Serological investigation into the association between Streptococcus bovis and colonic cancer

A Narrative Literature Review on Sepsis: A Primary Manifestation of Colorectal Neoplasm

Sepsis and colorectal cancer (CRC) exhibit a complex relationship that warrants further exploration. This review delves into the interplay of factors between sepsis and CRC, uncovering shared pathophysiological traits and potential bacterial associations. Understanding these connections could pave the way for earlier diagnosis, improved management, and enhanced outcomes in CRC patients. The role of immune system dysfunction, hypoalbuminemia, and specific microbial imbalances, such as Streptococcus bovis and Clostridium septicum, are discussed. Recognizing sepsis in CRC patients is crucial for timely intervention, and tailored approaches encompassing antibiotic therapy, source control measures, and cancer treatment are essential for comprehensive care. Monitoring biomarkers and ratios can provide valuable insights into complications and overall health outcomes. A multidisciplinary approach involving various specialists is necessary to address the global burden of CRC and its association with sepsis while exploring novel interventions, such as fecal microbiota transplantation and personalized care. We conducted a thorough search using reputable databases such as PubMed, Scopus, and Google Scholar to investigate the connection between sepsis and CRC. We refined our search terms, utilized sidebar filters, and examined references in selected articles. This meticulous process helped us create a comprehensive literature review and gain valuable insights into this relationship.

Roles of gut microbiota in colorectal carcinogenesis providing a perspective for early diagnosis and treatment

Colorectal cancer (CRC) is the third most prevalent malignant neoplasm in the world. CRC is influenced by both environmental and genetic factors. Through toxin-mediated DNA damage and promotion of persistent dysregulated inflammation, the gut microbiota plays a crucial role in the development of CRC. In this review, we discussed the correlation between the bacterial microbiota and CRC carcinogenesis as well as the mechanism by which Streptococcus bovis/gallolyticus, Fusobacterium nucleatum, Bacteroides fragilis, and Escherichia coli can cause CRC.

The Road to Infection: Host-Microbe Interactions Defining the Pathogenicity of Streptococcus bovis/Streptococcus equinus Complex Members

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) comprises several species inhabiting the animal and human gastrointestinal tract (GIT). They match the pathobiont description, are potential zoonotic agents and technological organisms in fermented foods. SBSEC members are associated with multiple diseases in humans and animals including ruminal acidosis, infective endocarditis (IE) and colorectal cancer (CRC). Therefore, this review aims to re-evaluate adhesion and colonization abilities of SBSEC members of animal, human and food origin paired with genomic and functional host-microbe interaction data on their road from colonization to infection. SBSEC seem to be a marginal population during GIT symbiosis that can proliferate as opportunistic pathogens. Risk factors for human colonization are considered living in rural areas and animal-feces contact. Niche adaptation plays a pivotal role where Streptococcus gallolyticus subsp. gallolyticus (SGG) retained the ability to proliferate in various environments. Other SBSEC members have undergone genome reduction and niche-specific gene gain to yield important commensal, pathobiont and technological species. Selective colonization of CRC tissue is suggested for SGG, possibly related to increased adhesion to cancerous cell types featuring enhanced collagen IV accessibility. SGG can colonize, proliferate and may shape the tumor microenvironment to their benefit by tumor promotion upon initial neoplasia development. Bacteria cell surface structures including lipotheichoic acids, capsular polysaccharides and pilus loci (pil1, pil2, and pil3) govern adhesion. Only human blood-derived SGG contain complete pilus loci and other disease-associated surface proteins. Rumen or feces-derived SGG and other SBSEC members lack or harbor mutated pili. Pili also contribute to binding to fibrinogen upon invasion and translocation of cells from the GIT into the blood system, subsequent immune evasion, human contact system activation and collagen-I-binding on damaged heart valves. Only SGG carrying complete pilus loci seem to have highest IE potential in humans with significant links between SGG bacteremia/IE and underlying diseases including CRC. Other SBSEC host-microbe combinations might rely on currently unknown mechanisms. Comparative genome data of blood, commensal and food isolates are limited but required to elucidate the role of pili and other virulence factors, understand pathogenicity mechanisms, host specificity and estimate health risks for animals, humans and food alike.

