Campylobacter concisus: an evaluation of certain phenotypic and genotypic characteristics

Global epidemiology of campylobacteriosis and the impact of COVID-19

Campylobacteriosis is a gastroenteritis caused by pathogenic Campylobacter species and an important topic in public health. Here we review the global epidemiology of campylobacteriosis in the last eight years between 2014-2021, providing comprehensive and updated information on the reported incidence and outbreaks of Campylobacter infections. The government public health website of each of the 195 countries and publications from 2014 to September 2022 in public databases were searched. The reported incidence of campylobacteriosis in pre-COVID-19 years was compared to that during the COVID-19 pandemic in countries where data were available. Czech Republic had the highest reported incidence of campylobacteriosis worldwide (215 per 100,000 in 2019), followed by Australia (146.8 per 100,000 in 2016) and New Zealand (126.1 per 100,000 in 2019). Campylobacter was one of the most common human enteric pathogens in both developed and developing countries. About 90% of cases of campylobacteriosis were caused by Campylobacter jejuni, whereas less than 10% of cases were caused by Campylobacter coli. Other Campylobacter species were also isolated. The reported incidence and case numbers of campylobacteriosis in developed nations have remained steadily high prior to the COVID-19 pandemic, whilst some countries reported an increasing trend such as France and Japan. While outbreaks were more frequently reported in some countries, Campylobacter infections were mainly sporadic cases in most of the developed countries. Campylobacter infection was more common in summer in some but not all countries. Campylobacter infection was more common in males than females. The COVID-19 pandemic has reduced the reported incidence of campylobacteriosis in most countries where 2020 epidemiology data were available. In conclusion, Campylobacter infection remains a global health concern. Increased research and improved strategies are needed for prevention and reduction of Campylobacter infection.

Genetic characterisation of Campylobacter concisus: Strategies for improved genomospecies discrimination

Although at least two genetically distinct groups, or genomospecies, have been well documented for Campylobacter concisus, no phenotype has yet been identified for their differentiation and thus formal description as separate species. C. concisus has been isolated from a variety of sites in the human body, including saliva and stool samples from both healthy and diarrhoeic individuals. We evaluated the ability of a range of whole genome-based tools to distinguish between the two C. concisus genomospecies (GS) using a collection of 190 C. concisus genomes. Nine genomes from related Campylobacter species were included in some analyses to provide context. Analyses incorporating sequence analysis of multiple ribosomal genes generated similar levels of C. concisus GS discrimination as genome-wide comparisons. The C. concisus genomes formed two groups; GS1 represented by ATCC 33237^T and GS2 by CCUG 19995. The two C. concisus GS were separated from the nine genomes of related species. GS1 and GS2 also differed in G+C content with medians of 37.56% and 39.51%, respectively. The groups are consistent with previously established GS and are supported by DNA reassociation results. Average Nucleotide Identity using MUMmer (ANIm) and Genome BLAST Distance Phylogeny generated in silico DNA-DNA hybridisation (isDDH) (against ATCC 33237^T and CCUG 19995), plus G+C content provides cluster-independent GS discrimination suitable for routine use. Pan-genomic analysis identified genes specific to GS1 and GS2. WGS data and genomic species identification methods support the existence of two GS within C. concisus. These data provide genome-level metrics for strain identification to genomospecies level.

Tongue coating microbiome as a potential biomarker for gastritis including precancerous cascade

The development of gastritis is associated with an increased risk of gastric cancer. Current invasive gastritis diagnostic methods are not suitable for monitoring progress. In this work based on 78 gastritis patients and 50 healthy individuals, we observed that the variation of tongue-coating microbiota was associated with the occurrence and development of gastritis. Twenty-one microbial species were identified for differentiating tongue-coating microbiomes of gastritis and healthy individuals. Pathways such as microbial metabolism in diverse environments, biosynthesis of antibiotics and bacterial chemotaxis were up-regulated in gastritis patients. The abundance of Campylobacter concisus was found associated with the gastric precancerous cascade. Furthermore, Campylobacter concisus could be detected in tongue coating and gastric fluid in a validation cohort containing 38 gastritis patients. These observations provided biological evidence of tongue diagnosis in traditional Chinese medicine, and indicated that tongue-coating microbiome could be a potential non-invasive biomarker, which might be suitable for long-term monitoring of gastritis.

Campylobacter Concisus and Its Effect on the Expression of CDX1 and COX2

Background: Barrett’s oesophagus (BO) is a pre-malignant condition in which normal squamous epithelium of the lower oesophagus and gastresophageal junction is replaced by columnar cells and progress to oesophageal adenocarcinoma. The increase burden of oesophagus cancer morbidity and mortality worldwide make study of factors involved in the pathogenesis of BO essential. However, most of studies that examine the environmental risk factors associated with increased incidence and prevalence of BO have largely ignored the potential role of bacteria in disease aetiology. Aims: This study examined the role of Campylobacter concisus isolated from Barrett’s and adenocarcinoma patient samples as one of possible environmental factors in the progression of Barrett’s oesophagus to oesophagus adenocarcinoma. Methods: We focused on the effect of C. concisus on the expression caudal type homeobox 1 gene (CDX1) and cyclooxygenase-2 (COX-2) in three BO cell lines using quantitative real-time PCR. In addition, the attachment and invasion characteristics of C. concisus were also tested. Results: Results showed that C. concisus had a strong attachment to the cell lines and induce the expression of CDX1 in Barrett’s cell lines in a time-dependent manner. Conclusion: Findings indicate that C. concisus could be as a new challenge in the progression of BO to adenocarcinoma.

The Clinical Importance of Campylobacter concisus and Other Human Hosted Campylobacter Species

Historically, Campylobacteriosis has been considered to be zoonotic; the Campylobacter species that cause human acute intestinal disease such as Campylobacter jejuni and Campylobacter coli originate from animals. Over the past decade, studies on human hosted Campylobacter species strongly suggest that Campylobacter concisus plays a role in the development of inflammatory bowel disease (IBD). C. concisus primarily colonizes the human oral cavity and some strains can be translocated to the intestinal tract. Genome analysis of C. concisus strains isolated from saliva samples has identified a bacterial marker that is associated with active Crohn's disease (one major form of IBD). In addition to C. concisus, humans are also colonized by a number of other Campylobacter species, most of which are in the oral cavity. Here we review the most recent advancements on C. concisus and other human hosted Campylobacter species including their clinical relevance, transmission, virulence factors, disease associated genes, interactions with the human immune system and pathogenic mechanisms.

