Study On The Combined Toxicity And Physiological And Biochemistry Effects Of Disinfectants And Antibiotics On Escherichia Coli

In recent years,disinfectants have been overused,which has caused an increase in their residue in the environment.This could potentially harm the ecological environment and human health.Additionally,antibiotics,a new type of pollutant,have exceeded safe levels in some lakes and groundwater.When disinfectants and antibiotics mix,they form a complex mixture that can cause even greater pollution and risks to the environment.This could have serious effects on the ecological chain and human health.Therefore,three guanidine disinfectants（chlorhexidine（CHL）,metformin（MET）,and chlorhexidine（CDE））and six antibiotics（three aminoglycoside antibiotics:abramycin sulfate（APR）,dihydrostreptomycin（DIH）,neomycin sulfate（NEO）,and threeβ-lactam antibiotic:amoxicillin（AMO）,meropenem（MER）,and cefoperazone（CEF））were selceted as the research objects,and Escherichia coli（E.coli）was as the test organisms.The binary and multicomponent mixture systems were designed by using the direct equipartition ray design（Equ Ray）and uniform design ray（UD-Ray）methods,respectively.The concentration-toxicity data of six antibiotics and three guanidine disinfectants and their mixture systems at five different exposure times（0.25,2,4,8 and 12 h）were determined by the time-dependent microplate toxicity analysis method（t-MTA）.Concentration addition（CA）model was used to analyze the toxicity interaction,and a return-to-zero fitting method was used to quantitatively characterize the intensity of toxic interaction.The response of physiological and biochemical indicators such as soluble protein dissolution,electrical conductivity parameters,size of bacteriostatic zone,as well as cells morphology changes in E.coli cells were also investigated to reveal the possible toxicity mechanism of pollutants and their mixture systems.The main conclusions of this paper are as follows:（1）Three guanidine disinfectants（CHL,MET,CDE）and six antibiotics（APR,DIH,NEO,AMO,MER,CEF）showed good concentration-effect relationship to E.coli,and t-CRCs showed"S"type with significant time and concentration dependence.Specifically,the toxicity augmented with the prolongation of time,and the toxicity increased with the concentration when at the same exposure time.（2）The toxicity of binary and ternary mixtures of the three guanidine-based disinfectants（CHL,MET,CDE）against E.coli varies significantly,with the p EC₅₀value ranging from 1.61～5.63.The maximum antagonistic intensity of MET-CDE and CHL-CDE appeared in the shorter exposure time（2～4 h）,and the maximum antagonistic intensity of CHL-MET and CHL-MET-CDE appeared in the longer exposure time（8～12h）,and the maximum intensity was 40.49%.（3）The binary and ternary mixtures of three aminoglycoside antibiotics（APR,DIH,NEO）were effective against E.coli showed significant inhibitory effect,p EC₅₀=4.24～6.09.The binary and ternary mixture systems showed synergistic or antagonistic effects,and all showed similar rules of toxic interaction:at the same concentration,with the extension of time,the interaction intensity first increased and then decreased.The maximum intensity of antagonism was 15.70%,while the maximum intensity of synergy was 35.34%.（4）Three kinds ofβ-lactam antibiotic and their ternary mixtures（AMO-MER-CEF）were effective against E.coli and had obvious toxicity effect,p EC₅₀=3.57～6.40.Only AMO-MER showed antagonistic effect in binary and ternary mixture systems,while AMO-CEF,MER-CEF and AMO-MER-CEF showed significant synergistic effect.The intensity of toxic interaction showed the same change rule.At the same concentration,the intensity of antagonistic or synergistic effects increased at first and then decreased with time.The maximum intensity of antagonism was 18.06%,and the maximum intensity of synergy was 37.13%.（5）The complex mixtures of six and nine components composed of three guanidine disinfectants,three guanidine disinfectants and threeβ-lactam antibiotics had certain toxic effects on E.coli with p EC₅₀values ranging within 1.25～5.65,and the time dependence and concentration-ratio dependence of some system mixtures on E.coli are different.The interaction types of six-component and nine-component complex mixtures mainly showed antagonistic or synergistic effects.Some rays in guanidine disinfectant and aminoglycoside antibiotic（CHL-MET-CDE-APR-DIH-NEO）system showed antagonistic transition to synergistic effect,while some rays in aminoglycoside antibiotic andβ-lactam antibiotic（APR-DIH-NEO-AMO-MER-CEF）system showed antagonistic transition to additive effect.The others showed antagonistic effect in guanidine disinfectant andβ-lactam antibiotic（CHL-MET-CDE-AMO-MER-CEF）and nine-component mixture（CHL-MET-CDE-APR-DIH-NEO-AMO-MER-CEF）system,and the antagonistic effect intensified with time.The antagonistic intensity CHL-MET-CDE-AMO-MER-CEF-APR-DIH-NEO and APR-DIH-NEO-AMO-MER-CEF was 56.77%and 34.66%respectively.（6）After the nine pollutants and their reprehensive mixture rays treated,the soluble proteins of E.coli cells showed efflux,the conductivity and TDS increased with time,and the resistivity was inversely proportional to time.After exposed to the same EC_xof pollutants,E.coli had different sensitivity to different pollutants.The cells of E.coli appeared ellipsoidal,convex fold,broken adhesion and incomplete outer wall.Figure[86]table[35]references[105]...