Biofilm formation and transcriptome analysis of Streptococcus gallolyticus subsp. gallolyticus in response to lysozyme

Streptococcus gallolyticus subsp. gallolyticus is a commensal bacterium of the human gastrointestinal tract, and a pathogen causing infective endocarditis and other biofilm-associated infections via exposed collagen. This study focuses on the characterization of the biofilm formation and collagen adhesion of S. gallolyticus subsp. gallolyticus under different conditions. In this study, it has been observed that the isolate UCN 34 is resistant to 20 mg/ml lysozyme in BHI medium, whereas the strain BAA-2069 builds more biofilm in the presence of lysozyme compared to in a control of BHI without lysozyme. A transcriptome analysis with whole genome microarrays of these two isolates in BHI medium with lysozyme compared to control without lysozyme revealed changes in gene expression levels. In the isolate BAA-2069, 67 genes showed increased expression in the presence of lysozyme, while in the isolate UCN 34, 165 genes showed increased expression and 30 genes showed decreased expression through lysozyme treatment. Products of genes which were higher expressed are in involved in transcription and translation, in cell-wall modification, in hydrogen peroxide resistance and in bacterial immunity. Furthermore, the adhesion ability of different strains of S. gallolyticus subsp. gallolyticus to collagen type I and IV was analyzed. Thereby, we compared the adhesion of 46 human isolates with 23 isolates from animals. It was shown that the adhesion ability depends significantly on whether the isolate was isolated from human or animal. For example, high adhesion ability was observed for strain UCN 34 isolated from an infective endocarditis patient, whereas strain DSM 16831 isolated from koala feces adhered only marginally to collagen. Full genome microarray analysis of these two strains revealed strain-dependent gene expression due to adhesion. The expression of 25 genes of a transposon and 15 genes of a phage region in strain DSM 16831 were increased, which corresponds to horizontal gene transfer. Adherence to collagen in strain UCN 34 led to higher expression of 27 genes and lower expression of 31 genes. This was suggestive of a change in nutrient uptake.

Transcriptome analysis of Streptococcus gallolyticus subsp. gallolyticus in interaction with THP-1 macrophage-like cells

BACKGROUND

Streptococcus gallolyticus subsp. gallolyticus (S. gallolyticus) is a pathogen of infective endocarditis. It was observed previously that this bacterium survives longer in macrophages than other species and the phagocytic uptake by and survival in THP-1 macrophages is strain-dependent.

METHODS

The phagocytosis assay was performed with THP-1 macrophages. S. gallolyticus specific whole genome microarrays were used for transcriptome analysis.

RESULTS

Better survival in macrophages was observed for UCN34, BAA-2069 and ATCC43143 than for DSM16831 and LMG17956. S. gallolyticus strains show high resistance to tested bactericidal agents (acid, lysozyme and hydrogen peroxide). S. gallolyticus stimulates significant lower cytokine gene expression and causes less lysis of macrophages compared to the control strain Staphylococcus aureus. S. gallolyticus reacts to oxidative burst with a higher gene expression of NADH oxidase initially at the early phase. Expression of genes involved in D-alanylation of teichoic acid, carbohydrate metabolism and transport systems were upregulated thereafter.

CONCLUSION

S. gallolyticus is very resistant to bactericidal agents normally causing degradation of bacteria in phagolysosomes. Additionally, the D-alanylation of teichoic acid is an important factor for survival.

Streptococcus bovis prosthetic valve endocarditis associated with silent colonic carcinoma

A 75-year-old woman was admitted to our hospital with a 3-month history of fever. Of note, she had a bioprosthetic mitral valve replacement 1 year prior to admission. Streptococcus bovis was isolated from three sets of blood cultures. An echocardiogram showed a flickering mass attached to the bioprosthesis. Her blood culture became sterile by the fourth day of ceftriaxone therapy. In spite of the absence of gastrointestinal symptoms, screening colonoscopy revealed an invasive colonic adenocarcinoma. The association linking S. bovis endocarditis and colonic tumours is well recognised. However, despite early reports of this association by Klein et al in 1979, a large number of practising physicians remain unaware of this phenomenon. This lack of awareness results in lost opportunities for early diagnosis and, consequently, improved outcome in such patients. Our report emphasises this association in an area with a low incidence of S. bovis endocarditis.

