Quantitative assessment of specific bacterial taxa of the intestinal microbiota of healthy and diarrheic horses.

BACKGROUND

Alterations in intestinal microbiota composition, as determined by DNA sequencing, are reported in horses with acute colitis compared with healthy horses.

HYPOTHESIS/

OBJECTIVES

Changes in specific bacterial populations can detect overall intestinal disruption of the normal intestinal microbiota. Identify bacterial taxa that indicate intestinal dysbiosis or health in horses using quantitative PCR (qPCR).

ANIMALS: Thirty horses with undifferentiated colitis, 13 with colitis associated with Salmonella spp., 14 with antibiotic-associated diarrhea (AAD), 52 healthy horses from Canada and 48 from the United States.

METHODS

This was a retrospective multicenter cross-sectional study. Horses were included in this study through a search of medical records of acute colitis cases, for which a fecal sample was collected. qPCR assays were developed for 14 bacterial taxa and compared using Welch t-test, one-way Analysis of Variance (ANOVA), Kruskal-Wallis or Welch's ANOVA.

RESULTS

qPCR analysis showed significant differences in absolute abundance in 7 out of the 14 bacterial taxa tested. Differences that were consistent across all colitis groups included higher abundance of Enterobacteriaceae (mean log10DNA ± SD; Control_Canada: 2.51 ± 0.53 vs undifferentiated: 3.43 ± 1.00; Control_USA: 2.06 ± 0.91 vs Salmonella spp.: 3.65 ± 1.05 and AAD: 4.22 ± 0.97, all P < .01) and Escherichia coli (2.28 ± 1.13 vs 3.54 ± 1.54; 1.80 ± 1.25 vs 3.74 ± 1.30 and 3.90 ± 1.52, all P < .01) and lower abundance of Turicibacter spp. (4.10 ± 0.24 vs 3.86 ± 0.37; 3.64 ± 0.27 vs 3.17 ± 0.30 and 2.96 ± 0.60, respectively; all P < .01).

CONCLUSIONS AND CLINICAL

IMPORTANCE

This study reports changes in bacterial taxa across various colitis phenotypes and indicates that this approach could serve as a faster, cost-effective proxy for detecting dysbiosis in the gastrointestinal tract of horses.