| Discovery and development of antibiotics bring large benefits to human beings,such as preventing and treating of infections and avoiding widely spreading of epidemics,thus increasing the human’s health and life expectancy.Antibiotics are also widely used in agriculture and animal husbandry to reduce infection and promote the growth of animals,thus bring economic benefits to humans.Overuse of antibiotics causes for the widely spreading of antibiotic resistance,which affects people’s life and health.Drug resistance has gradually attracted worldwide attention,because antibiotics and resistance gene can be detected in lots of environments,such as soil,water and air.Water environment is closely related to human beings.People have detected a variety of antibiotics likes sulfonamides and drug resistance genes in in various water environments,even in drinking water.There is no effective way to remove drug-resistant genes,let them enter into the body with the water ingestion.Many mobile genetic elements contain resistance genes,including integrons,transposons,and plasmids.Plasmids are self-replicating and have a flexible form.Particularly,Conjugate-transfer plasmids usually carry a variety of drug-resistant genes for horizontal transfer.Horizontal transfer of drug resistance genes is one of the main mechanisms to promote the spreading of drug resistance,and plasmid-mediated horizontal transfer of drug resistance genes is the most important part of this mechanism.Intestinal microbiota is the most important part of human microorganisms and is closely related to human diseases,including depression,diabetes,and tumors.It has received widespread attention in recent years.As the body’s largest microbial library,gut microbiota is closely associated with drug resistance.Intake of antibiotics or resistant genes from outside environments may affect the composition,abundance,variety and drug-resistance of intestinal microbiota..There are many studies about the effects of antibiotics on the resistance of intestinal microorganisms.Many investigations have found that vectors carrying drug-resistant genes can enter the gastrointestinal tract through the resistance mechanism of the gastrointestinal tract and have biological activity.Gastrointestinal tract not only provides nutrients for microorganisms,but also serves as a matrix for horizontal transfer of drug-resistant genes.When drug-resistant genes transfer to intestinal pathogenic microorganisms,it will cause serious consequences.In this background,the affection of resistant genes in the water environment to the resistant of intestinal microbiota ought to be investigated.This article mainly investigate the effect of plasmid R55 with environmental concentration on gastrointestinal drug resistance in mice,and the response of intestinal microbiomes to antibiotics.This study primarily detected the conjugational transfer of R55 and then verified it’s transfer capacity between different species of bacteria.What’s more,drug-resistant genes sul1,sul2,and floR can be used as detection markers for in vivo experiments.Subsequent research used C57BL6 mouse as an in vivo model,unmodified R55 plasmids and sulfadiazine were injected into the mice by intragastric administration for 20 days and then stop for 15 days as recovery period.During the experiment,the contents of each part of the gastrointestinal tract of the experimental mice were obtained regularly and continuously.The changes of the drug resistance genes sull,sul2 and floR were detected by total DNA extraction and real-time fluorescence quantitative(RT-qPCR).Meanwhile,drug-resistant bacteria in the intestinal flora were screened and the transfer of R55 in the intestinal microbiota was detected with phenotypic direction.Results showed that the R55 plasmid with environmental concentration did not cause changes in the level of resistant genes in the intestinal flora in the short term,as well as genotype and phenotypic results.Interestingly,this research found that the levels of drug resistance genes of sulfadiazine increased in 8 to 12d during intragastric administration,and then declined.Moreover,the changes of drug resistance gene levels did not occur in the entire gastrointestinal tract,but in the stomach and large intestine.indicating that each part of the intestine has different responses to antibiotics.This "spatial-and temporal-confined "phenomenon indicates that the gastrointestinal tract has a complex dynamic mechanism,and it should be investigated respectively.Based on the effects of R55 plasmid with environmental concentrations and sulfadiazine to the resistance of mice intestinal microbiota,the responses of various parts of the intestinal microbiota to R55 plasmid and sulfadiazine were investigated.This research preliminary explores the influence of resistant genes with environment concentrations on intestinal resistance then studied the effect of antibiotics on the intestinal,in order to make people attach great importance of antibiotics and drug resistance gene pollution in the environment. |
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