Gut microbiota, inflammation and colorectal cancer

Although genes contribute to colorectal cancer, the gut microbiota are an important player. Accumulating evidence suggests that chronic infection and the ensuing inflammation contributes to tumor initiation and tumor progression. A variety of bacterial species and tumor-promoting virulence mechanisms have been investigated. Significant advances have been made in understanding the composition and functional capabilities of the gut microbiota and its roles in cancer. In the current review, we discuss the novel roles of microbiota in the progression of colon cancer. Although microbiota technically include organisms other than bacteria e.g., viruses and fungi, this review will primarily focus on bacteria. We summarize epidemiological studies of human microbiome and colon cancer. We discuss the progress in the scientific understanding of the interplay between the gut microbiota, barrier function, and host responses in experimental models. Further, we discuss the potential application in prevention, diagnosis, and therapy of colon cancer by targeting microbiota. We discuss the challenges lie ahead and the future direction in studying gut microbiome in colon cancer to close the gap between the basic sciences and clinical application.

Streptococcus gallolyticus bacteraemia in hepatobiliary-pancreatic and colonic pathologies

BACKGROUND

Streptococcus gallolyticus bacteraemia has been associated with several pathologies, including bacterial endocarditis and colorectal cancer.

AIMS

In this study, we have analysed whether Streptococcus gallolyticus bacteraemia is associated with an increased risk of hepatobiliary and colonic pathology. The association with other pathologies and the antibiotic sensitivities of Streptococcus gallolyticus were also analysed.

DESIGN

Observational retrospective study.

METHODS

The case notes of patients with documented Streptococcus gallolyticus bacteraemia between 2007 and 2012 at Mater Dei hospital (Malta) were reviewed. Demographic and clinical data, including co-morbidities, clinical investigations, antibiotic sensitivities and mortality were analysed.

RESULTS

A total of 42 patients (33 males, 9 females) were recruited. Two patients were pre-term infants and were therefore excluded from the study. Mean age of the cohort population studied was 72 years (SD ± 14). One-year survival rate was 62%. Gastrointestinal (colonic and hepatobiliary-pancreatic) pathologies were present in 59.5% of patients with 16% of this group having more than one gastrointestinal pathology. High incidence rates of underlying diabetes mellitus (28.6%), valvular heart disease (21.4%) and malignancies (21.4%) were noted in this study. Furthermore, we observed that 14.3% of patients had an underlying respiratory pathology. Streptococcus gallolyticus was 100% sensitive to cefotaxime and vancomycin but was highly resistant to clindamycin, erythromycin and tetracycline.

CONCLUSION

Streptococcus gallolyticus bacteraemia is commoner in the elderly and in those with multiple underlying co-morbidities. The high incidence of gastrointestinal pathologies among patients with Streptococcus gallolyticus bacteraemia (59.5%) suggests that a thorough work-up for colonic and hepatobiliary/pancreatic pathology should be carried out in these patients.

Colon Macrophages Polarized by Commensal Bacteria Cause Colitis and Cancer through the Bystander Effect

Intestinal commensal bacteria have recently been shown to trigger macrophages to produce diffusible clastogens (or chromosome-breaking factors) through a bystander effect (BSE) that mediates DNA damage and induces chromosomal instability in neighboring cells. Colon macrophages appear central to colon carcinogenesis and BSE through the expression of tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). The former induces netrin-1, a regulator of intestinal epithelial cell apoptosis, and the latter generates trans-4-hydroxy-2-nonenal (4-HNE), an endogenous mutagen. To test whether colon macrophages are key effectors for BSE, we depleted these cells in interleukin-10 knockout mice colonized with Enterococcus faecalis using encapsulated liposomal clodronate (ELC), a bisphosphonate that causes macrophage apoptosis. We observed that E. faecalis polarizes colon macrophages to an M1 phenotype. In addition, depleting these cells suppressed COX-2 and TNF-α, blocked the formation of 4-HNE protein adducts, and inhibited up-regulation of netrin-1-all markers for BSE. Finally, treatment with ELC prevented colitis, β-catenin activation, and cancer formation. These results show that selected human commensals can polarize colon macrophages to the M1 phenotype and, when activated, serve as the key effector for bacterial-induced BSE. Our findings suggest that depleting M1-polarized macro-phages is a mechanism for the chemopreventive activity of bisphosphonates and that it represents a new strategy for preventing colon cancer induced by intestinal commensals.

