Correlation Between Exercise And Colonization Resistance Of Intestinal Flora To Pathogenic Bacteria And Antibiotic Effectiveness In Mice

Bacterial infectious diseases seems to be growing in frequency and become more difficult to treat due to the increasing antimicrobial resistance,not only in human society but also in animal farming.Therefore,it is imperative to develop new strategies to deal with infectious diseases,especially those caused by multidrug-resistant(MDR)pathogens.Meanwhile,living with the fast-paced life in modern society,the importance of sports has been paid more attention by the public for its benefits to our body,including enhancing immunity,improving cardiovascular function,accelerating metabolism,and improving cognitive ability,etc.,However,the potential correlation between exercise and the occurrence of bacterial infections and theeffectiveness of subsequent antimicrobial treatment,along with the role of the gut microbiota in these processes are still elusive.Based on this,this study constructed the model of exercise and excessive exercise in mice,and then evaluated the effect of exercise on the colonization of pathogens in vivo and the efficiency of the subsequent antibiotic treatment.Next,we analyzed the composition of mice intestinal microorganisms and the abundance and distribution of the altered metabolites among in mice with different motion state.Finally,we unraveled the mechanistic basis between the altered key metabolites and the antibiotic efficacy.To be first,in order to construct the mice model of exercise and excessive exercise,we chose C57BL/6 mice as the model animal and established the mice exercise intervention model with different exercise intensities through the mice wheel fatigue machine.By measuring the blood routine and biochemical indexes of the mice model,we found that the content of reticulocytes in the blood of exercise mice was increased significantly,while what increased in the excessive exercise mice was the percentage of monocytes.Meanwhile,alanine aminotransferase and aspartate aminotransferase were increased both in exercise and excessive exercise mice.These results also indirectly confirmed that our exercise model was constructed successfully.Based on this successful mouse model,we subsequently performed intragastric infection to explore the effect of exercise and excessive exercise on intestinal colonization resistance,along with antibiotic treatment.We found that exercise,especially moderate exercise,could significantly reduce the colonization of drug-resistant Gram-positive bacteria MRSA T144 in the intestinal tract of mice,but had no significant effect on the colonization of drug-resistant Gram-negative bacteria E.coli B2.Moreover,moderate exercise was found to enhance antibiotic efficacy of E.coli B2 in male mice,but this observation was not applied to females.Generally,these results indicate that moderate exercise enhances the intestinal colonization resistance and the therapeutic efficiency of antibiotics,but this effect is dependent on the intensity of exercise,the species of pathogens and the gender of animals.After depleting the gut microbes of mice by antibiotic mixtures administration in drink water,the effect of exercise on antibiotics efficacy was dismissed,suggesting that the modulation of intestinal microbes may play an important role in this process.Based on this,we performed the gut microbiota profiling and the untargeted metabolomics of its metabolites.The results showed that exercise reprogrammed the microbial composition,structure and species abundance of mice intestinal tract,as well as improved the ?-Diversity and ?-Diversity of intestinal tract.Moreover,the bacteria significantly increased in the moderate exercise mice were mainly centered on Eggerthellaceae and Marinfiliaceae,while the excessive exercise group was characterized as the over enrichment of Aerococcaceae.Therefore,there are significant differences in the remodeling of intestinal microbiota by different degrees of exercise.Next,we further conducted metabonomic analyses on the fecal samples of 102 mice from three groups of male and female.These results showed that exercise could change the metabolic pathways and the level of related metabolites in both male and female mice,and the key differential metabolites were mainly distributed in lipids and lipid molecules,organic acids and their derivatives and organic heterocyclic compounds.Among 251 metabolites with significant differences,we screened 16 metabolites related to amino acids,indoles and bile metabolism for further investigation.To explore the underlying mechanism of the altered gut microbiota and related metabolites on colonization resistance and the antibiotic efficacy,we further assessed the effects of these 16 metabolites on bacterial growth and antibiotic efficacy.We found that Lserine effectively potentiated antibiotic activity against Gram-negative bacteria.Mechanistic investigation showed that L-serine can significantly activate bacterial metabolism,which is manifested in the significant increase of bacterial respiration,ATP and ROS production,thus improving the efficiency of antibiotics.In conclusion,our study revealed that moderate exercise can regulate the host's colonization resistance to pathogens and the efficiency of antibiotics by modulating the relative abundance and diversity of intestinal microbiota of mice and the downstream metabolites.The representative metabolites L-serine can improve the bactericidal activity of antibiotics by stimulating the bacterial metabolism.