| BackgroundPolyethylene glycol(PEG)is the most widely used intestinal cleanser in China.It is used for intestinal cleansing by forming an isotonic liquid via taking a large amount of liquid,What’s more,PEG has no effect on intestinal absorption and secretion during administration,and does not cause water-electrolyte disorders.Due to its outstanding safety and good tolerability,it is widely used for intestinal cleansing before colonoscopy or abdominal surgery.However,with the in-depth study of gut microbiota,it was found that the composition and abundance of gut microbiota were significantly altered in both mice taking small doses of PEG and volunteers taking large doses of PEG for intestinal cleansing.And it takes about 2 weeks for the gut microbiota restore to baseline levels after PEG was discontinued.It is well known that gut microbiota homeostasis plays an important role in preventing the colonization and growth of pathogenic microorganisms.Imbalance of intestinal commensal bacteria is an important cause of pathogenic bacteria colonization.However,there are still no literature on whether the changes in flora caused by PEG increase the risk of opportunistic infections.Enteropathogenic Escherichia coli(EPEC)and enterohemorrhagic Escherichia coli(EHEC)are important pathogenic factors causing infectious enteritis in humans,Citrobacter rodentium(C.R.)is an enteric pathogen unique to rodents and is often used to study EPECand EHEC-like pathology,because it can attach to the colonic mucosa and form attachment and effacing(A/E)lesions,colonic crypt hyperplasia,and diarrhea.Therefore,it is often used as a model to study the mechanism of intestinal infection in EPEC and EHEC.In wild-type mice,C.R.is a self-limiting infection that can be cleared approximately 21 days after infection.To investigate whether PEG increases the risk of intestinal infection,mice were gavaged with PEG for bowel cleansing,followed by infection with C.R.,then the degree of intestinal inflammation of mice were assessed.This study may provide more evidence for the safe application of PEG.Part Ⅰ.PEG increases the risk of C.R.infectionObjective:The purpose of this study was to explore the effect of PEG on the risk of intestinal infection during bowel preparation,as well as the duration of C.R.susceptibility after PEG.Methods1.Mice were were gavaged with PEG for bowel cleansing and infected with C.R.1 day later.Then C.R.load of feces,C.R.load of intestinal tissues,C.R.load of extra-intestinal tissues,virulence genes expression of C.R.and severity of colonic inflammation,the expression of inflammatory factors were assessed.2.Mice were gavaged with PEG for bowel cleansing and infected with C.R.on day 7 and 14 after PEG,respectively.Then C.R.load of feces,colonic histopathology score,and qPCR were performed to explore the duration of PEG-induced intestinal susceptibility window.ResultsThe C.R.load in feces of the PEG group was significantly increased compared to the control group,and the C.R.load of the small intestine and colon tissues was also significantly increased(p<0.001).there was also a significant increase in the load of extra-intestinal organs of C.R.,liver(p<0.01),mesenteric lymph nodes(p<0.01)and spleen(p<0.001).qPCR showed a significant increase in the expression of the virulence genes,Tir(p<0.001)and Ler(p<0.001)of C.R.in feces in the PEG group.In the experiment of C.R.infection 1 day post PEG,compared to the control group,the colon length of mice in the PEG group was significantly shorter(p<0.01),and the histopathological score of colon was severer(p<0.001),and the expression of the tight junction proteins(ZO-1 and Claudin)was reduced(p<0.001)on day 12 after infection of C.R..In the experiment of C.R.infected 7 days after PEG,the fecal load of mice in the PEG group was still significantly higher than that in the control group(p<0.001),the colon length was shortened(p<0.05),the histopathological score of the colon was severer(p<0.001),and the inflammatory factors TNFα(p<0.001)and IFNy(p<0.05)in the colon tissue were increased.However,in the experiment of C.R.infected 14 days post PEG,there were no significant differences in fecal load,colonic histopathological score,and expression