Probiotic Potential of M6 Isolated from Equines and Its Alleviating Effect on DSS-Induced Colitis in Mice.

Colitis in equines has high morbidity and mortality rates, which severely affects the development of the equine-breeding industry. With the issuance of antibiotic bans, there is an urgent need for healthier and more effective alternatives. In recent years, probiotics have been widely used as microbial feed additives in animal husbandry, playing a crucial role in preventing and treating diarrhea and regulating host immune function. In this study, we isolated and screened a strain with rapid and stable acid production using bromocresol purple, litmus milk coloration tests, and acid production performance assessments. Based on morphological characteristics, physiological and biochemical properties, and 16S rDNA identification, the strain was identified as and named M6. The M6 exhibited stable growth and tolerance to high temperatures, acid and bile salt concentrations, and simulated gastrointestinal fluid environments. The M6 strain demonstrated good antibacterial effects against , , and . The M6 strain did not produce hemolysis zones on Columbia blood agar plates, indicating its high safety, and was found to be insensitive to 12 antibiotics, including cephalexin and neomycin. Additionally, intervention in mice with dextran sulfate sodium (DSS)-induced colitis alleviated weight loss and shortened colon length. To a certain extent, it regulated the expression of inflammatory cytokines and the gut microbiota within the body and reduced inflammatory cell infiltration and intestinal barrier damage. In summary, the isolated M6 strain exhibited excellent probiotic properties and could alleviate DSS-induced colitis in mice, suggesting its potential application value as a probiotic in animal husbandry.