| The occurrence of emerging environmental pollutants including antibiotics and antibiotics resistance gene has been identified as environmental challenges due to their potential ecotoxicological and public health effect.Over the last decade,there has been an increase in the consumption of antibiotics in low-and middle-income countries(LMIC).However,the occurrence of these contaminants is understudied in the environment of developing countries particularly in Sub-Saharan regions including Ethiopia,where many factors such as gross abuse and misuse of antibiotics,poor drug regulatory mechanisms,and inadequate and improper wastewater treatment facilities could likely contribute for the contamination of the environments by antibiotics residue which in turn may facilitate the possible pathways of propagation of antimicrobial resistance.Therefore,it is necessary to conduct more research on the region to help people fully understand the emergence and distribution of antibiotics and resistance genes.The study aimed to assess the contamination profile of commonly used antibiotics and the corresponding antibiotic resistance gene(ARGs)in sediment and agricultural soils from Awash river basin,Ethiopia.Sediment sampling was performed at 24 sites from the main course of the Awash River and its tributaries.For agricultural soils,samples were collected from 34 sites in the basin.Four tetracycline antibiotics(TC,OTC,DC,CTC),four sulfa antibiotics(SN,SME,SMX,SDZ)and four fluoroquinolones(OFL,CIP,ENR,NOR)were measured.The target antibiotics were extracted using solid phase extraction(SPE)method.The concentration of the antibiotics was determined by high performance liquid chromatography tandem mass spectrometry(LC-MS/MS).The relative abundance of the corresponding resistance gene and integron gene(intIl)was determined by Real time quantitative PCR(qPCR).Besides,the study aimed to assess the potential linkage between antibiotics,antibiotic resistance gene and environmental factors.The results of the study on the sediments indicated that,out of 12 studied compounds,sulfadiazine and enrofloxacin showed the highest and lowest detection frequency respectively.The total concentrations of the detected antibiotics ranged from 23.73-126.46 ug kg-1 dry weight(dw).High individual antibiotic concentrations of up to 62.39 ug kg-1 were measured for tetracyclines.Polymerase chain reaction(PCR)analysis revealed that tetA and tetB occurred in all the samples.The relative abundance of the resistant genes in sediment sample was in the following order:tetA>tetB>sul2>sull.Redundancy analysis result indicated that some sediment characteristics were correlated with sul1 resistance gene suggesting to have influence on its distribution.Use of manure in agricultural activity may have introduced antibiotics and thereby enhance ARGs in the soil environment.The results of the analysis in the agricultural soils samples revealed that,out of the 12 targeted antibiotics,eleven compounds were detected in the agricultural soil samples.TC and CTC were found to be the most predominant antibiotics.The total antibiotics concentration in the soil were found in the range from 1.52-22.72 ug kg-1 dw.The PCR analysis result showed that tetB and tetG were found to be detected in all samples.Positive correlation was also observed between total tetracycline concentration(TETs)and,the corresponding resistant gene(tetB and tetG).The potential ecological risk analysis in the soils highlighted that SDZ could pose high risk.In general,the study provided first-hand data on the prevalence and abundance of antibiotics and antibiotic resistance genes in the sediments and agricultural soils.Anthropogenic activities such as use of manure and wastewater and,industrial and hospital wastes might have contributed for the contamination of the soil by antibiotics.The study result can serve as an input to develop monitoring strategies to reduce further contamination and dissemination these emerging contaminants. |
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