Investigation on the probiotic characteristics of novel Lactobacillus acidophilus 2451 and its efficacy in preventing calf diarrhea

Lactobacilli are widely recognized for their beneficial effects on intestinal health. Here, we isolated a strain of Lactobacillus acidophilus (LA2451) from yogurt and systematically evaluated its probiotic potential. In vitro assessments demonstrated that LA2451 exhibited robust gastrointestinal tolerance, with a survival rate exceeding 50% at pH 2.0 and exceeding 45% in 0.1% bile salts. Furthermore, it exerted significant antimicrobial activity, producing inhibition zones of 15.0 ± 8.0 mm against E. coli and 15.0 ± 5.0 mm against Salmonella. In a pathogenic E. coli-induced calf diarrhea model, prophylactic administration of LA2451 significantly decreased the diarrhea rate to below 50% and mitigated colonic tissue injury. LA2451 intervention up-regulated the mRNA expression of intestinal tight junction proteins (P < 0.05), down-regulated key pro-inflammatory cytokines (P < 0.001), and elevated the anti-inflammatory cytokines (P < 0.01). Gut microbiota analysis via 16S rRNA sequencing revealed that LA2451 ameliorated intestinal dysbiosis, supporting it as a promising probiotic candidate.