Effect of oral administration of omeprazole on the microbiota of the gastric glandular mucosa and feces of healthy horses

Background
Proton pump inhibitors, such as omeprazole, are used extensively in both human and veterinary patients for treatment and prevention of gastric ulcer syndrome. In human and companion animal medicine, omeprazole administration has been associated to shifts in gastric and fecal microbiota and increased incidence of Clostridioides difficile enterocolitis, especially in prolonged treatments.
Hypothesis/Objectives
The purpose of this study was to assess the effect of omeprazole on gastric glandular and fecal microbiota in healthy adult horses.
Animals
Eight healthy research horses stabled on straw and fed 100% haylage.
Methods
Prospective controlled study. Transendoscopic gastric glandular biopsies and gastric fluid as well as fresh fecal samples were obtained from each horse at a 7-day interval without treatment to serve as controls. Samples were taken on the same horses before and after a 7-day treatment with omeprazole (4mg/kg PO q24h). Fluid pH was immediately assessed and the rest of samples were kept frozen at -20°C until analysis. Bacterial taxonomy profiling
was obtained by V1V3 16S amplicon sequencing from feces and gastric glandular biopsies. Analysis of alpha, beta diversity and comparison between time points were performed with MOTHUR and results were considered significant when p<0.05.
Results
Significant structural diversity in the microbiota was found in the glandular gastric samples after 7 days of omeprazole administration. No significant differences were found in composition and diversity of fecal microbiota.
Conclusions and clinical importance
A short course of oral omeprazole does not modify fecal microbiota in healthy horses but modifies the structure of gastric glandular microbiota