The Growth and Protein Expression of Inflammatory Bowel Disease-Associated Campylobacter concisus Is Affected by the Derivatives of the Food Additive Fumaric Acid

Inflammatory bowel diseases (IBD) are chronic inflammatory conditions of the gastrointestinal tract with multifactorial etiology. Both dietary factors and the microbe Campylobacter concisus have been found to be associated with the condition. The current study examined the effects of sodium fumarate, a neutralized product of the food additives fumaric acid and monosodium fumarate when in the intestinal environment, on the growth of C. concisus to determine the effects of these food additives on IBD-associated bacterial species. Through culture methods and quantification, it was found that neutralized fumaric acid, neutralized monosodium fumarate, and sodium fumarate increased the growth of C. concisus, with the greatest increase in growth at a concentration of 0.4%. Further examination of 50 C. concisus strains on media with added sodium fumarate showed that greatest growth was also achieved at a concentration of 0.4%. At a concentration of 2% sodium fumarate, all strains examined displayed less growth in comparison with those cultured on media without sodium fumarate. Using mass spectrometry, multiple C. concisus proteins showed significant differential expression when cultured on media with and without 0.4% sodium fumarate. The findings presented suggest that patients with IBD should consider avoiding excessive consumption of foods with fumaric acid or its sodium salts, and that the addition of 0.4% sodium fumarate alone to media may assist in the isolation of C. concisus from clinical samples.

Genomic analysis of oral Campylobacter concisus strains identified a potential bacterial molecular marker associated with active Crohn's disease

Campylobacter concisus is an oral bacterium that is associated with inflammatory bowel disease (IBD) including Crohn's disease (CD) and ulcerative colitis (UC). C. concisus consists of two genomospecies (GS) and diverse strains. This study aimed to identify molecular markers to differentiate commensal and IBD-associated C. concisus strains. The genomes of 63 oral C. concisus strains isolated from patients with IBD and healthy controls were examined, of which 38 genomes were sequenced in this study. We identified a novel secreted enterotoxin B homologue, Csep1. The csep1 gene was found in 56% of GS2 C. concisus strains, presented in the plasmid pICON or the chromosome. A six-nucleotide insertion at the position 654-659 bp in csep1 (csep1-6bpi) was found. The presence of csep1-6bpi in oral C. concisus strains isolated from patients with active CD (47%, 7/15) was significantly higher than that in strains from healthy controls (0/29, P = 0.0002), and the prevalence of csep1-6bpi positive C. concisus strains was significantly higher in patients with active CD (67%, 4/6) as compared to healthy controls (0/23, P = 0.0006). Proteomics analysis detected the Csep1 protein. A csep1 gene hot spot in the chromosome of different C. concisus strains was found. The pICON plasmid was only found in GS2 strains isolated from the two relapsed CD patients with small bowel complications. This study reports a C. concisus molecular marker (csep1-6bpi) that is associated with active CD.

Molecular epidemiology and comparative genomics of Campylobacter concisus strains from saliva, faeces and gut mucosal biopsies in inflammatory bowel disease

Campylobacter concisus is an emerging pathogen associated with inflammatory bowel disease (IBD), yet little is known about the genetic diversity of C. concisus in relation to host niches and disease. We isolated 104 C. concisus isolates from saliva, mucosal biopsies and faecal samples from 41 individuals (26 IBD, 3 Gastroenteritis (GE), 12 Healthy controls (HC)). Whole genomes were sequenced and the dataset pan-genome examined, and genomic information was used for typing using multi-locus-sequence typing (MLST). C. concisus isolates clustered into two main groups/genomospecies (GS) with 71 distinct sequence types (STs) represented. Sampling site (p < 0.001), rather than disease phenotype (p = 1.00) was associated with particular GS. We identified 97 candidate genes associated with increase or decrease in prevalence during the anatomical descent from the oral cavity to mucosal biopsies to faeces. Genes related to cell wall/membrane biogenesis were more common in oral isolates, whereas genes involved in cell transport, metabolism and secretory pathways were more prevalent in enteric isolates. Furthermore, there was no correlation between individual genetic diversity and clinical phenotype. This study confirms the genetic heterogeneity of C. concisus and provides evidence that genomic variation is related to the source of isolation, but not clinical phenotype.

Campylobacter concisus Genomospecies 2 Is Better Adapted to the Human Gastrointestinal Tract as Compared with Campylobacter concisus Genomospecies 1

Campylobacter concisus was previously shown to be associated with inflammatory bowel disease including Crohn's disease (CD) and ulcerative colitis (UC). C. concisus has two genomospecies (GS). This study systematically examined the colonization of GS1 and GS2 C. concisus in the human gastrointestinal tract. GS1 and GS2 specific polymorphisms in 23S rRNA gene were identified by comparison of the 23S rRNA genes of 49 C. concisus strains. Two newly designed PCR methods, based on the polymorphisms of 23S rRNA gene, were developed and validated. These PCR methods were used to detect and quantify GS1 and GS2 C. concisus in 56 oral and enteric samples collected from the gastrointestinal tract of patients with IBD and healthy controls. Meta-analysis of the composition of the isolated GS1 and GS2 C. concisus strains in previous studies was also conducted. The quantitative PCR methods revealed that there was more GS2 than GS1 C. concisus in samples collected from the upper and lower gastrointestinal tract of both patients with IBD and healthy controls, showing that GS2 C. concisus is better adapted to the human gastrointestinal tract. Analysis of GS1 and GS2 composition of isolated C. concisus strains in previous studies showed similar findings except that in healthy individuals a significantly lower GS2 than GS1 C. concisus strains were isolated from fecal samples, suggesting a potential difference in the C. concisus strains or the enteric environment between patients with gastrointestinal diseases and healthy controls. This study provides novel information regarding the adaptation of different genomospecies of C. concisus in the human gastrointestinal tract.

Genome analysis of Campylobacter concisus strains from patients with inflammatory bowel disease and gastroenteritis provides new insights into pathogenicity

Campylobacter concisus is an oral bacterium that is associated with inflammatory bowel disease. C. concisus has two major genomospecies, which appear to have different enteric pathogenic potential. Currently, no studies have compared the genomes of C. concisus strains from different genomospecies. In this study, a comparative genome analysis of 36 C. concisus strains was conducted including 27 C. concisus strains sequenced in this study and nine publically available C. concisus genomes. The C. concisus core-genome was defined and genomospecies-specific genes were identified. The C. concisus core-genome, housekeeping genes and 23S rRNA gene consistently divided the 36 strains into two genomospecies. Two novel genomic islands, CON_PiiA and CON_PiiB, were identified. CON_PiiA and CON_PiiB islands contained proteins homologous to the type IV secretion system, LepB-like and CagA-like effector proteins. CON_PiiA islands were found in 37.5% of enteric C. concisus strains (3/8) isolated from patients with enteric diseases and none of the oral strains (0/27), which was statistically significant. This study reports the findings of C. concisus genomospecies-specific genes, novel genomic islands that contain type IV secretion system and putative effector proteins, and other new genomic features. These data provide novel insights into understanding of the pathogenicity of this emerging opportunistic pathogen.

