Screening Of Selenium-enriched Probiotics And The Therapeutic Effect On Endometritis

Endometritis is one of the common postpartum diseases in dairy cows,which can lead to decreased milk production and lower fecundity,severely limiting the development of cattle breeding.Clinically,the main treatment for endometritis in cows is the use of antibiotics,and long-term use of antibiotics can produce bacterial resistance,which can seriously affect the efficiency of endometritis treatment.With the advent of the "antibiotic-free" era,probiotics have the advantages of no contamination,no residue and no drug resistance.Therefore,they have emerged in people’s vision.Researchers also combine probiotics with trace elements or natural extracts to enhance their efficacy in new forms.The purpose of this paper is to investigate the combination of probiotics and selenium into selenium-enriched probiotics and to investigate the therapeutic effect of selenium-enriched probiotics on endometritis.First,55 strains isolated in the reproductive tract of healthy dairy cows in our laboratory were selected,which were initially screened and re-screened by using selenium containing solid medium and selenium containing liquid medium.Subsequently,the best strains were selected by testing their density,selenium content,and bacteriostatic effects on Escherichia coli(E.coli)and Staphylococcus aureus.After that,the strain sequences were detected by 16 S r DNA to confirm the genus of probiotic bacteria,and the screened strains were optimized for selenium enrichment conditions.Finally,a mouse endometritis model was established by using E.coli,which was treated with selenium,probiotics,selenium-enriched probiotics,selenium+probiotics,and antibiotics.To observe morphological changes of the uterus and histopathological changes of the uterus,the m RNA and protein expression of mouse interleukin 1β(IL-1β),mouse interleukin 6(IL-6),mouse tumor necrosis factor α(TNF-α),mouse interleukin 10(IL-10)and tight junction-related proteins(ZO-1,occludin)were detected by q RT-PCR,ELISA,western blot,and to clarify the therapeutic effect of selenium-rich probiotics on E.coli-induced endometritis in mice.The results of the study are as follows:1.Twenty selenium-resistant strains were obtained by primary screening of 55 strains,and re-screened by sodium selenite concentration,initial p H of the medium,incubation temperature,time,and selenium conversion rate,five strains of selenium-enriched probiotics were obtained,including one strain of Pediococcus acidilacti,two strains of Lacticaseibacillus paracasei,one strain of Pediococcus pentosaceus and one strain of Lactobacillus plantarum.Through the comparison of bacterial inhibition ability,the situation of selenium enrichment rate of strains and the optimization of culture conditions,the best effect selenium-enriched probiotic with 71.62% selenium enrichment rate was finally obtained as Lacticaseibacillus paracasei Se-19.2.Selenium-enriched probiotics treat mouse endometritis induced by E.coli.Compared with the control group,the E.coli group highly significantly up-regulated the m RNA and protein expression of pro-inflammatory factors IL-1β,IL-6 and TNF-α in mouse uterine tissue(P < 0.01),and significantly down-regulated the m RNA and protein expression of IL-10,ZO-1,and occludin(P < 0.05).Compared with the E.coli group,the effect of selenium treatment group and selenium + probiotic treatment group was not significant,and there was no significant change in the expression of each inflammatory factor and tight junction-related protein.After probiotic treatment,there was no significant change in IL-1β and IL-6,a significant decrease in TNF-α expression(P < 0.05),a highly significant increase in IL-10 expression(P < 0.01),and a significant increase in m RNA and protein expression of ZO-1 and occludin(P < 0.05).However,the expression of pro-inflammatory factors IL-1β,IL-6 and TNF-α were highly significantly decreased(P < 0.01),IL-10 expression was highly significantly increased(P < 0.01),and m RNA and protein expression of ZO-1 and occludin were significantly increased(P < 0.05)in the selenium-enriched probiotic-treated and antibiotic-treated groups.This result indicates that selenium-enriched probiotics improve the ability of probiotics themselves,inhibit the expression of inflammatory related factors,and improve the uterine barrier function.In this experiment,five strains of selenium-enriched probiotic bacteria were cultivated through selenium tolerance and selenium enrichment screening,among which,the highest selenium enrichment capacity was Lacticaseibacillus paracasei with 71.62%.It was applied to E.coli-induced endometritis in mice,and the results showed that the selenium-rich Lacticaseibacillus paracasei could improve the probiotic’s own ability to treat E.coli-induced endometritis in mice,reduce the inflammation and improve the uterine function.