The fact that changes in the intestinal microflora of UC patients are the major aetiology of UC is supported by an animal model of colitis. The UC-like colitis was not induced in bacterial-free conditions, but under the same condition, the colitis occured in the presence of bacteria in a UC patient [1, 2, 3, 4]. In contrast, fecal transplantation from healthy donors is expected to be effective in treating IBD patients [11, 12]. Accordingly, we became interested to evaluate a parameter of gut microbiota, which was highly related to the activity of UC and could predict the relapse of UC. With this in mind, in this study we used an NGS technique for fully analyzing the faecal bacteria. The summary of our investigation is as follows. We divided subjects into five subgroups, including active and quiescent (with or without mucosal inflammation) UC patients, UC patients’ consanguine and non-consanguine relatives. The latter two groups were non-IBD control groups. One is relatives with blood relationship with the UC groups, the another is relatives without blood relationship. We obtained faecal samples from all subjects and analyzed intestinal microbiota using NGS. Significant difference was calculated in 18 Species, 10 Genera, and 4 Families.
Hitherto, there have been reports on certain bacteria being increased or decreased in active UC patients compared with healthy, non-IBD individuals [13, 14, 15]. However, to our knowledge, this is the first report of so many different bacterial strains being revealed upon analysis of faecal samples. We believe that there is a need for further studies to fully understand how different bacterial species are contributing to the aetiology, exacerbation or have curative effect in IBD. Indeed, the knowledge from microbiota studies in IBD patients has led to faecal microbiota transplantation (FMT) using healthy, non-IBD individuals as donors [16]. However, this is not to say that faecal sample from every non-IBD individual is suitable for FMT because of a large variation in mirobiota among healthy donors [16]. Therefore, during the present endeavour, we focused on the analysis of the faecal microbiota by applying the NGS technique [9, 10] in UC patients and their relatives aiming to obtain clinically relevant understanding on the diversity of the bacteria in patients with UC and non-IBD individuals. We thought that potentially, NGS analysis of bacteria in fecal samples of UC patients could lead to the development of biomarkers for understanding the condition of UC. Ideally, we thought that such biomarkers could predict the severity of UC and the potential for future flare-up. Hence, with the NGS technique, we undertook a quantitative Discriminant analyses of faecal microbiota in UC patients and the patients’ relatives. The diversity of Bacteroides Genus was found to be higher in group V, but the quantity of this Genus was higher in group I. Similarly, Bacteroides fragilis was increased in group I, while the other varieties were increased in group V, reflecting an increase in the amount of Bacteroides fragilis. Therefore, in active UC, the amount of Bacteroides fragilis was increased, but the diversity of Bacteroides Genus was decreased. On the contrary, in healthy control group, the amount of Bacteroides fragilis was decreased, but the diversity of Bacteroides Genus was increased (Fig. 6). Therefore, the quantity of Bacteroides fragilis should be a relevant measurement in predicting UC flare-up in clinical practice setting. These observations might be very relevant in understanding UC activity profile (reflected in Tables 1, Figs. 5 and 6). Regarding Family Gemella incertae_sedis and Clostridiales Family XI. Incertae Sedis, these showed an increased diversity in group I. The same trend was shown by the Genus Anaerococcus, Finegoldia and Peptoniphilus and Species Anaerococcus vaginalis, Finegoldia magna and Peptoniphilus gorbachii (seen in Table 1, and Fig. 4). Therefore, one may assume that these group of bacteria are significant factors in UC flare ups.
The Discriminant analysis was performed on the data obtained as quantitative approach based on the mathematical model above. Then we thought that it might be logical to apply the Discriminant analysis, together with a mathematical model. Compared among the five groups, the Ds value was smallest in group I with active UC and greatest in group V, healthy individuals without blood relationship to UC patients. In the analysis, significant difference was calculated between group I and group V. We also looked for any likely difference between group I and group V in Principal component analysis, which supported the outcome of the Ds analysis. Furthermore, this parameter may be a clinical biomarker of UC activity, since the Ds values are obtained from analysis of the intestinal microflora and selected bacterial quantity.
Our analyses show that 18 Species and 10 Genera might be the key bacteria to consider in the evaluation of gut microflora in UC. As far as we know, this is the first attempt of the NGS and Ds to the study of microbiota in UC patients, consanguine and non-consanguine relatives.
As mentioned above, we found that the amount of Bacteroides, its diversity and the balance with Bacteroides fragilis are relevant factors in UC activity profile. There are some reports that Bacteroides Genus and Bacteroides fragilis can affect UC activity, but at present, there is lack of knowledge. Accordingly, we believe that Bacteroides fragilis are related to UC activity, but the diversity of Bacteroides Genus is part of a balanced microbiota homeostasis [14, 15, 16, 17, 18]. The differences of diversity have been reported in some studies. Some studies reported the diversity is reduced in active UC patients [19, 20]. Thus the biodiversity of the microbiome may be important in considering a balanced condition. In addition, the balance of Clostridiales Family XI. Incertae Sedis might also be a key point. Anaerococcus, Finegoldia and Peptoniphilus belong to Clostridiales Family XI. Incertae cedis that are Gram positive anaerobic cocci. They are indigenous bacteria, and exist in the intestinal tract, skin and the birth canal, and other sites [21, 22, 23]. We found that these bacteria are also prevalent in patients with active UC.
Akkermansia was increased in group V in both quantity and diversity, but this strain of bacteria has been reported to be a factor in IBD flare ups [24, 25, 26]. Therefore, it would appear that our observations contradict the hitherto reports on Akkermansia. Thus, several strains of bacteria may be involved in the clinical manifestation of UC profile. The 18 Species and 10 Genera mentioned above may also be clinically relevant candidates in understanding UC profile. Although, the quantity and the diversity of bacteria are important, the bacterial functions are also thought to be important as well in understanding the role of microflora in disease pathogenesis. In this study, we did not evaluate these bacterial functions, but in the future, it will be necessary that we have a keen focus on bacterial functions.
Understanding the factors closely associated with the onset and exacerbation of UC should enable us to better manage this disorder. In this study, our major endeavour was to thoroughly investigate the role of intestinal microbiota in the pathogenesis of UC and establish a simple and reliable model. The Ds is required to be appropriate for assessing the clinical status of UC patients and determining treatment strategies. It was thought that in patients diagnosed with UC, high Ds value could mean stable remission and vice versa. We also noticed that low Ds value may be associated with UC relapses, predictions of exacerbations, and severity.