THE mammalian gastrointestinal
(GI) tract is home to a complex
ecosystem of micro-organisms
(bacteria, fungi, protozoa, archaea
and viruses) known as the
micro flora.
The total microbial load in the
intestine is estimated to range between
1012 to 1014 organisms, about 10 times
the number
of cells
composing
the host
body. In
the non-
diseased
state, the
micro flora is
responsible for regulating host health
by:
- Aiding digestive processes
– Deamination and fermentation of
amino acids
– Carbohydrate fermentation
– Deconjugation of bile acids
– Vitamin synthesis - Competitive exclusion of non-
resident bacteria
– Competition for oxygen, nutrients,
mucosal adhesion sites
– Micro-environment changes –
secretion of anti-microbial substances,
alterations in gut pH - Modulating the immune system
– Stimulates gut-associated lymphoid
tissue (GALT)
– Increase concentrations of
immunoglobulins (Ig) - Maintaining mucosal barrier function
– Bacterial fermentation produces
short-chain fatty acids (SCFAs) which
promote epithelial cell growth
– Increase mucus production.
Bacteria levels in the intestines are
regulated by host control mechanisms
which include intestinal motility and
antimicrobial substances in pancreatic
and biliary secretions.
Disruption of these regulatory
measures can result in an imbalance
in the resident intestinal micro ora,
known as intestinal dysbiosis, which may develop due to colonisation with
transient pathogens or an overgrowth
by opportunistic resident bacterial
species.
Intestinal dysbiosis can lead to
various mechanisms that negatively
affect the functioning of the GI
tract; these include dehydroxylation
of fatty acids leading to impaired
fat absorption, increased intestinal
permeability, destruction of brush
border enzymes and competition for
substrates leading to nutrient and
vitamin malabsorption.
Inflammatory Bowel Disease (IBD)
is thought to involve an abnormal
interaction between commensal
intestinal micro ora and the intestinal
immune system in genetically
predisposed individuals.
It is suspected that intestinal
inflammation causes a dysbiosis
towards Gram-negative bacteria and
a depletion of commensal bacteria
leading to a reduced capability of
the micro ora to down-regulate an
aberrant immune response.
Recent molecular studies
performed in dogs and cats
have revealed differences in the
intestinal micro ora between
healthy animals and IBD patients.
Animals with IBD have increased
levels of Enterobacteriaceae and
Proteobacteria with reduced levels of
Bacteriodales and Clostridiales and an
overall reduction in bacterial species
richness.
The term probiotic is used to
describe a live micro-organism which,
when administered in adequate
amounts, confers a health benefit on the host. These health effects are
thought to be due to a direct inhibition
of pathogenic micro-organism
colonisation or by immune-enhancing
effects on gut-associated lymphoid
tissue and increasing immune-
modulating cytokines.
Within the European Union the only
probiotic authorised for use in canine
and feline species by the European
Foods Standards Agency (EFSA) is
Enterococcus faecium NCIMB 10415. This
strain has been extensively researched
to verify its safety and efficacy in dogs
and cats; these studies demonstrate the following benefits from using the
strain:
- Reduced faecal levels of Clostridium
spp in dogs and cats - Reducef adhesion of Clostridium
perfringens to intestinal mucosa by 70% - Increased faecal levels of beneficial Bi dobacteria spp and Lactobacilli spp
- Maintained faecal microbial diversity in cats subject to stressful situations, while the placebo group had a reduction in the micro oral diversity
- Reduced morbidity associated with chronic feline herpesvirus-1 infection
- Increased faecal and plasma IgA in young dogs
- Improved response to canine distemper virus vaccination as evidenced by higher specific IgG and
IgA15
Quicker resolution
Probiotics are commonly
recommended as an ancillary treatment
for various GI disorders. The use of
probiotic products in acute diarrhoea
is well established and studies have
demonstrated a quicker resolution of
diarrhoea in dogs and cats when
using probiotics.
A combination of Enterococcus faecium
and prebiotic (Synbiotic DC, Protexin
Veterinary) has been investigated for its
ability to prevent diarrhoea in dogs in a
rehoming shelter.
In a double-blinded, placebo-
controlled, randomised study 81 dogs
were randomly assigned to receive
either the placebo or Synbiotic, and the
incidence of diarrhoea was recorded.
Dogs receiving the Synbiotic were 50%
less likely to develop diarrhoea than
those receiving the placebo.
There is limited information
regarding the use of probiotics in
chronic diarrhoea although work
has been completed looking at a
combination of probiotics, prebiotics,
alpha-glucan and beta-glucan (Protexin
Pro-Kolin Enterogenic) in cats
naturally infected with the protozoal
parasite, Tritrichomonas foetus.
This
prospective double-blinded, placebo-
controlled trial demonstrated that the cats treated with the product had
a higher resolution rate and reduced
relapse rate compared to placebo. The
relapse rate in the placebo group was
61.5% versus 15.4% in the treatment
group (P = 0.021).
The use of probiotics in veterinary
practice is well established with many
clinicians opting to utilise them in
acute diarrhoea cases in dogs and cats.
In chronic diarrhoea, the disturbances
to the intestinal micro ora are well
documented but further work is
needed to understand these changes
fully.
Future studies will need to
investigate the effects probiotics can
have on the disrupted micro ora and
any potential role they may have in
the management of chronic diarrhoea
patients.
One area of research showing
promise in human medicine is the
utilisation of faecal transplantation,
and while there are reports of
promising results in canine patients,
controlled clinical trials are needed
before this can be advocated as a viable
treatment option.
1. Suchodolski, J. (2011) Companion animals
symposium: microbes and gastrointestinal health
of dogs and cats. J Anim Sci 89: 1,520-1,530.
2. Rutgers, H. et al (1993) Bacterial overgrowth in
dogs with chronic intestinal disease. J Vet Intern
Med 7: 133-135.
3. Packey, C. and Sartor, R. (2009) Commensal
bacteria, traditional and opportunistic pathogens,
dysbiosis and bacterial killing in inflammatory
bowel disease. Curr Opin Infect Dis 22: 292-301.