Significance of infectious agents in colorectal cancer development

Colorectal cancer (CRC) is a major burden to healthcare systems worldwide accounting for approximately one million of new cancer cases worldwide. Even though, CRC mortality has decreased over the last 20 years, it remains the third most common cause of cancer-related mortality, accounting for approximately 600,000 deaths in 2008 worldwide. A multitude of risk factors have been linked to CRC, including hereditary factors, environmental factors and inflammatory syndromes affecting the gastrointestinal tract. Recently, various pathogens were added to the growing list of risk factors for a number of common epithelial cancers, but despite the multitude of correlative studies, only suggestions remain about the possible relationship between selected viruses and bacteria of interest and the CRC risk. United States military service members are exposed to various risk factors impacting the incidence of cancer development. These exposures are often different from that of many sectors of the civilian population. Thereby, cancer risk identification, screening and early detection are imperative for both the military health care beneficiaries and the population as a whole. In this review, we will focus on several pathogens and their potential roles in development of CRC, highlighting the clinical trials evaluating this correlation and provide our personal opinion about the importance of risk reduction, health promotion and disease prevention for military health care beneficiaries.

Gut bacteria in health and disease: a survey on the interface between intestinal microbiology and colorectal cancer

A healthy human body contains at least tenfold more bacterial cells than human cells and the most abundant and diverse microbial community resides in the intestinal tract. Intestinal health is not only maintained by the human intestine itself and by dietary factors, but is also largely supported by this resident microbial community. Conversely, however, a large body of evidence supports a relationship between bacteria, bacterial activities and human colorectal cancer. Symbiosis in this multifaceted organ is thus crucial to maintain a healthy balance within the host-diet-microbiota triangle and accordingly, changes in any of these three factors may drive a healthy situation into a state of disease. In this review, the factors that sustain health or drive this complex intestinal system into dysbiosis are discussed. Emphasis is on the role of the intestinal microbiota and related mechanisms that can drive the initiation and progression of sporadic colorectal cancer (CRC). These mechanisms comprise the induction of pro-inflammatory and pro-carcinogenic pathways in epithelial cells as well as the production of (geno)toxins and the conversion of pro-carcinogenic dietary factors into carcinogens. A thorough understanding of these processes will provide leads for future research and may ultimately aid in development of new strategies for CRC diagnosis and prevention.

Sequencing and comparative genome analysis of two pathogenic Streptococcus gallolyticus subspecies: genome plasticity, adaptation and virulence

Streptococcus gallolyticus infections in humans are often associated with bacteremia, infective endocarditis and colon cancers. The disease manifestations are different depending on the subspecies of S. gallolyticus causing the infection. Here, we present the complete genomes of S. gallolyticus ATCC 43143 (biotype I) and S. pasteurianus ATCC 43144 (biotype II.2). The genomic differences between the two biotypes were characterized with comparative genomic analyses. The chromosome of ATCC 43143 and ATCC 43144 are 2,36 and 2,10 Mb in length and encode 2246 and 1869 CDS respectively. The organization and genomic contents of both genomes were most similar to the recently published S. gallolyticus UCN34, where 2073 (92%) and 1607 (86%) of the ATCC 43143 and ATCC 43144 CDS were conserved in UCN34 respectively. There are around 600 CDS conserved in all Streptococcus genomes, indicating the Streptococcus genus has a small core-genome (constitute around 30% of total CDS) and substantial evolutionary plasticity. We identified eight and five regions of genome plasticity in ATCC 43143 and ATCC 43144 respectively. Within these regions, several proteins were recognized to contribute to the fitness and virulence of each of the two subspecies. We have also predicted putative cell-surface associated proteins that could play a role in adherence to host tissues, leading to persistent infections causing sub-acute and chronic diseases in humans. This study showed evidence that the S. gallolyticus still possesses genes making it suitable in a rumen environment, whereas the ability for S. pasteurianus to live in rumen is reduced. The genome heterogeneity and genetic diversity among the two biotypes, especially membrane and lipoproteins, most likely contribute to the differences in the pathogenesis of the two S. gallolyticus biotypes and the type of disease an infected patient eventually develops.