Multilocus sequence typing of Campylobacter concisus from Danish diarrheic patients

The emerging enteric pathogen Campylobacter concisus is associated with prolonged diarrhea and inflammatory bowel disease. Previous studies have shown that C. concisus strains are very genetically diverse. Nevertheless, C. concisus strains have been divided into two genomospecies, where GS1 strains have been isolated predominantly from healthy individuals, while the GS2 cluster consists of isolates primarily from diarrheic individuals. The aim of the present study was to determine the genetic diversity of C. concisus isolates from Danish diarrheic patients. Multilocus sequence typing using the loci aspA, atpA, glnA, gltA, glyA, ilvD and pgm, as well as genomospecies based on specific differences in the 23S rRNA, was used to characterize 67 isolates (63 fecal and 4 oral), from 49 patients with different clinical presentations (29 with diarrhea, eight with bloody diarrhea, seven with collagenous colitis and five with Crohn’s disease). MLST revealed a high diversity of C. concisus with 53 sequence types (STs), of which 52 were identified as ‘new’ STs. Allele sequences showed more than 90 % similarity between isolates, with only four outliers. Dendrogram profiles of each allele showed a division into two groups, which more or less correlated with genomospecies A and genomospecies B. However, in contrary to previous results, this subgrouping had no association to the clinical severity of disease.

The Effect of Campylobacter concisus on Expression of IL-18, TNF-α and p53 in Barrett's Cell Lines

BACKGROUND

Barrett's oesophagus is a pre-malignant condition at gastroesophageal junction in which normal squamous epithelium is replaced by columnar shape epithelium, which predisposes oesophageal adenocarcinoma. It is known that Barrett's oesophagus evolves as a consequence of chronic gastro-oesophageal reflux disease. Although progression of Barrett's oesophagus to adenocarcinoma is still unclear, increasing incidence of oesophageal cancer and mortality worldwide make its study necessary. Several investigations have been made on the aetiology of oesophageal cancer. Most of them assessed genetical or environmental factors. However, potential role of bacteria in the development of oesophageal adenocarcinoma as a new environmental factor has not been addressed. Previous study on Barrett's disease detected presence of Campylobacter concisus as a new emerging pathogen on Barrett's and oesophageal cancer samples compared with healthy individuals. This indicates that this organism might involve in the progression of Barrett's to oesophageal adenocarcinoma.

OBJECTIVES

This study aimed to determine the effects of C. concisus on expression of three biomarkers including interleukin-18 (IL-18), tumour necrosis factor-α (TNF-α) and tumour suppressor gene (p53) in three Barrett's cell lines.

MATERIALS AND METHODS

Quantitative real-time PCR assays were developed to measure expression of pro-inflammatory mediators (IL-18 and TNF-α) and gene expression of p53 in Barrett's cell lines in co-culture with C. concisus.

RESULTS

The mentioned organism was able to modulate considerably expression of p53, TNF-α and IL-18 in a time-dependent manner.

CONCLUSIONS

The results showed that microorganism influences expression of carcinogenesis biomarker and cytokines in cell line models and possibility promotes oesophageal adenocarcinoma.

Global Epidemiology of Campylobacter Infection

Campylobacter jejuni infection is one of the most widespread infectious diseases of the last century. The incidence and prevalence of campylobacteriosis have increased in both developed and developing countries over the last 10 years. The dramatic increase in North America, Europe, and Australia is alarming, and data from parts of Africa, Asia, and the Middle East indicate that campylobacteriosis is endemic in these areas, especially in children. In addition to C. jejuni, there is increasing recognition of the clinical importance of emerging Campylobacter species, including Campylobacter concisus and Campylobacter ureolyticus. Poultry is a major reservoir and source of transmission of campylobacteriosis to humans. Other risk factors include consumption of animal products and water, contact with animals, and international travel. Strategic implementation of multifaceted biocontrol measures to reduce the transmission of this group of pathogens is paramount for public health. Overall, campylobacteriosis is still one of the most important infectious diseases that is likely to challenge global health in the years to come. This review provides a comprehensive overview of the global epidemiology, transmission, and clinical relevance of Campylobacter infection.

Role of emerging Campylobacter species in inflammatory bowel diseases

The gut microbiota is a central player in the etiology of inflammatory bowel diseases. As such, there is intense scientific interest in elucidating the specific group/s of bacteria responsible for driving barrier damage and perpetuating the chronic inflammation that results in disease. Because of their ability to colonize close to the surface of the host intestinal epithelium, mucosa-associated bacteria are considered key players in the initiation and development of both Crohn's disease and ulcerative colitis. The leading bacterial candidates include adherent and invasive Escherichia coli, Helicobacter, Fusobacteria, Mycobacteria, and Campylobacter species. Of these, a member of the Campylobacter genus, Campylobacter concisus, has recently emerged as a putative player in the pathogenesis of inflammatory bowel diseases. Current research indicates that this bacterium possesses extraordinarily diverse pathogenic capacities as well as unique genetic and functional signatures that are defined by their ability to adhere to and invade host cells, secrete toxins, and the presence of a virulence-associated restriction-modification system. These characteristics enable the potential classification of C. concisus into distinct pathotypes, which we have named adherent and invasive C. concisus and adherent and toxinogenic C. concisus. In this review, we evaluate evidence for the role of emerging Campylobacter species in the pathogenesis of inflammatory bowel diseases.

Role of the gut microbiota in inflammatory bowel disease pathogenesis: What have we learnt in the past 10 years?

Our understanding of the microbial involvement in inflammatory bowel disease (IBD) pathogenesis has increased exponentially over the past decade. The development of newer molecular tools for the global assessment of the gut microbiome and the identification of nucleotide-binding oligomerization domain-containing protein 2 in 2001 and other susceptibility genes for Crohn’s disease in particular has led to better understanding of the aetiopathogenesis of IBD. The microbial studies have elaborated the normal composition of the gut microbiome and its perturbations in the setting of IBD. This altered microbiome or “dysbiosis” is a key player in the protracted course of inflammation in IBD. Numerous genome-wide association studies have identified further genes involved in gastrointestinal innate immunity (including polymorphisms in genes involved in autophagy: ATG16L1 and IGRM), which have helped elucidate the relationship of the local innate immunity with the adjacent luminal bacteria. These developments have also spurred the search for specific pathogens which may have a role in the metamorphosis of the gut microbiome from a symbiotic entity to a putative pathogenic one. Here we review advances in our understanding of microbial involvement in IBD pathogenesis over the past 10 years and offer insight into how this will shape our therapeutic management of the disease in the coming years.

Clinical manifestations of Campylobacter concisus infection in children

BACKGROUND

There is only sparse information about the clinical impact of Campylobacter concisus infections in children.

METHODS

A study was performed during a 2-year period to determine the clinical manifestations in C. concisus-positive children with gastroenteritis. A case patient was defined as a child or teenager (<18 years) with a C. concisus-positive stool sample during the study period. Clinical data were obtained with use of a questionnaire study supplemented with the patients' medical records. The clinical manifestations in these patients were compared with those of patients with Campylobacter jejuni/coli infection.

RESULTS

Two thousand three hundred seventy-two diarrheic stool samples from 1867 children were cultured for pathogenic enteric bacteria during the study period, and 85 and 109 children with C. concisus and C. jejuni/coli, respectively, were identified. Comparison of the acute clinical manifestations in 44 C. concisus patients with those in 64 C. jejuni/coli patients showed a significantly lower prevalence of fever, chills and blood in stools in the former. However, half of C. concisus patients compared with one-fourth of C. jejuni/coli patients had prolonged diarrhea for more than 2 weeks and two-thirds of all children with C. concisus reported loose stools after 6-month follow-up.

