Changes in gut bacterial communities in canaries infected by Macrorhabdus ornithogaster

Macrorhabdus ornithogaster is an opportunistic yeast that colonizes the gastric mucosa of many avian species. Until now, no studies have been focused on about the influence of a gastric infection on the balance of the intestinal microbiota of birds. In this study, 44 fecal samples from individual canaries, between six months and two years of age with and without M. ornithogaster infection, were analysed. The detection of the yeast was evaluated by 18S rRNA PCR. In order to evaluate the impact of the Macrorhabdus infection on the bacterial communities, the culture-independent methods by the use of amplicon based sequencing as well as 16S rDNA-DGGE were adopted. The different health status of animals affected the relative abundance of the main OTUs, with a greater diversification of the gut flora in healthy animals if compared to the infected. In particular, Lactococcus, Pseudomonas, Acinetobacter, Lachnospiraceae, Propionibacterium and Weissella were found to be characteristic of uninfected animals (FDR <0.05), while Lactobacillus and Candidatus Arthromitus were characteristic of infected animals (FDR <0.05). Both these taxa have been reported as immunostimulatory, involved in immunological disorders. In infected animals the inferred metagenome assessed by PICRUST clearly showed a positive correlation between the presence of M. ornithogaster and KEGG genesrelated to either lipid metabolism, already reported to be immunostimulatory by activation of macrophages and to play a pathophysiological role in several immunological disorders. Finally, our results show an interaction between infection of the digestive tract and intestinal microbiota of pet birds and provide insight about the changing of the complex enteric bacterial community.