ABSTRACT: Little is known about the gastric mucosal microbiota in healthy horses, and its role in gastric disease has not been critically examined. The present study used a combination of 16SrRNA bacterial tag-encoded pyrosequencing (bTEFAP) and fluorescence in situ hybridization (FISH) to characterize the composition and spatial distribution of selected gastric mucosal microbiota of healthy horses. Biopsies of the squamous, glandular, antral, and any ulcerated mucosa were obtained from 6 healthy horses by gastroscopy and from 3 horses immediately post-mortem. Pyrosequencing was performed on biopsies from 6 of the horses and yielded 53,920 reads in total with 631-4345 reads in each region per horse. The microbiome segregated into two distinct clusters comprised of horses that were stabled, fed hay, and sampled at post-mortem (Cluster 1) and horses that were pastured on grass, fed hay, and biopsied gastroscopically after a 12-h fast (Cluster 2). The types of bacteria obtained from different anatomic regions clustered by horse rather than region. The dominant bacteria in Cluster 1 were Firmicutes (>83% reads/sample)-mainly Streptococcus spp., Lactobacillus spp. and Sarcina spp. Cluster 2 was more diverse, with predominantly Proteobacteria, Bacteroidetes and Firmicutes, consisting of Actinobacillus spp. Moraxella spp., Prevotella spp. and Porphyromonas spp. Helicobacter spp. sequences were not identified in any of 53,920 reads. FISH (n=9) revealed bacteria throughout the stomach in close apposition to the mucosa, with significantly more Streptococcus spp. present in the glandular region of the stomach. The equine stomach harbors an abundant and diverse mucosal microbiota that varies by individual.
Applied and Environmental Microbiology 01/2012; · 3.83 Impact Factor