Identification of Sarcina species in association with equine gastric glandular lesions. Sarcina identification in equine glandular gastric lesions

Background: The equine gastrointestinal microbiome is linked to many disease processes, but its role in the pathogenesis of equine glandular gastric disease (EGGD) is poorly understood.Objectives: To investigate whether the glandular gastric microbiota is altered in horses with EGGD, and whether EGGD lesions have a characteristic bacterial community profile.Study design: Prospective longitudinal studyMethods: Five Thoroughbred racehorses from one training centre underwent gastroscopy as part of poor performance investigation. Samples were taken from EGGD lesions and adjacent normal mucosa using guarded transendoscopic cytology brushes and frozen at -80 °C. DNA was extracted for 16S rRNA sequencing, and sequences compared against a database to generate taxonomic classification of the microbiota. The same horses, and additional animals, were sampled again six months later.Results: Normal glandular mucosal samples were characterised by a higher proportion of Proteobacteria (52 %) than EGGD lesions (21.7 %). Relative abundance of Firmicutes was lower in samples from normal mucosa (19.8 %) than from EGGD lesions (53.7 %). Linear discriminant analysis effect size (LEfSe) confirmed that a greater proportion of Firmicutes species was characteristic of samples collected from EGGD lesions. A very high relative abundance of Sarcina (up to 92.4 %) was associated with EGGD lesions in two horses. We were unable to comment on the stability of the glandular gastric microbiota over time.Main limitations: Small sample population. All horses examined had squamous or glandular gastric lesions; no horses had grossly normal gastric mucosa.Conclusions: There is evidence to suggest that the gastric microbiome is altered in horses with EGGD, although we are unable to demonstrate a causative effect. Sarcina was particularly increased in abundance in EGGD lesions and may be a useful biomarker of disease. Further investigation is necessary to determine the impact of alterations in the microbiome and the effect on gastric health.