Effects Of Sulfonamides,sulfonamide Potentiators And Nano-silver On The Conjugation Transfer And Mutation Of E.coli And Preliminary Study Of Mechanism

Antibiotics are great discovery in the history of human medicine.In addition to clinical use,they also play an important role in the prevention and treatment of infectious diseases of animals and the promotion of animal growth.Besides,antibiotics are widely used in agriculture and aquaculture.They are charged to the environment through many kinds of ways,such as livestock and poultry and aquaculture wastewater waste,as well as industrial waste water discharge and manure farming of production enterprises.With the frequent use of antibiotics in various industries and even long-term abuse,more and more bacteria have showed their resistance to antibiotics.There are two ways to bacteria to obtain resistance,which are the acquisition of self-gene mutations and drug resistance genes.The main way to obtain resistance genes is the transfer of plasmids.In order to solve the problem of bacterial resistance,people have tried to reduce the use of traditional antibiotics and find better alternatives.For example,nano-silver（Ag NPs）is widely used in production and life because of its high antibacterial properties and no bacterial resistance.Studies have shown that the combination of Ag NPs and antibiotics can improve the efficacy of medicine,which is also a method to reduce the amount of traditional antibiotics.However,the combined effects of Ag NPs and antibiotics on the formation and spread of antibiotic resistance genes（ARGs）are not clear yet.Therefore,in this paper,Escherichia coli（E.coli）was used as a model organism to study the single and combined effect of Sulfonamides（SAs）,Sulfonamide potentiators（SAPs）and nano silver on RP4 plasmid conjugation transfer and on the mutations of E.coli,which is of great significance for understanding the environmental pollution and risk assessment of antibiotics and their resistance genes.The main research contents and results are as follows:（1）It was determined that the effects of single exposure of 12 sulfonamides（SAs,including SQ,SSZ,SMR,SPY,SMX,SCP,SD,SM,SMM,SDX,SMP,and SMZ）,three sulfonamide potentiators（SAPs,including DVD,OMP,and TMP）and nano silver（Ag NPs）on E.coli RP4 plasmid conjugation transfer,and the joint effects of Ag NPs combined to 12 SAs and 3 SAPs,respectively,on E.coli RP4 plasmid conjugation transfer.The results showed that 12 SAs,3 SAPs and nano-silver could significantly promote E.coli RP4 plasmid conjugation transfer,and the addition of nano-silver to a single SA or SAP could reduce the concentration of reaching the conjugation transfer P_max.Their joint exposure has a greater impact on the spread of antibiotic resistance genes in the environment.（2）The resistance mutations of 12 SAs,3 SAPs and Ag NPs on E.coli were studied.The mutation effect of sulfonamide on E.coli may be due to the effect of SAs,which in the folate synthesis pathway have a mutation-promoting effect on E.coli,thereby affecting the mutation rate of E.coli.In addition,all of the three SAPs（DVD,OMP,and TMP）could promote the mutation effect of E.coli.Moreover,the mutation frequency promotion rate MP_max of the three kinds of SAPs was DVD>TMP>OMP.The concentration of Ag NPs mutation frequency promotion rate is 2.22E-7 mol/L.（3）It has been determined that the correlation between SAs and Ag NPs on E.coli RP4 plasmid conjugation transfer joint effect,E.coli mutation joint effect and combined toxical effect.From the results,there was a good correlation between the three of them.Besides,when bacteria accelerate the transfer and mutation of plasmids under the action of SAs,the proliferation of bacteria will be delayed.In this paper,the research on the rule of the production and spread of antibiotic resistance genes by different concentrations of antibiotics and nano silver will help us to better understand the environmental effects and harms of antibiotics and their resistance genes,providing theoretical basis and technical support for the environmental risks and management of antibiotics.