of inflammatory factors(TNFα and IFNγ)compared to the control group.Conclusion1.PEG administration for bowel cleansing resulted in increased C.R.load and increased expression of C.R.virulence genes in mice.2.PEG administration for bowel cleansing aggravated intestinal inflammation induced by C.R..3.The time window of susceptibility to C.R.induced by PEG was 14 days.Part Ⅱ:PEG increases the susceptibility of C.R.by altering the structure of the gut microbiotaObjectiveThe purpose of this study is to explore whether altered gut microbiota is responsible for the increased risk of intestinal infections induced by PEGMethods1.Mice feces were collected and 16s rRNA sequencing was performed to analyze the changes in α-diversity and β-diversity of gut microbiota before and after PEG,and changes in specific bacteria at the genus level were analyzed.2.The feces of mice before PEG,1 day after PEG,3 days after PEG,7 days after PEG,and 14 days after PEG were collected and analyzed by 16s rRNA sequencing to explore the trend of gut microbiota after PEG.3.To investigate whether C.R.-induced infected enteritis could be alleviated by caging the mice of PEG group with untreated mice before infected with C.R.,fecal C.R.culture and colonic histopathological were assessed.Meanwhile,the feces of mice before PEG,7 days after PEG,and 7 days after PEG in co-housed cages were collected and subjected to 16s rRNA sequencing to further investigate the role of gut microbiota in PEG-induced intestinal susceptibility.ResultsIt was found that the a diversity and β diversity(p=0.004)of fecal flora in mice were reduced after apply of PEG for bowel preparation.Meanwhile,the abundance of Lactobacillus and Alistipes was significantly decreased and the abundance of Akkermansia and Escherichia Shigella was increased after PEG.The results of 16s rRNA sequencing analysis of mouse feces showed that the a diversity and β diversity of mouse gut microbiota gradually recovered to the pre-PEG level at 1,3,7 and 14 days after PEG at the OUT level,but still did not fully recover to the baseline level at 14 days after PEG.It was found that the fecal bacterial load and colonic histopathological score in the co-housing group have no significant difference from those of the control group after 7 days of combined cage feeding,thus confirming that combined cage feeding could reduce C.R.-induced infectious colitis after PEG.Meanwhile,the results of 16s rRNA sequencing analysis of feces showed that after 7 days of combined cages,the a diversity of mouse gut microbiota tended to the pre-PEG level at the OUT level,and the β diversity was not significantly different from the pre-PEG level,further confirming the important role of gut microbiota in post-PEG C.R.-induced infectious colitis.Conclusion1.PEG alter the gut microbiota in mice.2.After intestinal preparation with PEG,the gut microbiota structure of mice gradually recovered to pre-PEG level.3.Co-housing with PEG untreated mice improved the gut microbiota alteration caused by PEG and alleviated the infectious enteritis caused by C.R.Part Ⅲ Lactobacillus acidophilus reduces the risk of PEG induced infectious enteritis of C.R.ObjectiveThe purpose of this study was to explore whether supplementation with the probiotic Lactobacillus acidophilus(LAC)could reduce the risk of PEG-induced intestinal C.R.infections.MethodsMice were gavaged with PEG for bowel cleansing,followed by the administration of LAC gavage for 3 consecutive days,followed by C.R.infection.The fecal C.R.load and the colonic inflammation were assessed in both groups.The gut microbiota were assessed by 16s rRNA sequencing before PEG,3 days after PEG,and 3 days after application LAC.ResultsIt was found that the bacterial load of C.R.in the feces(p<0.001)and the colon pathology score(p<0.05)of mice were reduced after 3 days of LAC administration compared to the controls.The results of 16s rRNA showed an increase in fecal flora diversity in mice supplemented with LAC.Conclusion1.Supplementation with LAC can alleviate C.R.-induced infectious enteritis after PEG.2.Supplementation with LAC can accelerate the recovery of gut microbiota to baseline levels. |
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