CONCLUSIONS

C. concisus infection in children seems to have a milder course of acute gastroenteritis compared with C. jejuni/coli infection but is associated with more prolonged diarrhea. Children with C. concisus have the same degree of late gastrointestinal complaints as children diagnosed with C. jejuni/coli infection.

Investigation of the enteric pathogenic potential of oral Campylobacter concisus strains isolated from patients with inflammatory bowel disease

BACKGROUND

Campylobacter concisus, a bacterium colonizing the human oral cavity, has been shown to be associated with inflammatory bowel disease (IBD). This study investigated if patients with IBD are colonized with specific oral C. concisus strains that have potential to cause enteric diseases.

METHODOLOGY

Seventy oral and enteric C. concisus isolates obtained from eight patients with IBD and six controls were examined for housekeeping genes by multilocus sequence typing (MLST), Caco2 cell invasion by gentamicin-protection-assay, protein analysis by mass spectrometry and SDS-PAGE, and morphology by scanning electron microscopy. The whole genome sequenced C. concisus strain 13826 which was isolated from an individual with bloody diarrhea was included in MLST analysis.

PRINCIPAL FINDINGS

MLST analysis showed that 87.5% of individuals whose C. concisus belonged to Cluster I had inflammatory enteric diseases (six IBD and one with bloody diarrhea), which was significantly higher than that in the remaining individuals (28.6%) (P<0.05). Enteric invasive C. concisus (EICC) oral strain was detected in 50% of patients with IBD and none of the controls. All EICC strains were in Cluster 1. The C. concisus strain colonizing intestinal tissues of patient No. 1 was closely related to the oral C. concisus strain from patient No. 6 and had gene recombination with the patient's own oral C. concisus. The oral and intestinal C. concisus strains of patient No. 3 were the same strain. Some individuals were colonized with multiple oral C. concisus strains that have undergone natural recombination.

CONCLUSIONS

This study provides the first evidence that patients with IBD are colonized with specific oral C. concisus strains, with some being EICC strains. C. concisus colonizing intestinal tissues of patients with IBD at least in some instances results from an endogenous colonization of the patient's oral C. concisus and that C. concisus strains undergo natural recombination.

Multilocus sequence typing methods for the emerging Campylobacter Species C. hyointestinalis, C. lanienae, C. sputorum, C. concisus, and C. curvus

Multilocus sequence typing (MLST) systems have been reported previously for multiple food- and food animal-associated Campylobacter species (e.g., C. jejuni, C. coli, C. lari, and C. fetus) to both differentiate strains and identify clonal lineages. These MLST methods focused primarily on campylobacters of human clinical (e.g., C. jejuni) or veterinary (e.g., C. fetus) relevance. However, other, emerging, Campylobacter species have been isolated increasingly from environmental, food animal, or human clinical samples. We describe herein four MLST methods for five emerging Campylobacter species: C. hyointestinalis, C. lanienae, C. sputorum, C. concisus, and C. curvus. The concisus/curvus method uses the loci aspA, atpA, glnA, gltA, glyA, ilvD, and pgm, whereas the other methods use the seven loci defined for C. jejuni (i.e., aspA, atpA, glnA, gltA, glyA, pgm, and tkt). Multiple food animal and human clinical C. hyointestinalis (n = 48), C. lanienae (n = 34), and C. sputorum (n = 24) isolates were typed, along with 86 human clinical C. concisus and C. curvus isolates. A large number of sequence types were identified using all four MLST methods. Additionally, these methods speciated unequivocally isolates that had been typed ambiguously using other molecular-based speciation methods, such as 16S rDNA sequencing. Finally, the design of degenerate primer pairs for some methods permitted the typing of related species; for example, the C. hyointestinalis primer pairs could be used to type C. fetus strains. Therefore, these novel Campylobacter MLST methods will prove useful in differentiating strains of multiple, emerging Campylobacter species.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

IBD-what role do Proteobacteria play?

The gastrointestinal microbiota has come to the fore in the search for the causes of IBD. This shift has largely been driven by the finding of genetic polymorphisms involved in gastrointestinal innate immunity (particularly polymorphisms in NOD2 and genes involved in autophagy) and alterations in the composition of the microbiota that might result in inflammation (so-called dysbiosis). Microbial diversity studies have continually demonstrated an expansion of the Proteobacteria phylum in patients with IBD. Individual Proteobacteria, in particular (adherent-invasive) Escherichia coli, Campylobacter concisus and enterohepatic Helicobacter, have all been associated with the pathogenesis of IBD. In this Review, we comprehensively describe the various associations of Proteobacteria and IBD. We also examine the importance of pattern recognition in the extracellular innate immune response of the host with particular reference to Proteobacteria, and postulate that Proteobacteria with adherent and invasive properties might exploit host defenses, drive proinflammatory change, alter the intestinal microbiota in favor of dysbiosis and ultimately lead to the development of IBD.

Campylobacter concisus - A new player in intestinal disease

Over the last decade Campylobacter concisus, a highly fastidious member of the Campylobacter genus has been described as an emergent pathogen of the human intestinal tract. Historically, C. concisus was associated with the human oral cavity and has been linked with periodontal lesions, including gingivitis and periodontitis, although currently its role as an oral pathogen remains contentious. Evidence to support the role of C. concisus in acute intestinal disease has come from studies that have detected or isolated C. concisus as sole pathogen in fecal samples from diarrheic patients. C. concisus has also been associated with chronic intestinal disease, its prevalence being significantly higher in children with newly diagnosed Crohn’s disease (CD) and adults with ulcerative colitis than in controls. Further C. concisus has been isolated from biopsy specimens of patients with CD. While such studies support the role of C. concisus as an intestinal pathogen, its isolation from healthy individuals, and failure of some studies to show a significant difference in C. concisus prevalence in subjects with diarrhea and healthy controls has raised contention as to its role in intestinal disease. Such findings could argue against the role of C. concisus in intestinal disease, however, the fact that C. concisus strains are genetically diverse raises the possibility that differences exist in their pathogenic potential. Evidence to support this view comes from studies showing strain specific differences in the ability of C. concisus to attach to and invade cells and produce virulence factors, including toxins and hemolytic phospholipase A. Further, sequencing of the genome of a C. concisus strain isolated from a child with CD (UNSWCD) and comparison of this with the only other fully sequenced strain (BAA-1457) would suggest that major differences exist in the genetic make-up of this species which could explain different outcomes of C. concisus infection.