The association of Streptococcus bovis/gallolyticus with colorectal tumors: the nature and the underlying mechanisms of its etiological role

Streptococcus bovis (S. bovis) bacteria are associated with colorectal cancer and adenoma. S. bovis is currently named S. gallolyticus. 25 to 80% of patients with S. bovis/gallolyticus bacteremia have concomitant colorectal tumors. Colonic neoplasia may arise years after the presentation of bacteremia or infectious endocarditis of S. bovis/gallolyticus. The presence of S. bovis/gallolyticus bacteremia and/or endocarditis is also related to the presence of villous or tubular-villous adenomas in the large intestine. In addition, serological relationship of S. gallolyticus with colorectal tumors and direct colonization of S. gallolyticus in tissues of colorectal tumors were found. However, this association is still under controversy and has long been underestimated. Moreover, the etiological versus non-etiological nature of this associationis not settled yet. Therefore, by covering the most of up to date studies, this review attempts to clarify the nature and the core of S. bovis/gallolyicus association with colorectal tumors and analyze the possible underlying mechanisms.

Infectious causes of colorectal cancer

Colorectal cancer is a major cause of cancer-related morbidity and mortality in the United States and many other regions of the world. Our understanding of the pathogenesis of colorectal cancer, from the precursor adenomatous polyp to adenocarcinoma, has evolved rapidly. Colorectal carcinogenesis is a sequential process characterized by the accumulation of multiple genetic and molecular alterations in colonic epithelial cells. However, the development of colorectal cancer involves more then just a genetic predisposition. External or environmental factors presumably play a significant role, and inflammatory bowel diseases, obesity, alcohol consumption, and a diet high in fat and low in fiber have all been implicated as risk factors for the development of either colonic adenomas or carcinomas. We are becoming increasingly aware of microbes as causes of malignancies. This article reviews the various microbes that have been associated with the development of colorectal carcinomas.

Involvement of two-component signal transduction system, ComDE, in the regulation of growth and genetic transformation, in the ruminal bacterium Streptococcus bovis

In ruminants, Streptococcus bovis is considered to be associated with acute rumen acidosis. To elucidate the regulatory mechanisms of S. bovis growth, we investigated the function of the two components of the peptide pheromone-signaling system, ComD and ComE, which are encoded by comD and comE, respectively, via the competence-stimulating peptide ComC, which is encoded by comC. Deletion of entire comC and two-thirds of comD resulted in decreased growth rate, which may be related to the change in the expression of several proteins, as shown by two-dimensional gel electrophoresis. The transcript level of comED was decreased by the disruption of comCD, suggesting that the transcription of comED might be stimulated by ComC. The transformation frequency was decreased by the disruption of comCD. Addition of recombinant ComC to S. bovis cultures increased the growth rate and transformation frequency. In the cultures of mixed ruminal microbes, addition of mature ComC peptide increased the number of S. bovis per total bacterial counts as estimated by the cDNA amounts of 16SrRNA. Thus, the peptide pheromone-signaling system via ComC, D, and E might be involved in the control of S. bovis growth in addition to competence development. This is the first report suggesting that an autoinducing peptide functions in the ruminal ecosystem.

Streptococcus bovis endocarditis, a silent sign for colonic tumour

AIM

An association between colonic carcinoma and Streptococcus bovis endocarditis/bacteraemia was first suggested in 1951. This knowledge has great clinical implications, yet we found scant awareness amongst general surgical trainees. The aim of this article was to review the evidence available in the literature and explore the pathophysiology behind this association.

METHOD

The literature was reviewed, between 1950 and 2008, using Pubmed, Embase and Ovid database searches. We utilized different combinations of the keywords: Streptococcus bovis, endocarditis, septicaemia and colon cancer/carcinoma. Quality assessment was determined using the Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001). Studies were selected based on their relevance to the aims to be addressed.

RESULTS

We included nine case reports and found 24 studies demonstrating an association between S. bovis bacteraemia/endocarditis and colon cancer; the reported incidence in studies was variable (6-67%). The majority of studies (20) were retrospective analysis of data; only four studies were prospective. A total of 12 of 24 studies also reported an association with extra-colonic malignancy (1-22%) and 12 with liver disease (3-57%). Eight studies relevant to the pathophysiology of this association were identified.

