The effect of a synbiotic formula on the gut microbiota of broiler chickens and incidence on C. jejuni

Introduction. With the ban of dietary antimicrobial agents in animal farms, the use of probiotics, prebiotics or synbiotics to reduce pathogen load has attracted a great attention. In particular, Campylobacter jejuni has emerged as a leading bacterial cause of food-borne gastroenteritis in humans, mainly due to poultry food chain and poultry products. In a recent work a synbiotic mixture were administered for 15 days to young broilers and qPCR revealed an increase of the beneficial bacteria (i.e. bifidobacteria, lactobacilli) and a reduction of C. jejuni. In the current study the microbial gut community profiles and C. jejuni were evaluated in treated and untreated broilers by PCR-DGGE analysis to better understand the impact of the tested synbiotic product and support qPCR results. Methods. The synbiotic product was composed by the microencapsulated B. longum subsp. longum PCB133 (>109 UFC/g) and a galactooligosaccharide (3% w/w). It was administered to broilers for 15 days directly mixed to normal feed; faecal samples were collected three times along the trial (t0, t15, t20). DNA extracted from faecal samples was analyzed with DGGE technique after amplification with universal primers and with Campylobacter-specific primers (fla-DGGE). Obtained profiles analysed using the GelCompareII software package version 6.1 (Applied Maths, Kortrijk, Belgium). After normalization, a cluster analysis was performed using the Pearson similarity coefficient and unweighted pair group mathematical average (UPGMA) clustering algorithm. Results. DGGE profiles provided evidence that synbiotic consumption did not alter microbial profiles in the fecal microbiota of both untreated and treated animals; nevertheless a shift in the faecal microbiota of both groups was observed, due probably to animal growth and development. Moreover, DGGE results showed that the band corresponding to the administered probiotic strain PCB133 was detected in all treated animals and was persistent after the wash-out period. Preliminary fla-DGGE analysis underlined the effectiveness of the treatment on naturally infected animals. Discussion. The experimental study highlights the positive effect of the synbiotic approach in broiler chickens, confirming the efficacy of the probiotic PCB133 against C. jejuni without perturbation of gut microbial community.