Immunoreactive proteins of Campylobacter concisus, an emergent intestinal pathogen

Campylobacter concisus is an emerging pathogen of the human gastrointestinal tract. Recently, a significantly higher prevalence of C. concisus DNA and higher levels of antibodies specific to C. concisus was detected in children with Crohn's disease when compared with controls. The aim of this study was to identify C. concisus immunoreactive antigens. Proteins from C. concisus were separated using two-dimensional gel electrophoresis, and sera from 10 C. concisus-positive children with Crohn's disease were employed for immunoprobing. The patients' sera reacted with 69 spots, which corresponded to 31 proteins identified by mass spectrometry. The proteins were functionally classified as involved in chemotaxis, signal transduction, flagellar motility, surface binding and membrane protein assembly. Although the individual patients' sera reacted to different sets of proteins, common antigens that were recognized by all patients were flagellin B, ATP synthase F1 alpha subunit, and outer membrane protein 18. Cross-reactivity between proteins of the Campylobacter genus was tested using patients' sera absorbed with Campylobacter showae, Campylobacter jejuni and Campylobacter ureolyticus. Most of the C. concisus immunoreactive proteins identified in this study showed cross-reactivity with other species except for three antigens. In conclusion, this study has identified C. concisus proteins that are immunoreactive within patients with Crohn's disease.

The clinical importance of emerging Campylobacter species

A growing number of Campylobacter species other than C. jejuni and C. coli have been recognized as emerging human and animal pathogens. Although C. jejuni continues to be the leading cause of bacterial gastroenteritis in humans worldwide, advances in molecular biology and development of innovative culture methodologies have led to the detection and isolation of a range of under-recognized and nutritionally fastidious Campylobacter spp., including C. concisus, C. upsaliensis and C. ureolyticus. These emerging Campylobacter spp. have been associated with a range of gastrointestinal diseases, particularly gastroenteritis, IBD and periodontitis. In some instances, infection of the gastrointestinal tract by these bacteria can progress to life-threatening extragastrointestinal diseases. Studies have shown that several emerging Campylobacter spp. have the ability to attach to and invade human intestinal epithelial cells and macrophages, damage intestinal barrier integrity, secrete toxins and strategically evade host immune responses. Members of the Campylobacter genus naturally colonize a wide range of hosts (including pets, farm animals and wild animals) and are frequently found in contaminated food products, which indicates that these bacteria are at risk of zoonotic transmission to humans. This Review presents the latest information on the role and clinical importance of emerging Campylobacter spp. in gastrointestinal health and disease.

Comparative analyses of Campylobacter concisus strains reveal the genome of the reference strain BAA-1457 is not representative of the species

Background

Several studies have shown that significant genotypic heterogeneity exists among Campylobacter concisus strains. Recently, the genome of C. concisus UNSWCD, isolated from a patient with Crohn's disease, was sequenced.

Results

In this study, comparative analyses were performed between strain UNSWCD and BAA-1457, isolated from a patient with acute gastroenteritis. Searches between C. concisus UNSWCD and BAA-1457 showed that 76% of genes were homologues, whereas those between C. jejuni strains showed 90-91% to be homologues, indicating substantial variation exists within these two C. concisus genomes. More specific bidirectional homology searches identified 1593 genes that are shared between these strains, and 115 and 281 genes unique to UNSWCD and BAA-1457, respectively. Significantly, differences in the type of flagellin glycosylation pathways between the two strains were identified and confirmed by PCR. The protein profiles of UNSWCD, BAA-1457 and a further six strains of C. concisus were compared and analyzed bioinformatically, and this differentiated the strains into four clades. BAA-1457 was found to be highly divergent (average similarity: 56.8%) from the other seven strains (mean average similarity ± standard deviation: 64.7 ± 1.7%). Furthermore, searches for homologues of the 1593 proteins found to be common between UNSWCD and BAA-1457 were conducted against all available bacterial genomes, and 18 proteins were found to be unique to C. concisus, of which 6 were predicted to be secreted, and may represent good markers for detection of this species.

Conclusions

This study has elucidated several features that may be responsible for the heterogeneity that exists among C. concisus strains, and has determined that the strain BAA-1457 is genetically atypical to other C. concisus strains and is not a good candidate reference strain.

Prevalence of Campylobacter species in adult Crohn's disease and the preferential colonization sites of Campylobacter species in the human intestine

INTRODUCTION

Crohn's disease (CD) and ulcerative colitis (UC) are the two major forms of inflammatory bowel disease (IBD). A high prevalence of Campylobacter concisus was previously detected in paediatric CD and adult UC. Currently, the prevalence of C. concisus in adult CD and the preferential colonization sites of Campylobacter species in the human intestine are unknown. In this study, we examined the prevalence of Campylobacter species in biopsies collected from multiple anatomic sites of adult patients with IBD and controls.

METHODS

Three hundred and one biopsies collected from ileum, caecum, descending colon and rectum of 28 patients IBD (15 CD and 13 UC) and 33 controls were studied. Biopsies were used for DNA extraction and detection of Campylobacter species by PCR-sequencing and Campylobacter cultivation.

RESULTS

A significantly higher prevalence of C. concisus in colonic biopsies of patients with CD (53%) was detected as compared with the controls (18%). Campylobacter genus-PCR positivity and C. concisus positivity in patients with UC were 85% and 77% respectively, being significantly higher than that in the controls (48% and 36%). C. concisus was more often detected in descending colonic and rectal biopsies from patients with IBD in comparison to the controls. C. concisus was isolated from patients with IBD.

CONCLUSION

The high intestinal prevalence of C. concisus in patients with IBD, particularly in the proximal large intestine, suggests that future studies are needed to investigate the possible involvement of C. concisus in a subgroup of human IBD. To our knowledge, this is the first report of the association between adult CD and C. concisus as well as the first study of the preferential colonization sites of C. concisus in the human intestine.

Oral and fecal Campylobacter concisus strains perturb barrier function by apoptosis induction in HT-29/B6 intestinal epithelial cells

Campylobacter concisus infections of the gastrointestinal tract can be accompanied by diarrhea and inflammation, whereas colonization of the human oral cavity might have a commensal nature. We focus on the pathophysiology of C. concisus and the effects of different clinical oral and fecal C. concisus strains on human HT-29/B6 colon cells. Six oral and eight fecal strains of C. concisus were isolated. Mucus-producing HT-29/B6 epithelial monolayers were infected with the C. concisus strains. Transepithelial electrical resistance (R^t) and tracer fluxes of different molecule size were measured in Ussing chambers. Tight junction (TJ) protein expression was determined by Western blotting, and subcellular TJ distribution was analyzed by confocal laser-scanning microscopy. Apoptosis induction was examined by TUNEL-staining and Western blot of caspase-3 activation. All strains invaded confluent HT-29/B6 cells and impaired epithelial barrier function, characterized by a time- and dose-dependent decrease in R^t either after infection from the apical side but even more from the basolateral compartment. TJ protein expression changes were sparse, only in apoptotic areas of infected monolayers TJ proteins were redistributed. Solely the barrier-forming TJ protein claudin-5 showed a reduced expression level to 66±8% (P<0.05), by expression regulation from the gene. Concomitantly, Lactate dehydrogenase release was elevated to 3.1±0.3% versus 0.7±0.1% in control (P<0.001), suggesting cytotoxic effects. Furthermore, oral and fecal C. concisus strains elevated apoptotic events to 5-fold. C. concisus-infected monolayers revealed an increased permeability for 332 Da fluorescein (1.74±0.13 vs. 0.56±0.17 10⁻⁶ cm/s in control, P<0.05) but showed no difference in permeability for 4 kDa FITC-dextran (FD-4). The same was true in camptothecin-exposed monolayers, where camptothecin was used for apoptosis induction.

