Abstract: Objective To investigate the characteristics of intestinal flora in newly diagnosed cases of colorectal cancer in Liyang City. Methods One hundred and fifty cases of newly diagnosed colorectal cancer （colorectal cancer group） and 150 healthy persons （control group） were selected, DNA was purified from fresh feces and amplified by polymerase chain reaction. 16S rDNA high-throughput sequencing was performed, fecal samples were inoculated in the culture medium for bacterial culture, and the bacterial community was identified and counted. Results Among the patients with colorectal cancer, 84 were males and 66 were females, aged 32-75 years old, with an average age of （56.88±8.74） years old. NM staging： 26 cases in stage Ⅰ, 94 cases in stage Ⅱ, 30 cases in stage Ⅲb. In the control group, there were 79 males and 71 females, aged 30-68 years old, with an average age of （56.73±8.28） years old. There was no significant difference in gender and age between the two groups （both P>0.05）. The results of 16S rDNA high-throughput sequencing showed that the Shannon index and Chao index in the colorectal cancer group was significantly lower than that in control group, the difference was statistically significant （both P<0.01）. The abundance of Firmicutes in colorectal cancer group was lower than that in control group, the abundance of Bacteroidetes, Proteobacteria, Clostridium and Actinomycetes was higher than that in control group, the difference was statistically significant （all P<0.01）. Bacterial culture results showed that the number of Escherichia coli, Enterococcus and Staphylococcus in the intestinal tract of colorectal cancer group was significantly higher than that of the control group, the number of Bifidobacterium, Lactobacillus, Peptococcus and Yeast was significantly lower than that of the control group, the difference was statistically significant （all P<0.01）. Conclusion The diversity of intestinal flora in newly diagnosed colorectal cancer patients is significantly lower than that in healthy people in Liyang City, the abundance of Firmicutes decreased, while the abundance of Bacteroidetes, Proteobacteria, Clostridium and Actinomycetes increased, the number of probiotics such as Bifidobacterium and Lactobacillus decreased, and the number of opportunistic pathogens such as Escherichia coli and Enterococcus increased.

Key words: Digestive system, Colorectal cancer, Intestinal flora