Probiotic Potential and Characterization of Enterococcus faecium Strains Isolated from Camel Milk: Implications for Animal Health and Dairy Products

In this study, 62 lactic acid bacteria (LAB) strains were isolated from raw camel milk and evaluated for their probiotic potential. The strains exhibited significant variability in their ability to withstand simulated gastrointestinal conditions. Of the isolates, only 26 survived exposure to pH 2, and just 10 were tolerant to 0.3% bile salts. Partial sequencing of the 16S rRNA gene identified all the strains as belonging to the species Enterococcus faecium. Several probiotic traits were assessed, including adhesion to gastric mucin and STC-1 intestinal epithelial cells, as well as auto-aggregation and co-aggregation capacities. Although adhesion to hydrophobic solvents such as chloroform and ethyl acetate was generally low to moderate, all the strains demonstrated strong adhesion to gastric mucin, exceeding 60% at all the growth stages. Notably, two strains—SCC1-33 and SLch6—showed particularly high adhesion to STC-1 cells, with values of 7.8 × 103 and 4.2 × 103 CFU/mL, respectively. The strains also exhibited promising aggregation properties, with auto-aggregation and co-aggregation ranging between 33.10% and 63.10%. Furthermore, all the isolates displayed antagonistic activity against Listeria innocua, Micrococcus luteus, and Escherichia coli. Cytotoxicity assays confirmed that none of the tested strains had harmful effects on STC-1 cells, indicating their safety and supporting their potential application as probiotics.