According to WHO, obesity comes in the fourth place as a death risk factor, after hypertension,
dietary risks and smoking. The influence of obesity and smoking on oral and gut microbiome -the
two largest microbial ecosystems in the human body- needs better understanding.
Using V3-V4 16S rRNA next-generation sequencing, we examined the orointestinal axis
microbiome of obese-smokers (ObSm), smokers, and healthy patients in addition to the
relationship between oral and gut bacteria. oral and gut microbiomes of ObSm and smokers had
higher diversity than healthy subjects and oral microbiomes were significantly more diverse than
gut microbiomes. The phyla Firmicutes and Proteobacteria were significantly more abundant in
the oral microbiome of healthy subjects than in ObSm and smokers, while the oral microbiome of
ObSm the phylum Bacteroidetes was significantly showed higher relative abundance.
Furthermore, Firmicutes was enriched in stool microbiome of smokers compared to ObSm and
healthy subjects, but the phylum Bacteroidetes was reduced in stool microbiome of ObSm
compared to smokers and healthy subjects. The phylum Proteobacteria was enriched in the stool
microbiome of ObSm than in smokers and healthy subjects at the genus level; Streptococcus,
Veillonella, and Prevotella were presented with higher relative abundance in the oral microbiome
of smokers than in ObSm and healthy subjects. interestingly, stool microbiome of ObSm and
smokers showed retracted representation of Bacteroides and Faecalibacterium in comparison to
healthy subjects.