Effect And Mechanisms Of Lactobacillus Rhamnosus In The Treatment Of Drug Resistant Escherichia Coli Infection

The emergence of multiple drug resistance(MDR)has brought great challenges to the development of new drug that can be efficient to inhibit resistant pathogens.Probiotics have advantages in wide antibacterial spectrum,diverse antibacterial mechanisms,and natural coexistence with human body.They have become a potential resource to explore drugs to treat drug-resistant bacterial infections.In this paper,Lactobacillus rhamnosus SHA113,a strain with great potential from healthy breast milk,was investigated in aspects of its efficacy and the mechanisms to treat intestinal infection caused by multi-drug resistant Escherichia coli QBQ009.According to the results,the following conclusions were obtained:(1)In vitro experiments showed that the growth and activity of drug-resistant E.coli could be effectively inhibited by the cells and cell-free supernatant of L.rhamnosus culture.The mechanisms for this were identified as two ways: one is L.rhamnosus coagulates with E.coli and reduces the cellular activity of E.coli;another one is L.rhamnosus produces proteins and bacterin metabolites to effectively kill E.coli.(2)The results of animal experiments showed E.coli infection caused inflammatory response and intestinal flora disorder,and the reactions caused by drug-resistant E.coli were more serious than non-drug resistant E.coli strain.L.rhamnosus treatment also rapidly reduced the number of infections of drug-resistant E.coli in vivo,eliminated inflammation,increased the total amount of lactic acid bacteria in feces,and reduced the abundance of proteobacteria in intestinal flora.However,treatment with antibiotic ampicillin could not effectively reduce the total amount of coliform in feces,but significantly reduced the total amount of lactic acid bacteria in feces and destroyed the intestinal microflora.These results indicate that L.rhamnosus has great potential to inhibit drug-resistant E.coli infection and restrore the balance of intestinal flora.(3)The results of H.E staining and immunofluorescence staining showed that L.rhamnosus could protect the intestinal tract and reduce the damage caused by drug-resistant pathogens.Observation of caco-2 ghostlike cyclic peptide staining,Western-blot detection and permeability detection showed that both of L.rhamnosus and E.coli caused changes of epithelial cytoskeleton,but E.coli could lead to decreased epithelial cell activity,while L.rhamnosus could promote epithelial growth and expression of tight junction proteins.The adhesion rate of L.rhamnosus to intestinal and Caco-2 cells was significantly higher than that of E.coli,but the presence of E.coli could significantly reduce the adhesion rate of L.rhamnosus.The self-aggregation ability of L.rhamnosus was significantly higher than that of E.coli,and it could co-aggregate with E.coli efficiently.More important,the activity of E.coli decreased significantly after the coaggregation,while the activity of L.rhamnosus was not affected after the coaggregation.Exopolysaccharides produced by L.rhamnosus could significantly reduce the permeability of intestinal tissues and Caco-2 cells,and increase the adhesion rate of E.coli to epithelial cells,but the effect was not significant in statistic.Meanwhile,it could promote the expression of tight junction protein ZO-1 in epithelial cells,but inhibit the expression of occludin protein.Taking all the results together,it was speculated that the fast reduction of living drug-resistant E.coli caused by L.rhamnosus via multiple ways might be the decisive factor for its effecient treatment of drug-resistant E.coli infection.The restoration of intestinal barrier and elimination of inflammation might be the result of the decrease of the number of pathogenic bacteria.