Dietary probiotic Pediococcus acidilactici MA18/5M modulates the intestinal microbiota and stimulates intestinal immunity in rainbow trout (Oncorhynchus mykiss)

A study was conducted to evaluate the probiotic effect of Pediococcus acidilactici MA18/5M on rainbow trout, Oncorhynchus mykiss. Fish (310 +/- 9 g) were fed a control diet or a P. acidilactici-supplemented diet (at 2.4 x 10(6) CFU/g) for 4 weeks. The probiotic was observed to populate the intestine with levels ranging from log 3.7 to 5.4 CFU/g. Furthermore, these populations were able to persist for at least 24 hr after the cessation of probiotic feeding. High-throughput sequencing analysis of bacterial 16S rRNA libraries demonstrated that P. acidilactici was able to modulate the gut microbiome of rainbow trout and that the probiotic was detected as a common taxon on the mucosa and in the digesta of the probiotic fish (p < .05). Real-time polymerase chain reaction demonstrated that feeding the probiotic upregulated pro-inflammatory cytokines, interleukin-1 beta, and interleukin-8 and downregulated anti-inflammatory interleukin-10 compared to the control-fed fish. Furthermore, the mRNA levels for the mucosal antibody immunoglobulin T was also elevated in probiotic-fed fish. These findings help to explain some of the mechanisms behind the previously reported observed benefits of using this probiotic in the intestinal morphology and immunity of rainbow trout.