Probiotic potential and immunomodulatory properties in Enterococcus faecium GMB24 and Enterococcus hirae SMB16...

Probiotic attributes of lactic acid bacteria isolated from goat and sheep milk samples were analysed by culturing them on an MRS agar medium. The most potential isolates, GMB24 and SMB16, were identified by biochemical tests which had ability to tolerate different concentrations of acid and bile and phenol resistance. They were further identified as Enterococcus faecium GMB24 and Enterococcus hirae SMB16 by 16S rRNA gene sequencing approach. The probiotic potential of the isolates GMB24 and SMB16 were recorded including antimicrobial activity against pathogenic bacteria viz., Escherichia coli (MTCC118), Staphylococcus aureus (MTCC7443), Pseudomonas aeruginosa (MTCC424), Listeria monocytogens (MTCC657) and Salmonella typhimurium (MTCC733), and antibiotic susceptibility test. The isolates SMB16 and GMB24 exhibited a higher zone of inhibition against P. aeruginosa (19.00 ± 0.57 mm) and S. aureus (25.66 ± 0.88 mm), respectively. The data from these experiments were used for the principal component analysis (PCA) to assess the survivability of the isolates under different factors. The heatmap generated in this study clustered the bacterial isolates based on their phenotype properties. Further, immunomodulating activities of these probiotic bacteria were tested on neutrophil adhesion test, haemagglutinating antibody titer and delayed-type hypersensitivity. Probiotic E. faecium GMB24 and E. hirae SMB16, at 10⁹ cells/mL doses per day, increased the neutrophil adhesion, haemagglutinating antibody titer and DTH in comparison to the untreated control group. The isolates showed negative test for haemolytic and gelatinase activities and hence were considered safe. E. faecium GMB24 and E. hirae SMB16 were shown to have high probiotic potential and immune-stimulant action.