Characteristics of the Intestinal Microorganisms in Middle-Aged and Elderly Patients: Effects of Smoking

[Image: see text] Introduction: Smoking affects the occurrence and development of many diseases. We attempt to study the structure of intestinal flora in the middle-aged and elderly population as well as how smoking affects the intestinal flora. Methods: We collected population information, biochemical indicators, and patient feces from 188 middle-aged and elderly male patients, and their feces were tested for the 16S rRNA gene of intestinal flora. Results: We performed a cluster analysis on the intestinal structure of the included population and found that there was a significant difference in the number of smokers between each group (p = 0.011). Subsequently, the microbiological diversity analysis of current smokers and nonsmokers was carried out. The results indicated that there was a significant difference in species composition between the two groups (p = 0.029). Through the analysis on LEfSe differential bacteria, it was found that in current smoking patients, the abundances of the genus Bifidobacterium and the genus Coprobacillus were less, while the abundances of the genera Shigella, Paraprevotella, Burkholderia, Sutterella, Megamonas, and p-75-a5 under the family level of Erysipelotrichaceae were slightly high. We analyzed the correlation between the abundances of these eight different bacteria and clinical indicators. The results revealed the following: the abundance of the genus Bifidobacterium was negatively correlated with fasting blood glucose (r = −0.198, p = 0.006) and positively correlated with uric acid (r = 0.207, p = 0.004) and total bilirubin (r = 0.175, p = 0.017); Shigella bacteria were positively correlated with fasting blood glucose (r = 0.160, p = 0.028) and uric acid (r = 0.153, p = 0.036) levels; the genus Paraprevotella and BMI (r = −0.172, p = 0.018) are negatively correlated; the abundance of the genus Burkholderia was positively correlated with γ-glutamyltransferase (r = 0.146, p = 0.045) levels; Sutterella was correlated with fasting blood glucose (r = 0.143, p = 0.05) and creatinine level (r = −0.16, p = 0.027), which was positively correlated with fasting blood glucose and negatively correlated with creatinine. Conclusions: In middle-aged and elderly patients with cardiovascular disease, smoking can reduce the abundance of Bifidobacterium, while the abundances of some negative bacteria such as Burkholderia, Sutterella, and Megamonas increase.