concentration of 0.024 ?g/L.The detection rate and concentrations of antibiotics in the flood period and the drought period were higher than those in the normal river period.The total detection rate of antibiotics in the three hydrographic periods from high to low was drought period(12.04%)?flood period(8.79%)?normal river period(4.17%).The total detection rate of OFX in the drought period was 100%.From the perspective of space,among the eight sample sections,the concentrations of antibiotics in the water close to the urban area were relatively high.The risk assessment of antibiotic showed that CIP,OFX and SMZ were antibiotics with high risk and SD had the medium risk.(3)The antibiotic resistance of total coliforms and Escherichia coli in Yitong River water was studied by using the improved Colilert method and Kieby-Bauer method.The results showed that the total coliforms in the flood period and the drought period in Yitong River were significantly higher than those in the normal river period.The inhibition rates of SOX,TCH and TMP on total coliforms in Yitong River did not change significantly with the hydrological periods,while CIP,OFX and ENR showed obvious seasonal change on total coliforms in most sections of water.The inhibition rate was 18.654.7% in the flood period and drought period.The highest inhibition rate(89.5%)was obtained in the normal period.The total coliforms of Fluoroquinolone contaminated sections in the flood period and drought period still showed high resistance in the normal river period.There were seasonal differences in the resistance rates of E.coli to most antibiotics,and its resistance rate to Fluoroquinolones was lower.The high resistance rate of E.coli to Tetracycline in the flood period water was 68.8%.Multi-antibiotics resistant E.coli were detected in all of 8 sections in three hydrological periods.(4)Quantitative Real-time polymerase chain reaction was used to study the distribution of antibiotics resistance genes in eight sections of Yitong River.Correlation analysis was conducted with the total coliform antibiotics resistance measured by the improved Colilert method.The results showed that sul1,sul2 of Sulfanilamide,dfra1 of TMP and tet Q of Tetracycline were the main antibiotics resistant genes in Yitong River.The relative abundance of tet M,tet O and tet Q and qnr A in Yitong River were significantly negatively correlated with the highest inhibitory rates of total coliform group with antibiotics,indicating that these antibiotics resistant genes may be originated from total coliform group.(5)The acute toxicity of Fluoroquinolones,TMP,Sulfonamides and Tetracyclines to Vibrio qinghaiensis sp.-Q67 was determined.The dose-time-response relationships of antibiotics to Vibrio qinghaiensis sp.-Q67 were investigated.The time-dependent joint toxicity of Fluoroquinolones,Tetracyclines and TMP to Vibrio qinghaiensis sp.-Q67 were studied.The results showed that the acute toxicity of single antibiotic to Vibrio qinghaiensis sp.-Q67 was Tetracyclines? Fluoroquinolones ? TMP = Sulfonamides.The toxicity of various antibiotics to Vibrio qinghaiensis sp.-Q67 showed a time-effect relationship within the experimental concentration range.SOX and SDM showed obvious Hormesis effect within 8 h in the concentrations range of 0-0.002 mol/L.The joint toxicity of antibiotics binary mixture to Vibrio qinghaiensis sp.-Q67 varied with the mixing proportion and time.At 4 h,8 h and 12 h,the joint toxicity of most binary mixtures to Vibrio qinghaiensis sp.-Q67 mainly showed an additive effect at low concentrations.The joint toxicity of TCH and OTC showed a synergistic effect at low concentrations,and an additive effect at high concentrations.The joint toxicity of Tetracyclines and TMP to Vibrio qinghaiensis sp.-Q67 was additive at low concentrations and antagonistic at high concentrations.