Bioconcentration,Biotransformation And Multicompartmental Toxicokinetic Model Of Antibiotics In Sea Cucumber

Mariculture,riverine transport and discharge from land-based sources have led to ubiquitous occurrence of antibiotics in coastal seawaters.Antibiotics can lead to bacterial resistance.Therefore,it is necessary to investigate bioconcentration and biotransformation of antibiotics in mariculture organisms,which is of importance to guide healthy mariculture and assess risks of antibiotics.Sea cucumber(Echinodermata,Holothuroidea)is one of main mariculture species of economic significance in Asian countries,especially in China.However,it remains largely unknown whether antibiotics can be bioaccumulated and biotransformed in sea cucumbers,and toxicokinetic models for Echinodermata are also lacking.In this study,antibiotics that are frequently detected in coastal seawaters were selected as target compounds,and their analytical methods and occurrence were investigated.Bioconcentration and biotransformation of antibiotics in sea cucumbers were explored.Finally,a multicompartmental toxicokinetic model of antibiotics on sea cucumber was developed.The main research contents and results are as follows:(1)The analytical method for determination of antibiotics in sea cucumbers was developed.An accelerated solvent extraction(ASE)with in-cell clean-up method coupled to ultraperformance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)was developed to determine 21 antibiotics from six classes in sea cucumbers.The analytes include ten sulfonamides,four fluoroquinolones,three amphenicols,two beta-lactams,lincomycin and trimethoprim.Optimal parameters of the ASE in-cell clean-up method were at 80?,1500 psi,one static cycle of five min with methanol/acetonitrile(1/1,v/v)using 2 g of C18 as adsorbent.Recoveries at 50.1?129.2%were achieved with relative standard deviation under 22.3%.The method detection limits were in the range of 0.03?2.9?g·kg-1.(2)The occurrence and residual levels as well as health risk assessment of antibiotics in sea cucumbers products were explored.Occurrence of the target antibiotics were screened in 33 dry and 16 instant sea cucumber samples collected from four sites in China.The samples were simultaneously extracted and purified using ASE in-cell clean-up and analyzed by UPLCMS/MS.Ten antibiotics were detected in the sea cucumber samples with the maximum concentration of 32.8 ?g·kg-1 dry weight for sulfamethoxazole.Sulfonamides are predominant antibiotics,followed by macrolides and fluoroquinolones.Geographical region-dependent antibiotics pollution was observed in sea cucumbers collected from different seawaters based on principal component analysis.It was also found that the antibiotic levels are slightly higher in instant sea cucumbers than the dried ones.Hazard quotient calculation suggested health risks associated with antibiotics exposure due to consumption of the sea cucumbers are acceptable.(3)The bioconcentration and biotransformation of seven antibiotics(sulfadiazine,sulfamethoxazole,enrofloxacin,ofloxacin,trimethoprim,clarithromycin and azithromycin)in sea cucumbers were investigated.Laboratorial antibiotic exposure experiments on juvenile sea cucumbers(Apostichopus japonicus)were performed under semi-static conditions,and the bioconcentration factors(BCFs)were calculated.Field sea cucumber and surrounding seawater samples were also analyzed,and the bioaccumulation factors(BAFs)were estimated.Results show that the sea cucumbers tend to accumulate high concentrations of the antibiotics with the maximum BCF value up to 1719.7 L·kg-1 for ofloxacin.The BCF values determined in the laboratory deviate less than 10-fold from the BAFs obtained in the field.Seven biotransformation products of the antibiotics were identified.The biotransformation products were mainly found in the digestive tract,indicating its high capacity in biotransformation.(4)The multicompartmental toxicokinetic model of antibiotics on sea cucumbers was developed.The multicompartmental toxicokinetic model was developed based on principles of passive diffusion and mass balance considering five compartments,body wall,mouth,digestive tract,respiratory trees,and coelomic fluid.88%of the model predictions deviate less than 5fold from the measured concentrations,and 99%of the predicted concentrations deviate less than 10-fold,indicating that the prediction accuracy of the multicompartmental toxicokinetic model is pretty good.The results indicated that principle of passive diffusion is suitable to construct multicompartmental toxicokinetic models on sea cucumber,and the developed model can successfully predict time-course concentrations of the antibiotics in different tissues of sea cucumbers.This study aims to establish analytical methods for antibiotics in sea cucumbers and to report bioconcentration and biotransformation of antibiotics,and to develop multicompartmental toxicokinetic model on sea cucumbers.The findings may offer a scientific basis for guiding healthy mariculture of sea cucumbers and assessing risks of antibiotics.