Enterohepatic Helicobacter in ulcerative colitis:Potential pathogenic entities?

Background: Changes in bacterial populations termed "dysbiosis" are thought central to ulcerative colitis (UC) pathogenesis. In particular, the possibility that novel Helicobacter organisms play a role in human UC has been debated but not comprehensively investigated. The aim of this study was to develop a molecular approach to investigate the presence of Helicobacter organisms in adults with and without UC.Methodology/Principal Findings: A dual molecular approach to detect Helicobacter was developed. Oligonucleotide probes against the genus Helicobacter were designed and optimised alongside a validation of published H. pylori probes. A comprehensive evaluation of Helicobacter genus and H. pylori PCR primers was also undertaken. The combined approach was then assessed in a range of gastrointestinal samples prior to assessment of a UC cohort. Archival colonic samples were available from 106 individuals for FISH analysis (57 with UC and 49 non-IBD controls). A further 118 individuals were collected prospectively for dual FISH and PCR analysis (86 UC and 32 non-IBD controls). An additional 27 non-IBD controls were available for PCR analysis. All Helicobacter PCR-positive samples were sequenced. The association between Helicobacter and each study group was statistically analysed using the Pearson Chi Squared 2 tailed test. Helicobacter genus PCR positivity was significantly higher in UC than controls (32 of 77 versus 11 of 59, p = 0.004). Sequence analysis indicated enterohepatic Helicobacter species prevalence was significantly higher in the UC group compared to the control group (30 of 77 versus 2 of 59, p&lt;0.0001). PCR and FISH results were concordant in 74 (67.9%) of subjects. The majority of discordant results were attributable to a higher positivity rate with FISH than PCR.Conclusions/Significance: Helicobacter organisms warrant consideration as potential pathogenic entities in UC. Isolation of these organisms from colonic tissue is needed to enable interrogation of pathogenicity against established criteria.</p

The inflammatory microenvironment in colorectal neoplasia

Peer reviewedPublisher PD

Sporadic colorectal cancer - role of the commensual microbiota

There are vast numbers of bacteria present within the human colon and many studies have implicated these in CRC development.  Despite this evidence, microbial diversity present at the mucosal surface has not been well characterised, with many investigations using culturing methods or extrapolating from analysis on faecal material.  In this thesis, molecular analysis of colonic mucosal microbial diversity (caecum to rectum) in 10 healthy individuals revealed that each individual harboured their own microbial cohort that remained constant throughout the colon.  Detailed 16S rDNA cloning and sequence analysis of caecal and rectal tissue from 1 individual reflected DGGE findings and showed the majority of sequences affiliated with the low G + C bacterial phylum, namely Clostridium  cluster IV, XIVa and also the Bacteroides subphylum.  DGGE and sequence analysis of a faecal sample from the same individual showed major differences in microbial diversity compared to tissue samples.  DGGE analysis of paired neoplastic and adjacent normal mucosa samples revealed differences in microbial populations between the 2 tissues in a significant number of paired polyp samples.  A number of cancer/normal tissue paired samples also displayed altered microbial diversity.  Lectin immunohistochemistry was performed on selected healthy individuals and a number of paired neoplastic/normal colonic samples in order to determine host carbohydrate expression.  Analysis of healthy tissue revealed individual glycosylation patterns, whilst neoplastic samples often showed altered glycosylation.  Changes in host glycosylation did not appear to correlate with microbial diversity.  RT-PCR was used to investigate gene expression of several fucosyltranferases in healthy individuals and selected neoplastic tissues.  Downregulation in FUT3 expression was found in cancer tissue, correlating with loss of fucose-specific lectin staining in cancer tissue samples.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Increase in NF-κB Binding Affinity of the Variant C Allele of the Toll-Like Receptor 9 −1237T/C Polymorphism Is Associated with Helicobacter pylori-Induced Gastric Disease▿

Colonization of the gastric mucosa by Helicobacter pylori can lead to serious clinical outcomes, including gastric cancer. Toll-like receptors (TLRs) play an important role in the host response to H. pylori through the recognition of pathogen-associated molecular patterns. TLR9, in particular, is partly responsible for initiating bacterial induced immunity by binding unmethylated CpG-DNA, which is abundant in bacteria. A well-documented single nucleotide polymorphism (SNP) within the TLR9 promoter (TLR9 −1237T/C), is associated with a variety of inflammatory disorders, including allergic asthma, inflammatory bowel disease, and atopy. Analysis of the TLR9 promoter gene sequence has shown that carriage of the variant “C” allele at position −1237 creates a potential NF-κB binding site that would theoretically increase the transcriptional activity of the gene. In this study, we report that the TLR9 −1237 C allele was significantly associated with the development of H. pylori-induced premalignant gastric changes. Functional analysis of the SNP, supporting the data generated from the genetic association study, showed that carriage of the C allele increased TLR9 transcriptional activity driven mainly by activation of NF-κB. Collectively, these findings confirm that the TLR9 −1237T/C polymorphism is a risk factor for the development of H. pylori-induced premalignant gastric changes and provide a plausible mechanistic explanation