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].