In conclusion, epithelial barrier dysfunction by oral and fecal C. concisus strains could mainly be assigned to apoptotic leaks together with moderate TJ changes, demonstrating a leak-flux mechanism that parallels the clinical manifestation of diarrhea.

Sequencing and validation of the genome of a Campylobacter concisus reveals intra-species diversity

Campylobacter concisus is an emerging pathogen of the human gastrointestinal tract. Its role in different diseases remains a subject of debate; this may be due to strain to strain genetic variation. Here, we sequence and analyze the genome of a C. concisus from a biopsy of a child with Crohn's disease (UNSWCD); the second such genome for this species. A 1.8 Mb genome was assembled with paired-end reads from a next-generation sequencer. This genome is smaller than the 2.1 Mb C. concisus reference BAA-1457. While 1593 genes were conserved across UNSWCD and BAA-1457, 138 genes from UNSWCD and 281 from BAA-1457 were unique when compared against the other. To further validate the genome assembly and annotation, comprehensive shotgun proteomics was performed. This confirmed 78% of open reading frames in UNSWCD and, importantly, provided evidence of expression for 217 proteins previously defined as 'hypothetical' in Campylobacter. Substantial functional differences were observed between the UNSWCD and the reference strain. Enrichment analysis revealed differences in membrane proteins, response to stimulus, molecular transport and electron carriers. Synteny maps for the 281 genes not present in UNSWCD identified seven functionally associated gene clusters. These included one associated with the CRISPR family and another which encoded multiple restriction endonucleases; these genes are all involved in resistance to phage attack. Many of the observed differences are consistent with UNSWCD having adapted to greater surface interaction with host cells, as opposed to BAA-1457 which may prefer a free-living environment.

Detection of Campylobacter concisus and other Campylobacter species in colonic biopsies from adults with ulcerative colitis

INTRODUCTION

The critical role of bacteria in the pathogenesis of ulcerative colitis (UC) is well recognized, but an individual causative microorganism has not been singled out so far. Campylobacter concisus and other non-jejuni species of Campylobacter have been implicated as putative aetiological agents in inflammatory bowel disease in children, but such studies have not been addressed in adults. This study investigated the prevalence of Campylobacter species in colonic biopsy samples from adults with UC and healthy controls.

METHODS

Adult patients who were undergoing diagnostic colonoscopy were recruited for the study, which included 69 patients with histologically proven UC and 65 healthy controls. DNA was extracted from the biopsy samples and subjected to Campylobacter genus specific and Campylobacter concisus specific polymerase chain reaction and sequencing.

RESULTS

Detection of all Campylobacter DNA utilising genus specific primers was significantly higher in cases of UC, with a prevalence of 73.9% (51/69) compared to 23.1% (15/65) in controls (p = 0.0001). Nested PCR for C. concisus DNA was positive in 33.3% (23/69) of biopsy samples from subjects with UC, which was significantly higher than the prevalence rate of 10.8% (7/65) from controls (p = 0.0019). Sequencing of the remaining Campylobacter positive samples revealed that Campylobacter ureolyticus was positive in 21.7% (15/69) of samples from UC subjects as opposed to 3.1% (2/65) in controls (p = 0.0013). Mixed Campylobacter species were more common in UC patients, 20.3% (14/69) as compared to controls 4.6% (3/65) (p = 0.0084).

CONCLUSION

The higher prevalence of Campylobacter genus and more specifically C. concisus and C. ureolyticus in biopsy samples from adults with UC suggests these genera of bacteria may be involved in the chronic inflammation that is characteristically seen in UC. To the best of our knowledge this is the first report of this association of C. concisus and C. ureolyticus with UC in adults.

Emerging thermotolerant Campylobacter species in healthy ruminants and swine

Campylobacters other than Campylobacter jejuni or C. coli were isolated in 35% of 343 farms recently analyzed in northern Spain. This study was aimed at identifying at the species level the 120 isolates collected (21 ovine, 52 beef cattle, 44 dairy cattle, and 3 porcine) by species-specific polymerase chain reaction and 16S rRNA gene sequencing analysis. Thus, five species were identified: Campylobacter hyointestinalis (90 isolates), Campylobacter lanienae (12), Campylobacter fetus subsp. fetus (10), Campylobacter lari (1), and Campylobacter sputorum (1). Ambiguous results were obtained for six isolates. Phylogenetic analyses of the 16S rRNA gene sequence placed three of them (cattle isolates) as an intermediate clade between C. hyointestinalis subsp. hyointestinalis and C. fetus, two ovine isolates formed a new clade clustering with Campylobacter concisus despite sharing higher similarity with Campylobacter mucosalis, and one porcine isolate shared similarly high homology with C. lanienae and C. hyointestinalis subsp. lawsonii. C. hyointestinalis was the predominant species, particularly in cattle, but it was also isolated from sheep and swine. C. lanienae was only found in sheep, C. fetus in cattle and sheep, and C. lari in a single dairy cattle farm. Although previously reported, the isolation of C. lari from cattle is not common, and this is the first report of C. lanienae and C. hyointestinalis in sheep. This study demonstrated the wide distribution in livestock of several emerging zoonotic Campylobacter species and provided valuable information on their host animal reservoirs.

Comparative genotypic and pathogenic examination of Campylobacter concisus isolates from diarrheic and non-diarrheic humans

Background

Campylobacter concisus is an emerging enteric pathogen, yet it is commonly isolated from feces and the oral cavities of healthy individuals. This genetically complex species is comprised of several distinct genomospecies which may vary in pathogenic potential.

Results

We compared pathogenic and genotypic properties of C. concisus fecal isolates from diarrheic and healthy humans residing in the same geographic region. Analysis of amplified fragment length polymorphism (AFLP) profiles delineated two main clusters. Isolates assigned to AFLP cluster 1 belonged to genomospecies A (based on genomospecies-specific differences in the 23S rRNA gene) and were predominantly isolated from healthy individuals. This cluster also contained a reference oral strain. Isolates assigned to this cluster induced greater expression of epithelial IL-8 mRNA and more frequently contained genes coding for the zonnula occludins toxin and the S-layer RTX. Furthermore, isolates from healthy individuals induced greater apoptotic DNA fragmentation and increased metabolic activity than those from diarrheic individuals, and isolates assigned to genomospecies A (of which the majority were from healthy individuals) exhibited higher haemolytic activity compared to genomospecies B isolates. In contrast, AFLP cluster 2 was predominated by isolates belonging to genomospecies B and those from diarrheic individuals. Isolates from this cluster displayed greater mean epithelial invasion and translocation than cluster 1 isolates.

