Colonization Of Food-borne Antibiotic Resistant Bacteria In Human Gut And Its Effect On Intestinal Flora

Antibiotic resistance has been regarded as one of the major public health problems in the world due to the overuse of antibiotics in agricultural production,livestock and poultry breeding and clinical medicine.As the "repository" of antibiotic resistance genes,the composition of intestinal flora is closely related to human health such as nutrition metabolism,immunity and disease.Antibiotic resistant bacteria inevitably enter the human body through the food chain.At the same time,the residual antibiotics or other environmental pollutants in the human body can not only cause intestinal flora disorders,but also promote the transfer and spread of antibiotic resistant bacteria and antibiotic resistant genes,posing a potential threat to human health.However,the colonization,transmission mechanism and health risks of foodborne antibiotic resistant bacteria entering human intestines through the food chain are not clear.Therefore,by building human intestinal microbial ecosystem simulator(SHIME),fluorescence quantitative PCR technology and laser confocal microscope were used to dynamically track the colonization of exogenous resistant bacteria and under low concentration enrofloxacin stress.Based on metagenomic sequencing,the effects of exogenous bacteria on intestinal flora composition,bacterial resistance and pathogenicity were analyzed systematically.Study on the colonization of foodborne antibiotic resistant bacteria in human intestinal tract and the horizontal transfer of plasmid.The results showed that low concentration of enrofloxacin exposure promoted the colonization of antibiotic resistant bacteria in the intestine as well as the horizontal transfer of plasmid.The abundance of exogenous bacterial marker gene(mCherry)decreased by about 4.08-4.83 logarithmic units in the third segment of colon.Under the stress of low concentration of enrofloxacin,the gene abundance decreased by about 3.53-4.41 logarithmic units,indicating that exposure to enrofloxacin could promote the colonization of exogenous resistant bacteria in the intestinal tract.During the exposure period of enrofloxacin,the abundance of plasmid marker gene(gfp)decreased slowly,while the ratio of plasmid marker gene to exogenous bacterial marker gene(gfp/mCherry)increased,indicating that low concentration of enrofloxacin could promote the horizontal transfer of plasmid in the flora.At the same time,4 hours after the exogenous bacteria arrived in the ascending colon,green fluorescent bacteria were observed,indicating that the plasmid could be quickly transmitted to other intestinal bacteria through horizontal transfer.Study on the effect of foodborne antibiotic resistant bacteria on the structure and function of intestinal flora.The results showed that the entry of antibiotic resistant bacteria into human intestine through the food chain would destroy the balance of intestinal flora and increase the abundance of opportunistic pathogens.Antibiotic resistant bacteria and long-term exposure to enrofloxacin with low concentration of enrofloxacin could lead to changes in the community structure of intestinal flora,resulting in a significant increase in the value of F/B(Bacteroides/Bacteroides)and a significant decrease in Shannon index.The exposure of antibiotic resistant bacteria caused the abundance of Stenotrophomonas maltophilia to increase from 3.64% to 19.66%,becoming the dominant strain.After the treatment of fecal bacteria transplantation,the flora structure almost returned to the level of the initial environment.Under the stress of low concentration of enrofloxacin,the abundance of Megamonas funiformis increased from 7.03% to 26.40%,which became the dominant strain,but fecal bacteria transplantation could not restore the flora structure to the initial state.The main functional pathway of intestinal flora is Metabolism pathway,and the main carbohydrate enzyme is glycoside hydrolases.Study on the effect of foodborne antibiotic resistant bacteria on antibiotic resistance and pathogenicity of intestinal flora by macrogenomic sequencing.The results showed that antibiotic resistant bacteria could lead to the increase of antibiotic resistance genes in intestinal flora.After exposure to exogenous antibiotic resistant bacteria,the number of antibiotic resistant genes from 9294-9841 to 13649-14267,an increase of about 31.56%,which mainly promoted the increase in the abundance of msbA,PmrF,mdtC and mdtB.Low concentration of enrofloxacin as environmental selective stress mainly increased the abundance of kdpE and emrA.222 ARGs were annotated,which belonged to 22 types of antibiotics.Among them,there are at most 93 ARGs mechanisms of antibiotic efflux pumps,accounting for 41.9%.There are 19 antibiotic resistance gene hosts with horizontal transfer ability at species level,which are annotated as pathogenic bacteria,which pose a serious threat to human health and bring great challenges to clinical treatment.In this study,a SHIME system was built to clarify the effects and mechanisms of opportunistic pathogens on intestinal flora composition,antibiotic resistance genes and virulence factors based on fluorescence quantitative PCR and metagenomic sequencing.The results are helpful to reveal the colonization and transmission mechanism of foodborne antibiotic resistant bacteria after entering the human intestine,comprehensively evaluate the potential health risks of food contaminated by antibiotic resistant bacteria,and provide a theoretical basis for risk prevention and control of antibiotic resistant bacteria and antibiotic resistant genes in food environment.