CONCLUSION

Streptococcus bovis endocarditis and/or bacteraemia is an early clue to the likely presence of colorectal cancer. Whilst further studies are required to determine the precise pathophysiology, clinicians should be aware of this association. It is advisable to investigate rigorously for colon cancer in all patients presenting with S. bovis endocarditis/bacteraemia; such patients may also present with liver disease or, occasionally, extra-colonic malignancy.

Gastric dysplasia may be an independent risk factor of an advanced colorectal neoplasm

AIM: To evaluate the relationship between gastric dysplasia and Helicobacter pylori (H pylori) and the occurrence of colorectal adenoma, and to define the necessity for colonoscopy in patients with gastric dysplasia or H pylori infection.

METHODS: From May 2005 to February 2008, 133 patients with established gastric dysplasia by gastroduodenoscopy (EGD) were additionally investigated by colonoscopy. The authors compared results with those of 213 subjects who underwent both EGD and colonoscopy during the same period at the author’s Health Promotion Center as a control group. H pylori infection was evaluated in both the gastric dysplasia and control groups.

RESULTS: The mean age of all 346 study subjects was 54.1 ± 10.5 years, and there were 258 (73%) men and 87 (27%) women. No significant difference was found between the H pylori positive and negative subjects in terms of the prevalence of colorectal adenoma and advanced colorectal adenoma (P = 0.261). Patients with gastric dysplasia showed no elevated risk of colorectal adenoma (OR = 0.910, 95% CI: 0.587-1.411, P = 0.738), but had a significantly higher risk of having advanced colorectal adenoma (OR = 3.382, 95% CI: 1.700-6.342, P = 0.000).

CONCLUSION: The study emphasizes the need for colon surveillance in patients with gastric dysplasia, regardless of H pylori infection.

Investigation into the controversial association of Streptococcus gallolyticus with colorectal cancer and adenoma

Background

The seroprevalence of IgG antibodies of Streptococcus gallolyticus subspecies gallolyticus, CIP 105428, was evaluated to investigate the controversial association of S. gallolyticus with colorectal carcinoma and adenoma in attempt to investigate the nature of such association if any, by exploring the mRNA expression of NF-κB and IL-8. Moreover, the serological behavior of S. gallolyticus IgG antibodies was compared to that of an indicator bacterium of bowel, Bacteroides fragilis.

Methods

ELISA was used to measure IgG antibodies of S. gallolyticus and B. fragilis in sera of 50 colorectal cancer, 14 colorectal adenoma patients, 30 age- and sex- matched apparently healthy volunteers (HV) and 30 age- and sex- matched colonoscopically-proven tumor-free control subjects. NF-κB and IL-8 mRNA expression was evaluated in tumorous and non-tumorous tissue sections of carcinoma and adenoma patients in comparison with that of control subjects by using in situ hybridization assay.

Results

Colorectal cancer and adenoma patients were associated with higher levels of serum S. gallolyticus IgG antibodies in comparison with HV and control subjects (P < 0.05) while no similar association was found with serum IgG antibodies of B. fragilis (P > 0.05). ELISA cutoff value for the seropositivity of S. gallolyticus IgG was calculated from tumor-free control group. The expression of NF-κB mRNA was higher in tumorous than non-tumorous tissue sections of adenoma and carcinoma, higher in carcinoma/adenoma sections than in control subjects, higher in tumorous sections of carcinoma than in adenoma patients, and higher in S. gallolyticus IgG seropositive than in seronegative groups in both tumorous and non-tumorous sections (P < 0.05). IL-8 mRNA expression in tumorous sections of adenoma and carcinoma was higher than in non-tumorous sections, higher in carcinoma/adenoma than in control subjects, and higher in S. gallolyticus IgG seropositive than in seronegative groups in tumorous rather than non-tumorous sections (P < 0.05).

Conclusion

S. gallolyticus most likely plays an essential role in the oncogenic progression of normal colorectal mucosa to adenoma and to CRC. This promoting/propagating role of S. gallolyticus might take place by utilizing certain inflammatory, anti-apoptotic, and angiogenic factors of transformation including NF-κB and IL-8.

