Investigation phylogenetic groups distribution of commensal Escherichia coli strains of people with colorectal cancer and healthy people

Background and Aim : Colorectal cancer or CRC, is the third-most common cancer in the world. Escherichia coli is one of the components of gut microbiota, which approved that in comparison with healthy people, it,s population is increased in people's gut with CRC. pathogenic E. coli strains fall into phylogenetic group B۲ or D which have a type of virulence factor and most E.coli strains that isolated from the patients with CRC, belonged B۲ phylogenetic group, Therefore it can be considered as a risk factor for the development of CRC. The aim of this study was the distribution of phylogenetic groups distribution of E. coli strains which isolated from patients with CRC and healthy people.Methods : In this study from ۷۰ stool samples ( ۵۰ normal and ۲۰ patients with colorectal cancer), E. coli strains were isolated and cultured. PCR was performed with a standard protocol. In isolates related to the B۲ phylogenetic group, chuA and also yja genes are positive but in D phylogenetic group yja gene is negative. In B۱ and A phylogenetic groups, the chuA gene is negative; however TSEP۴C۲ DNA fragment in B۱ exists but A phylogenetic group has not this fragment of DNA.Results : From ۲۰ E. coli strains of patients ۱۱(۵۵%), ۷ (۳۵%), ۰ and ۲ (۱۰%) were related to B۲, D, B۱, and A phylogenetic groups respectively.Conclusion : Phylogenetic analyses have shown that most of the E.coli strains isolated from patients fall into the B۲ phylogenetic group significantly.

Keywords:

Colorectal cancer , Escherichia coli , A , B۱ , B۲ , and D phylogenetic groups