Conclusion

Two main genetically distinct clusters (i.e., genomospecies) were identified among C. concisus fecal isolates from healthy and diarrheic individuals. Strains within these clusters differed with respect to clinical presentation and pathogenic properties, supporting the hypothesis that pathogenic potential varies between genomospecies. ALFP cluster 2 isolates were predominantly from diarrheic patients, and exhibited higher levels of epithelial invasion and translocation, consistent with known roles for these factors in diarrhoeal disease. Conversely, isolates from healthy humans and AFLP cluster 1 or genomospecies A (which were predominantly isolated from healthy humans) exhibited increased haemolytic ability, apoptotic DNA fragmentation, IL-8 induction, and/or carriage of toxin genes. Given that this cluster contains an oral reference strain, it is possible that some of the AFLP cluster 1 isolates are periodontal pathogens and may cause disease, albeit via a different mechanism than those from AFLP cluster 2.

The role of bacteria and pattern-recognition receptors in Crohn's disease

Crohn's disease is widely regarded as a multifactorial disease, and evidence from human and animal studies suggests that bacteria have an instrumental role in its pathogenesis. Comparison of the intestinal microbiota of patients with Crohn's disease to that of healthy controls has revealed compositional changes. In most studies these changes are characterized by an increase in the abundance of Bacteroidetes and Proteobacteria and a decrease in that of Firmicutes. In addition, a number of specific mucosa-associated bacteria have been postulated to have a role in Crohn's disease, including Mycobacterium avium subspecies paratuberculosis, adherent and invasive Escherichia coli, Campylobacter and Helicobacter species. The association between mutations in pattern-recognition receptors (Toll-like receptors and Nod-like receptors) and autophagy proteins and Crohn's disease provides further evidence to suggest that defective sensing and killing of bacteria may drive the onset of disease. In this Review, we present recent advances in understanding the role of bacteria and the contribution of pattern-recognition receptors and autophagy in the pathogenesis of Crohn's disease.

Isolation and detection of Campylobacter concisus from saliva of healthy individuals and patients with inflammatory bowel disease

The presence of Campylobacter concisus in the saliva of healthy individuals and patients with inflammatory bowel disease (IBD) was examined. C. concisus was detected in 97% of the healthy individuals and 100% of the patients with IBD tested. The C. concisus culture positivity rate in younger children was significantly lower than that in the other age groups.

Campylobacter concisus and other Campylobacter species in children with newly diagnosed Crohn's disease

BACKGROUND

Campylobacter concisus and other members of the Campylobacter genus have recently been suggested as possible etiological agents of Crohn's disease (CD). To further investigate this issue we determined the prevalence of these organisms in pediatric patients newly diagnosed with CD.

METHODS

DNA was extracted from fecal specimens collected from 54 children with CD, 27 noninflammatory bowel disease (non-IBD), and 33 healthy controls and subjected to polymerase chain reaction (PCR) sequencing.

RESULTS

Detection of C. concisus DNA using a newly developed PCR assay targeting the 16S rRNA gene of C. concisus showed that 65% (35/54) of fecal samples from CD children were positive, a prevalence significantly higher than that in the healthy (33%, 11/33, P = 0.008) and non-IBD controls (37%, 10/27, P = 0.03). The prevalence of all Campylobacter DNA using genus-specific primers in children with CD was 72% (39/54), which was significantly higher than the 30% (10/33, P = 0.0002) and 30% (8/27, P = 0.0003) observed in healthy and non-IBD controls, respectively.

CONCLUSIONS

Given the strengthening evidence for a significantly higher prevalence of C. concisus and other non-jejuni Campylobacter species in pediatric CD, investigation into the role of these non-jejuni Campylobacter species in the initiation of human IBD is clearly a priority.

The secretome of Campylobacter concisus

A higher prevalence of Campylobacter concisus and higher levels of IgG antibodies specific to C. concisus in Crohn's disease patients than in controls were recently detected. In this study, 1D and 2D gel electrophoresis coupled with LTQ FT-MS and QStar tandem MS, respectively, were performed to characterize the secretome of a C. concisus strain isolated from a Crohn's disease patient. Two hundred and one secreted proteins were identified, of which 86 were bioinformatically predicted to be secreted. Searches were performed on the genome of C. concisus strain 13826, and 25 genes that have been associated with virulence or colonization in other organisms were identified. The zonula occludens toxin was found only in C. concisus among the Campylobacterales, although expanded searches revealed that this protein was present in two epsilon-proteobacterial species from extreme marine environments. Alignments and structural threading indicated that this toxin shared features with that of other virulent pathogens, including Neisseria meningitidis and Vibrio cholerae. Further comparative analyses identified several associations between the secretome of C. consisus and putative virulence factors of this bacterium. This study has identified several factors putatively associated with disease outcome, suggesting that C. concisus is a pathogen of the gastrointestinal tract.

Emerging infections of the gastrointestinal tract

Infections account for significant GI morbidity and mortality worldwide. New organisms are being identified, associated with diarrhoeal illness and some with other gastrointestinal illness as well. Among GI viruses, Sapovirus is now recognised to cause diarrhoea, especially in children. A hypervirulent strain of Clostridium difficile has caused epidemics in many countries. Newly identified bacterial species that may cause diarrhoea include Campylobacter concisus, Arcobacteria, Edwardsiella tarda, Aeromonas, Plesiomonas and Laribacter. Helicobacteria are reviewed, as well as the role of gastric acid suppression in predisposing to enteric infections.

Detection and isolation of Campylobacter species other than C. jejuni from children with Crohn's disease

The presence of Campylobacter species other than Campylobacter jejuni and antibodies to Campylobacter concisus in children were investigated. A significantly greater presence of C. concisus and higher levels of antibodies to C. concisus were detected in children with Crohn's disease (CD) than in controls. Campylobacter species other than C. jejuni were isolated from intestinal biopsy specimens of children with CD.

First attempt to produce experimental Campylobacter concisus infection in mice

AIM: To infect mice with atypical Campylobacter concisus (C. concisus) for the first time.

METHODS: Three separate experiments were conducted in order to screen the ability of five clinical C. concisus isolates of intestinal origin and the ATCC 33237 type strain of oral origin to colonize and produce infection in immunocompetent BALB/cA mice. The majority of the BALB/cA mice were treated with cyclophosphamide prior to C. concisus inoculation to suppress immune functions. Inoculation of C. concisus was performed by the gastric route.

RESULTS: C. concisus was isolated from the liver, ileum and jejunum of cyclophosphamide-treated mice in the first experiment. No C. concisus strains were isolated in the two subsequent experiments. Mice infected with C. concisus showed a significant loss of body weight from day two through to day five of infection but this decreased at the end of the first week. Histopathological examination did not consistently find signs of inflammation in the gut, but occasionally microabscesses were found in the liver of infected animals.

CONCLUSION: Transient colonization with C. concisus was observed in mice with loss of body weight. Future studies should concentrate on the first few days after inoculation and in other strains of mice.

