1. Species richness for antibiotic group
Days
ObservedSpecies
0 7 14 28 42
0
500
1000
1500
a
b b
a a
The effect of Purina HA Hydrolyzed™ diet and
antibiotics on the fecal microbiome in healthy dogs
AB Blake, BC Guard, JM Steiner, JS Suchodolski, FP Gaschen, E Olsen
Gastrointestinal Laboratory, Texas A&M University, College Station, TX, USA
Gastrointestinal disease in dogs is generally characterized by a state of dysbiosis—
an imbalance in the gut microbiome.1 Therapeutic intervention for acute or chronic
gastrointestinal disease in dogs includes dietary trials, antimicrobials, and/or
steroids.2 To date, the effect of diet alone on the canine gastrointestinal
microbiome has not been fully elucidated. Purina HA Hydrolyzed™ diet is commonly
recommended by veterinarians for dogs with gastrointestinal problems because it
can act as a novel carbohydrate and protein source and is hypoallergenic.
Metronidazole is an antibiotic often prescribed for dogs with gastrointestinal
problems because it acts against anaerobic pathogens and can be used as an anti-
diarrheal, however, its direct effects on the fecal microbiome have not been fully
characterized. Therefore, the aim of this study was to evaluate the effect of Purina
HA diet and metronidazole on the fecal microbiome of healthy dogs.
Introduction Results
Objective
 Evaluate the effect of Purina HA diet as well as metronidazole
administration on the fecal microbiome of healthy dogs
Materials and Methods
 24 healthy pet dogs on a variety of maintenance diets were enrolled
 Control group (n=8) remained on their original diet
 Dietary group (n=8) were switched to a Purina HA diet
 Antibiotic group (n=8) were administered metronidazole for
two weeks
 Fecal samples were collected at baseline (day 0), and days 7, 21, and 42
for the control and dietary group, and at days 0, 7, 14, 28, and 42 for the
antibiotic group
 Fecal DNA isolation performed (MOBIO- PowerSoil® DNA
Isolation Kit)
 Fecal microbiota was analyzed by:
 Illumina sequencing of the 16S rRNA gene
 19,200 sequences per sample (QIIME v1.7)
 Data was tested for normality using the Shapiro-Wilk test
 Bacterial abundances and alpha diversity measures between groups were
compared using a non-parametric Friedman’s test for repeated measures
followed by a Dunn’s post-test
 Analysis of similarities (ANOSIM) was used to compare microbial
communities
 P-values were adjusted for multiple comparisons where appropriate using
the Benjamini & Hochberg false discovery rate
Results
Results
1. Markel ME, et al. (2012) Characterization of fecal dysbiosis in dogs with chronic
enteropathies and acute hemorrhagic diarrhea. Journal of veterinary internal medicine
26(3):765-766.
2. Suchodolski JS, et al. (2012) The Fecal Microbiome in Dogs with Acute Diarrhea and
Idiopathic Inflammatory Bowel Disease. PLoS ONE 7(12): e51907.
doi:10.1371/journal.pone.0051907
Discussion and Conclusion
References
 PCoA plots showed no clustering of microbial communities between time
points in the control group nor dietary group (ANOSIM; p>0.05). (Figure 1
and Figure 2)
 Microbial communities were significantly different based on clustering
between time points on metronidazole v. off metronidazole (ANOSIM;
p<0.05). (Figure 4)
 Species richness decreased during metronidazole treatment (p<0.0001).
(Figure 5)
 Taxonomic groups were not significantly different between time points in
the control group nor in the dietary group (p>0.05). (Figure 3)
Proteobacteria, Firmicutes, Fusobacteria, and Bacteroidia were all
significantly altered during periods of metronidazole administration
(p<0.05). (Figure 6)
 Treatment of healthy dogs with Purina HA diet did not cause a significant
shift in microbial communities, species richness, or taxonomic abundance
between time points
 Treatment of healthy dogs with metronidazole caused significant shifts in
the microbial community and an overall decrease in species diversity
 Obligate anaerobic bacteria including Fusobacteria, Clostridia
and Bacteroidia decreased
 Facultative anaerobic bacteria including Enterobacteriaceae
and Streptococcus increased
 Four weeks after antibiotic treatment, the microbial content had not
returned to baseline (day 0)
 Future studies are needed to examine the long term effects of antibiotic
treatment on dogs with acute or chronic gastrointestinal disease and any
subsequent repercussions for the microbiome
The authors have no conflicts of interest to disclose.
Amanda Blake
Student Assistant Research
Gastrointestinal Laboratory
amandablake@tamu.edu
Disclosure
Figure 4 (Above). Principal Coordinate Analysis (PCoA) of unweighted
UniFrac distances of 16S rRNA genes for antibiotic group. Green circle
indicates time points off metronidazole and red circle indicates time points on
metronidazole. (ANOSIM; p<0.05)
Figure 6 (Above). Profile of taxonomic abundance over time for antibiotic
group.
Key
Day 0
Day 7
Day 14
Day 28
Day 42
Key
Day 0
Day 7
Day 21
Day 42
Figure 1 (Right). Principal
Coordinate Analysis (PCoA) of
unweighted UniFrac distances
of 16S rRNA genes for control
group. (ANOSIM; p>0.05 for all
comparisons)
Key
Day 0
Day 7
Day 21
Day 42
Figure 2 (Left). Principal Coordinate
analysis (PCoA) of unweighted
UniFrac distances of 16S rRNA genes
for dietary group. (ANOSIM; p>0.05
for all comparisons)
Figure 5 (Above). Species richness for the antibiotic group. Red indicates time
points on metronidazole. (Friedman’s; p<0.0001) Groups not sharing a common
letter are significantly different from one another. (Dunn’s; p<0.05)
Figure 3 (Above). Profile of taxonomic abundance over time for control group.
(q>0.05 for all bacterial groups)
Control Group Antibiotic Group