The Effects of Ageing on the Colonic Bacterial Microflora in Adults

Background: The composition of the fecal mircoflora and its changes on ageing have rarely been investigated in large samples of both patients and volunteers. Methods: We analysed the fecal flora by conventional microbiological testing (Kyberstatus(R), Institute of Microecology, Herborn, Germany) of stool samples from 35292 adults (age: 46.3 +/- 0.08 [18 to 96] years, 9564 males, 24784 females; remaining=missing data) with different intestinal and non-intestinal diagnoses for total colony-forming units (CFU) (per g stool) as well as relative abundance of Bifidobactetia, Bacteroides spp., Escherichia coli, Enterococcus spp., and Lactobacillus spp. with respect to age, gender, and clinical data available (e.g., stool consistency and pH). Results: The total CFU was stable and showed no age- or gender-related changes. Individual bacterial species constantly and significantly increased with age (E. coli, Enterococci spp.), or decreased at higher age (Bacteroides spp.), or were stable throughout the life span (Lactobacilli, Bifidobacteria). Gastrointestinal diagnoses (Crohn's disease, n = 198; ulcerative colitis, n = 515; irritable bowel syndrome, n = 7765; other GI diagnoses, n = 10478) tended to exhibit some specificity of the bacterial profile, and when GI diagnoses were excluded, the age-related bacterial profile of the remaining group (n = 15 619, m:f = 4197:11422) was not different. Conclusion: Conventional microbiological investigations of the fecal microbiota showed both bacteria-specific as well as a general pattern of ageing of the colonic microbiota, with the last decades (more than 60 years) demonstrating the most profound changes. It remains to be shown whether these changes reflect direct changes of the gut microbiota, the mucosal innate immunity, or indirect consequences of age-related altered nutrition.