Fusobacterium nucleatum and Bacteroides fragilis detection in colorectal tumours: Optimal target site and correlation with total bacterial load

Background Mucosal infiltration by certain bacterial species may contribute to the development and progression of colorectal cancer (CRC). There is considerable variation in reported detection rates in human CRC samples and the extent to which bacterial infiltration varies across regions of the primary tumour is unknown. This study aimed to determine if there is an optimal site for bacterial detection within CRC tumours. Methods Presence of target bacterial species was assessed by quantitative real-time PCR (qPCR) in 42 human CRC tumours. Abundance in primary tumour regions, normal epithelium and at metastatic sites was investigated in an expanded cohort of 51 patients. Species presence/absence was confirmed by diversity profiling in five patients. Correlation with total bacterial load and clinicopathological features was assessed. Results Fusobacterium nucleatum and Bacteroides fragilis were detected in tumours from 43% and 24% of patients, respectively (17% positive for both species). The optimal detection site was the tumour luminal surface (TLS). Patients testing positive at the TLS frequently tested negative at other sites, including central tumour and invasive margin. F. nucleatum was detected at a higher frequency in tumour versus normal epithelium (p < 0.01) and was associated with more advanced disease (p = 0.01). Detection of both species correlated with total bacterial load. However, corroboration of qPCR results via diversity profiling suggests detection of these species may indicate a specific microbial signature. Conclusions This study supports a role for F. nucleatum in CRC development. Presence of F. nucleatum and B. fragilis varies across primary tumour regions, with the TLS representing the optimal site for bacterial detection.

Protective effects of Bacteroides fragilis against lipopolysaccharide-induced systematic inflammation and their potential functional genes

Bacteroides fragilis, one of the potential next generation of probiotics, has been demonstrated to alleviate inflammation-associated diseases. In this study, we compare the anti-inflammatory effects of six Bacteroides fragilis strains...

Gender assessment of the gut microbiome in obese patients

The aim. To assess the relationship between body mass index (BMI) and gut bacteria in men and women with obesity.Materials and methods. The study included 56 overweight patients, divided into 2 groups. The first group consisted of 27 women (the average age was 62 ± 2.2 years), the second group — 29 men (the average age was 55 ± 9 years). The Quetelet index (kg / m2) was calculated for all patients. To study the gut microbiome, the method of polymerase chain reaction in real time (RT-PCR) and metagenomic sequencing were used. DNA from feces was isolated using the Express-DNA-Bio DNA isolation kit (AlkorBio, Russia). To carry out RT-PCR, a set of reagents “Colonoflor-16” (“Alfalab”, Russia) was used. For microbiome sequencing, DNA libraries were prepared using the Illumina Nextera Sample Preparation Kit with DNA primers corresponding to the V3 — V4 regions of the 16S rRNA gene. The study of fecal samples was carried out using 16S rRNA gene sequencing on the Illumina platform (MiSeq sequencer).Results. It was revealed that a higher total number of bacteria, an increased content of Bacteroides fragilis group and Faeca-libacterium prausnitzii, is statistically significantly more common in women than in men. Strong negative correlations were found between BMI and total bacterial mass, between BMI and the number of Bacteroides fragilis group among women with grade I obesity. In overweight men, a correlation was found between BMI and the Bacteroides fragilis group / Faecalibacterium prausnitzii ratio.Conclusions. The total number of bacteria, the content of Bacteroides fragilis group and Faecalibacterium prausnitzii in the gut of patients have statistically significant associations with BMI, and probably can affect the formation of metabolic disorders to a greater extent in women than in men. To clarify the identified trends and patterns in this pilot study, further study of the microbiome with a large number of patients and additional analyzes of the metagenome (16S rRNA) and metabolome, a transcriptome, allowing to control the expression of key metabolic enzymes, largely associated with the compositional features of the gut microbiocenosis, is required.

The features of the composition of the gut microbiota in patients with hypertension and abdominal obesity

The aim of this work was to study the features of the composition of the gut microbiota (GM) in patients with arterial hypertension (AH), which occurs against the background of abdominal obesity (AO). Materials and methods. The paper presents the data on examination of 70 patients with AH of 2–3 degrees (46 patients with AO and 24 patients without obesity – with normal body weight (NBW)). The control group included 20 apparently healthy individuals with NBW. The patients underwent detailed standard clinical, laboratory and instrumental examination. Determination of the quantitative composition of GM was carried out by the method of polymerase chain reaction with hybridization-fluorescence detection of results in real time using the test system “COLONOFLOR-16 (biocenosis)” (“ALFA-LAB”). In this work, a statistical analysis of the obtained data was carried out using standard methods and Microsoft Excel 17.0. Results. A significant change in the composition of GM were found in patients with AH, which proceeds against the background of AO, in comparison with apparently healthy individuals and with patients with AH without obesity (with NBW). In the group of AH patients with the presence of AO, significant decrease in the number of Lactobacillus spp., Bifidobacterium spp., Faecalibacterium prausnitzii and Аkkermansia muciniphila was found in comparison with apparently healthy individuals. The number of Faecalibacterium prausnitzii and Аkkermansia muciniphila in these patients was also significantly lower than in hypertensive patients with NBW. At the same time, the ratio of Bacteroides fragilis/Faecalibacterium prausnitzii was significantly higher than in the control group and the group of hypertensive patients without obesity – with NBW. Conclusions. The results of the study indicate a possible role for the deficiency of such representatives of GM as Lactobacillus spp., Bifidobacterium spp., Faecalibacterium prausnitzii and Аkkermansia muciniphila and an increase in the ratio of Bacteroides fragilis/Faecalibacterium prausnitzii in the pathogenesis of AH, which occurs against the background of AO.

High frequency of enterotoxigenic Bacteroides fragilis and Enterococcus faecalis in the paraffin-embedded tissues of Iranian colorectal cancer patients

Background The association between specific bacteria and colorectal cancer (CRC) has been proposed. Only a few studies have, however, investigated this relationship directly in colorectal tissue with conflicting results. So, we aimed to quantitate Streptococcus gallolyticus, Fusobacterium spp, Enterococcus faecalis and enterotoxigenic Bacteroides fragilis (ETBF) in formalin-fixed and paraffin-embedded (FFPE) colorectal tissue samples of Iranian CRC patients and healthy controls. Methods A total of 80 FFPE colorectal tissue samples of CRC patients (n = 40) and healthy controls (n = 40) were investigated for the presence and copy number of above bacterial species using quantitative PCR. Relative quantification was determined using ΔΔCT method and expressed as relative fold difference compared to reference gene. Results Relative abundance and copy number of E. faecalis and ETBF were significantly higher in CRC samples compared to control group. E. faecalis was more prevalent than ETBF in tumor samples. Frequency of ETBF and E. faecalis in late stages (III/IV) of cancer was significantly higher than early stages (I/II). We did not detect a significant difference in abundance of S. gallolyticus and Fusobacterium spp between two groups. Conclusion Our study revealed the higher concentration of E. faecalis and ETBF in FFPE samples of CRC patients than controls. However, additional investigations on fecal and fresh colorectal cancer tissue samples are required to substantiate this correlation.