The Protective Effects Of Probiotic Lactobacillus Casei Zhang On Antibiotic-induced Gut Dysbiosis In Rats And Its Mechanism

The long-term,excessive or frequent use of antibiotics can inevitably bring side effects,especially accelerating the emergence of drug-resistant strains;thus,it is meaningful to seek safe and effective dietary interventions to protect from such adverse effects.Lactobacillus(L.)casei Zhang is a well-studied koumiss-originated probiotic.Scientific evidence showed that this strain can colonize the human and animal guts and confer a wide variety of beneficial functions.Therefore,this study aimed to investigate the protective effects and mechanism of L.casei Zhang on the intestine after administrating antibiotics.Multiple parameters were monitored,including the levels of gut microbiota,serum and fecal metabolites,inflammatory factors,and short chain fatty acids.One week after acclimatization,SD rats were randomly divided into four groups(n=12 per group),and the experimental period was three weeks.The four groups were:AB-Prob,oral gavage with cefdinir(135 mg/kg)twice a day for 1 week and followed by oral gavage with L.casei Zhang(2.5×109 CFU/day)twice per day for 2 weeks;AB-Ctrl,negative control group receiving 0.85%saline solution after Lactobacillus treatment;AB+Prob,L.casei Zhang given three hours after cefdinir administration during antibiotic treatment;Ctrl,control group receiving oral administration of 0.85%saline solution twice per day during antibiotic and Lactobacillus treatment.Fecal and blood samples were collected on days 0,7,14,and 21,respectively.The main findings are as follows:(1)The probiotic intervention increased the ?-diversity of the gut microbiome post antibiotics administration.After taking antibiotics,the relative abundances of some antibiotic resistance-related bacteria,such as Enterococcus faecium,Vagococcus teuberi,Bacteroides thetaiotaomicron,Bacteroides ovatus,Clostridioides difficile,Burkholderiales,and the harmful bacteria Gordonibacter pamelaeae,increased significantly(p<0.05).The probiotic intervention reduced the abundances of these bacteria variably.During the recovery period,the proportion of some beneficial bacteria,such as Alistipes,Eubacterium,L.murinus,Parabacteroides goldsteinii,and L.casei,increased significantly(p<0.05)in the AB+Prob group.(2)The principal component analysis of the fecal metabolites of samples on day 7 also showed significantly different metabolome profiles from the other samples,indicating that antibiotics had a great impact on the profiles of intestinal metabolites.The degree of recovery of the AB-Prob and AB+Prob groups was better than that of the AB-Ctrl group,and the trend of recovery was from AB-Ctrl,AB-Prob,AB+Prob,followed by Ctrl.The administration of L.casei Zhang reversed the significant(p<0.05)alterations of fatty acid contents induced by antibiotics,prevented the increase in primary bile acids and the decreases in linoleic acid,secondary bile acids,succinic acid,and acetic acid caused by antibiotics,increased the substances that facilitate antibiotic excretion,increased the main amino acids that maintain normal intestinal function,and enhanced the metabolism of propionate to reduce the harmful effects of antibiotics.(3)For the AB+Prob group,the expression of serum CRP,IL-6,iNOS,TFN-?,IL-1?,and TNF-? decreased significantly(p<0.05),while the expression of DAO and IgG increased significantly(p<0.05).Although non-significant(p<0.05),the expression of the ileum butyrate receptor GRP109A increased in the AB-Prob group increased.The expression of the ileum tight junction proteins(Claudin-1,Occludin,and Zo-1)and the expression of the water and electrolyte exchange transporters(SLC26A3 and NHE3)increased in the AB+Prob group.In addition,for the AB+Prob group,the reduction in gut butyric acid caused by antibiotics was attenuated,and a higher magnitude of increase in the levels of SCFAs was observed during the recovery period.(4)The L.casei Zhang has undergone adaptive mutations and plasmid loss in the rat gut.At the same time,specific types of mutations related to the antibiotic intestinal environment occurred as well,and changes in the coding regions of these genes enhanced the survival of L.casei Zhang in the gut environment.Our results showed that L.casei Zhang could protect the gut environment from antibiotic pressure by regulating the intestinal microbiota and its key metabolites,reducing systemic inflammation,enhancing intestinal barrier integrity,enhancing intestinal water and electrolyte exchange,and maintaining the intestinal SCFAs levels.The current results have demonstrated the protective effects of probiotic intake from antibiotic-induced side effects from a novel perspective.This work also serves as evidence for the safe use of probiotics in an antibiotic-containing environment.