The contribution of cytolethal distending toxin to bacterial pathogenesis

Cytolethal distending toxin (CDT) is a bacterial toxin that initiates a eukaryotic cell cycle block at the G2 stage prior to mitosis. CDT is produced by a number of bacterial pathogens including: Campylobacter species, Escherichia coli, Salmonella enterica serovar Typhi, Shigella dystenteriae, enterohepatic Helicobacter species, Actinobacillus actinomycetemcomitans (the cause of aggressive periodontitis), and Haemophilus ducreyi (the cause of chancroid). The functional toxin is composed of three proteins; CdtB potentiates a cascade leading to cell cycle block, and CdtA and CdtC function as dimeric subunits, which bind CdtB and delivers it to the mammalian cell interior. Once inside the cell, CdtB enters the nucleus and exhibits a DNase I-like activity that results in DNA double-strand breaks. The eukaryotic cell responds to the DNA double-strand breaks by initiating a regulatory cascade that results in cell cycle arrest, cellular distension, and cell death. Mutations in CdtABC that cause any of the three subunits to lose function prevent the bacterial cell from inducing cytotoxicity. The result of CDT activity can differ somewhat depending on the eukaryotic cell types affected. Epithelial cells, endothelial cells, and keratinocytes undergo G2 cell cycle arrest, cellular distension, and death; fibroblasts undergo G1 and G2 arrest, cellular distension, and death; and immune cells undergo G2 arrest followed by apoptosis. CDT contributes to pathogenesis by inhibiting both cellular and humoral immunity via apoptosis of immune response cells, and by generating necrosis of epithelial-type cells and fibroblasts involved in the repair of lesions produced by pathogens resulting in slow healing and production of disease symptoms. Thus, CDT may function as a virulence factor in pathogens that produce the toxin.

The use of (GTG)5 oligonucleotide as an RAPD primer to type Campylobacter concisus

AIM

DNA fingerprinting using (GTG)(5) oligonucleotide as a primer in a random amplified polymorphic DNA (RAPD) assay was assessed by typing isolates of Campylobacter concisus strains, collected over a period of 8 years.

METHODS AND RESULTS

RAPD analysis using the (GTG)(5) oligonucleotide as a primer was used to type 100 isolates of C. concisus comprising mostly isolates from children with diarrhoea. Using this method, 86% of the isolates were found to be genotypically diverse. Of these heterogeneous isolates, 25 of the strains were also shown to be genetically distinct in a previous study using pulsed field gel electrophoresis. The remaining isolates (14) could be classified into five profile groups based on the DNA fingerprinting patterns. The assay successfully identified epidemiologically linked strains from the unrelated genetically diverse pool of strains.

CONCLUSIONS

Laboratory RADP typing using the (GTG)(5) primer proved to be useful in distinguishing related strains of C. concisus from a large pool of unrelated strains of this organism.

SIGNIFICANCE AND IMPACT OF THE STUDY

RAPD typing using (GTG)(5) is a simple method that could be used to investigate the epidemiology of C. concisus. The results suggest that homologous lineages of C. concisus may exist within an otherwise heterogeneous species complex. However, these data need to be confirmed using a more robust typing method.

Antimicrobial susceptibility of clinical isolates of non-jejuni/coli campylobacters and arcobacters from Belgium

OBJECTIVES

To determine the susceptibility of non-jejuni/coli campylobacters and arcobacters isolated from diarrhoeal stool specimens in Belgium.

METHODS

The MICs were determined using Etest for six antimicrobial agents including ampicillin, erythromycin, nalidixic acid, ciprofloxacin, gentamicin and tetracycline for the most frequently isolated non-jejuni/coli campylobacter and arcobacter strains in two University Hospital laboratories between 1995 and 2005.

RESULTS

In total, 85 Campylobacter upsaliensis, 20 Campylobacter concisus, 11 Campylobacter fetus, 61 Arcobacter butzleri and 10 Arcobacter cryaerophilus isolates were tested. Most C. upsaliensis strains were susceptible to ampicillin (100%), gentamicin (100%), ciprofloxacin (94.1%) and tetracycline (100%), whereas 11.8 and 12.9% were resistant to nalidixic acid and erythromycin, respectively. For A. butzleri, 78.7% of isolates were susceptible to ampicillin and erythromycin. Most A. butzleri isolates were susceptible to ciprofloxacin (96.7%), nalidixic acid (82.0%), gentamicin (100%) and tetracycline (100%). All C. concisus strains were fully susceptible to ampicillin and tetracycline, but 5% of them were resistant to gentamicin, ciprofloxacin and erythromycin. Nearly all C. fetus and A. cryaerophilus strains were susceptible to erythromycin but the results should be interpreted with caution since only a small number of strains were tested.

CONCLUSIONS

Fluoroquinolones should be considered in the treatment of severe C. upsaliensis and A. butzleri infection. When clinically indicated, erythromycin remains the first choice for the treatment of intestinal campylobacteriosis caused by C. concisus and C. fetus.

Delineation of Campylobacter concisus genomospecies by amplified fragment length polymorphism analysis and correlation of results with clinical data

Campylobacter concisus has been as frequently isolated from human diarrhea as the important enteropathogen Campylobacter jejuni, but it also occurs in the feces of healthy individuals. The role of C. concisus in human disease has been difficult to determine, since the species comprises at least two phenotypically indistinguishable but genetically distinct taxa (i.e., genomospecies) that may vary in pathogenicity. We examined 62 C. concisus strains by amplified fragment length polymorphism (AFLP) profiling and correlated the results with clinical data. All C. concisus strains gave unique AFLP profiles, and numerical analysis of these data distributed the strains among four clusters. The clustering was of taxonomic significance: two clusters contained, respectively, the type strain (of oral origin) and a reference strain (from diarrhea) of each of the known genomospecies. Genomospecies 2 strains were more frequently isolated from immunocompetent patients and/or patients without concomitant infections that presented with fever, chronic diarrhea, and gut inflammation than was genomospecies 1, clustering with the type strain of oral origin. Bloody diarrhea was recorded only with C. concisus genomospecies 2 infections. We identified two additional C. concisus genomospecies: genomospecies 3 comprised a single strain from an immunocompetent patient, and genomospecies 4 contained five isolates from severely immunodeficient patients, i.e., organ transplantation recipients or those with hematological malignancies. All genomospecies 4 strains were of the same protein profile group and failed to react with a C. concisus species-specific PCR assay based on 23S rRNA gene sequences: the taxonomic position of this group requires closer investigation. Campylobacter concisus is genetically and taxonomically diverse and contains at least four distinct genomospecies that may exhibit differences in their spectra of virulence potential.

Campylobacter concisus: an emerging pathogen?

Only about half the cases of intestinal infectious disease have a routinely detectable causative agent diagnosed. Increasingly, evidence indicates that Campylobacter species other than C. jejuni and C. coli are associated with such cases. However, evidence is less clear, from epidemiological studies, for the pathogenic nature of these unusual campylobacters. This is particularly true for organisms like C. concisus and is compounded by poor methods for routine recovery and identification. Moreover, the application of typing methods for C. concisus has indicated a heterogeneous population and there is preliminary evidence to suggest differences in the pathogenic potential of strain types. However, considerable further work is needed with more discriminatory genotyping methods, before accurate assessment of the risk of C. concisus infection to human health can be determined.