Lakhasly

Another important area of study is the relationship be- tween stress, microbiota, and behaviour [9,10].Recently, evidence supporting this suggestion was provided by a clinical study that observed elevated serum levels of IgM and IgA against the lipopolysaccharide (LPS) of gut commen- sals in patients with depressionUsing a mouse model of induced anxiety and depression via olfactory bulbectomy, investigators showed that elevated corticotropin-releasing hormone (CRH) expression, increased c-Fos activity, serotonin levels, and colon moti- lity were associated with an altered intestinal microbiome [11], which was suggested to be due to the activation of the hypothalamic pituitary adrenal (HPA) axis [11].The addition of rifaximin treat- ment in stressed rats significantly decreased the total bacterial load, altered the microbial community leading to a dominance of Lactobacilli, and prevented the increase of gut permeability induced by the stress trials, a finding that suggests the antibiotic protects intestinal barrier function by modulation of the gut microbiome [14].Analysis of the composition of luminal bacteria using fluorescence in situ hybridization revealed that stress alone resulted in a loss of Verrucobacteria, a twofold increase in Clostridium spp., and the added pre- sence of a low abundance population of Lactobacillus/ Enterococcus spp.and significant increases in Verrucobacteria, Enterobacteria, and Lacto- bacillus/Enterococcus spp.population.[12].

Another important area of study is the relationship be-
tween stress, microbiota, and behaviour [9,10]. Using a
mouse model of induced anxiety and depression via
olfactory bulbectomy, investigators showed that elevated
corticotropin-releasing hormone (CRH) expression,
increased c-Fos activity, serotonin levels, and colon moti-
lity were associated with an altered intestinal microbiome
[11], which was suggested to be due to the activation of the hypothalamic pituitary adrenal (HPA) axis [11]. In a
different study that compared the effect of stress and/or
antibiotics on the gut microbiome of mice, antibiotics
were found to lower overall bacterial counts as expected,
and with the addition of stress via the water avoidance
stress test, a further reduction in the bacterial load was
observed [12]. Analysis of the composition of luminal
bacteria using fluorescence in situ hybridization revealed
that stress alone resulted in a loss of Verrucobacteria, a
twofold increase in Clostridium spp., and the added pre-
sence of a low abundance population of Lactobacillus/
Enterococcus spp. Antibiotics alone similarly reduced Ver-
rucobacteria but also reduced Clostridium spp. and sig-
nificantly increased Enterobacteria and the Lactobacillus/
Enterococcus spp. population. The combination of stress
and antibiotics created yet another novel environment
with a sixfold reduction in Clostridium spp. and significant
increases in Verrucobacteria, Enterobacteria, and Lacto-
bacillus/Enterococcus spp. [12]. The study highlights the
dynamic nature of how host–microbiota interactions and
stress may modulate microbiome profiles [12].In a related
report from the same research group, changes in the
expression of gut sensory markers were shown to be
associated with changes in Bacteroides spp., Lactobacillus
spp., and Bifidobacterium spp., however changes in gut
microbiota composition did not alter expression of toll-
like receptors [13]. A similar stress and antibiotic study in
rats also identified a decrease in overall bacterial diversity
in distal ileum of the chronic stress group compared to the
control group, with no accompanying difference in the
overall bacterial load, and this dysbiosis was characterized
by the reduction of less-abundant members of the bac-
terial community [14]. The addition of rifaximin treat-
ment in stressed rats significantly decreased the total
bacterial load, altered the microbial community leading
to a dominance of Lactobacilli, and prevented the
increase of gut permeability induced by the stress trials,
a finding that suggests the antibiotic protects intestinal
barrier function by modulation of the gut microbiome
[14].
In a clinical study focused on further exploration of the
link between microbiota composition and depression,
researchers observed a general underrepresentation of
the Bacteroidetes phylum in depressed patients and an
association of the Lachnospiraceae family with the
depression group, and interestingly, even with a decrease
in Bacteroidetes, specific operational taxonomic units
(OTUs) identified as members of the Bacteroidetes phy-
lum correlated with depression [15]. It has been
suggested that increased gut permeability and related
bacteria translocation may contribute to increased inflam-
mation in depressed individuals [16]. Recently, evidence
supporting this suggestion was provided by a clinical
study that observed elevated serum levels of IgM and
IgA against the lipopolysaccharide (LPS) of gut commen-
sals in patients with depression