Probiotic Pediococcus acidilactici modulates both localised intestinal- and peripheral-immunity in tilapia (Oreochromis niloticus)

Abstract

The application of probiotics in aquaculture has received concerted research efforts but the localised intestinal immunological response of fish to probiotic bacteria is poorly understood. Therefore, a study was conducted to evaluate the probiotic effect of Pediococcus acidilactici on Nile tilapia (Oreochromis niloticus) with specific emphasis on intestinal health and probiotic levels as well as system level responses such as growth performance, feed utilization and haemato-immunological parameters under non-challenged conditions. Fish (9.19 ± 0.04 g) were fed either a control diet or a P. acidilactici supplemented diet (at 2.81 × 10(6) CFU g(-)(1)) for six weeks. At the end of the study the probiotic was observed to populate the intestine, accounting for ca. 3% (1.59 × 10(5) CFU g(-)(1)) of the cultivable intestinal bacterial load. Real-time PCR indicated that the probiotic treatment may potentiate the immune-responsiveness of the intestine as up-regulation of the gene expression of the pro-inflammatory cytokine TNFα was observed in the probiotic fed fish (P < 0.05). Light microscopy observations revealed elevated intraepithelial leucocyte (IEL) levels in the intestine of P. acidilactici fed tilapia after six weeks (P < 0.05) of feeding and a trend towards elevated goblet cells was also observed after six weeks feeding (P = 0.08). Concomitantly at week six, along with elevated IELs and elevated TNFα mRNA levels in the intestine, an increased abundance of circulating neutrophils and monocytes were observed in fish fed the probiotic supplemented diet (P < 0.05). This haemopoietic expansion of innate immune cells could be reflective of an elevated state of immuno-readiness. Together these results suggest that the probiotic has a protective action on the intestinal mucosal cells, stimulating the innate immune response after feeding for a period of six weeks. These immunological modulations did not impair growth performance or the remaining haematological and zootechnical parameters compared to the control group (P > 0.05).

Modulation of the intestinal microbiota and morphology of tilapia, Oreochromis niloticus, following the application of a multi-species probiotic

“…Histological analysis revealed an increased population of IELs in the mid-intestine of tilapia after eight weeks feeding on the AquaStar ® Growout diet. Similar results have also been reported in tilapia fed monospecies probiotic applications of P. acidilactici (Standen et al 2013) or Lactobacillus rhamnosus (Pirarat et al 2011). Furthermore, after eight weeks, microvilli density was significantly higher in the mid-intestine of fish fed the probiotic when compared to control groups.…”

Research findings from the use of probiotics in tilapia aquaculture: A review

“…Other probiotic bacteria proven to bring benefits to tilapia include Aspergillus oryzae [32], Bifidobacterium bifiduim [29], Enterococcus faecium [34], Micrococcus luteus [14], Pediococcus acidilactici [35], P. fluorescens [24]. Streptococcus salivarius subsp.…”

“…Probiotics are, therefore, species specific for appropriate fish species. The normal microbial flora population, including beneficial varieties, in the digestive tract, may be killed or inhibited when exposed to oral chemotherapy [35]. This is particular pertinent in relation to tilapia, which, being an omnivorous fish species, contact a diverse range of bacteria in their environment.…”

“…Probiotic B. subtilis-supplemented diet at 5 Â 10 6 CFU g À1 benefited the innate immune system of Nile tilapia [31]. A Pediococcus acidilactici supplemented diet at 2.81 Â 10 6 CFU g À1 stimulated immune responses of Nile tilapia [35]. Supplement of P. fluorescens with diet at 10 8 CFU g À1 elevated growth performance and diseases resistance of Nile tilapia [24].…”

“…For instance, 15 [11] [32], 30 [23], 35 [28], 40 [34], 42 [35], 49 [18], 56 [19], 60 [27], 84 [15,31], 90 [14], 94 [57] days. The prolonged periods of time can be three months [38], or up to 8 months [33].…”