Infectious agents and colorectal cancer: a review of Helicobacter pylori, Streptococcus bovis, JC virus, and human papillomavirus

Based on the high volume of bacteria and viruses that the intestine is exposed to and the importance of infectious agents in some gastrointestinal and anogenital cancers, it is not surprising the many studies have evaluated the association between colorectal cancer and infectious agents. This review highlights investigations of four agents in relation to colorectal cancer. Helicobacter pylori, Streptococcus bovis, JC virus, and human papillomavirus have all been evaluated as possible etiologic agents for colorectal cancer. For each of these agents, a review of possible mechanisms for carcinogenesis and epidemiologic evidence is discussed, and future directions for research are proposed.

Ecology and pathogenicity of gastrointestinal Streptococcus bovis

Streptococcus bovis is an indigenous resident in the gastrointestinal tracts of both humans and animals. S. bovis is one of the major causes of bacterial endocarditis and has been implicated in the incidence of human colon cancer, possibly due to chronic inflammatory response at the site of intestinal colonization. Certain feeding regimens in ruminants can lead to overgrowth of S. bovis in the rumen, resulting in the over-production of lactate and capsular polysaccharide causing acute ruminal acidosis and bloat, respectively. There are multiple strategies in controlling acute lactic acidosis and bloat. The incidence of the two diseases may be controlled by strict dietary management. Gradual introduction of grain-based diets and the feeding of coarsely chopped roughage decrease the incidence of the two disease entities. Ionophores, which have been used to enhance feed conversion and growth rate in cattle, have been shown to inhibit the growth of lactic acid bacteria in the rumen. Other methods of controlling lactic acid bacteria in the ruminal environment (dietary supplementation of long-chain fatty acids, induction of passive and active immune responses to the bacteria, and the use of lytic bacteriophages) have also been investigated. It is anticipated that through continued in-depth ecological analysis of S. bovis the characteristics responsible for human and animal pathogenesis would be sufficiently identified to a point where more effective control strategies for the control of this bacteria can be developed.

Profiling the humoral immune response in colon cancer patients: diagnostic antigens from Streptococcus bovis

The human bowel contains a large and dynamic bacterial population that is not only essential for intestinal health, but also critical for the development of diseases such as cancer. In this respect, the Gram-positive bacterium Streptococcus bovis has been associated with colon cancer for many years. To investigate the clinical importance of this association, an immunocapture mass spectrometry assay was developed that can generate infection-related protein profiles. The composition of these profiles is governed by the capture of specific antigens by serum antibodies from colon cancer patients. This assay showed that S. bovis antigen profiles could distinguish 11 out of 12 colon cancer patients from 8 control subjects, whereas antigen profiles derived from the gut bacterium Escherichia coli were not diagnostic for colon cancer. Moreover, S. bovis antigen profiles were also detected in polyp patients, indicating that infection with this bacterium does occur early during carcinogenesis. Highly accurate tandem mass spectrometry was used to identify one of the diagnostic antigens as a surface-exposed heparin-binding protein, which might be involved in attachment of S. bovis to tumor cells. Together, these findings corroborate the hypothesis that colonic lesions provide a specific niche for S. bovis, resulting in tumor-associated "silent" infections. These infections, however, only become apparent in colon cancer patients with a compromised immune system (bacteremia) or coincidental cardiac valve lesions (endocarditis). This makes profiling of the humoral immune response against "silent" S. bovis infections a promising diagnostic tool for the early detection of human colon cancer, which is crucial for the effective treatment of this disease.

Infectious endocarditis from Streptococcus bovis associated with colonic carcinoma: case report and literature review

BACKGROUND

Many studies in the literature have warned of the need for investigation of colonic lesions among patients, especially elderly ones, who have bacteremia and/or endocarditis from Streptococcus bovis. Bacteremia and infectious endocarditis from Streptococcus bovis may be related to the presence of neoplastic lesions in the large intestine and hepatic disease.

AIM

This report describes a patient who presented infectious endocarditis from Streptococcus bovis associated with colonic carcinoma and tubular-villous adenomas.

CONCLUSIONS

The finding of this bacterium among patients with septicemia and/or endocarditis is also related to the presence of villous or tubular-villous adenomas in the large intestine. For this reason, complete and detailed investigation of the large intestine must be performed in patients with infectious endocarditis, even in the absence of intestinal symptoms. An increased incidence of this condition or hepatic dysfunction has been reported among patients with infectious endocarditis from Streptococcus bovis. Patients with infectious endocarditis from Streptococcus bovis and normal colonoscopy may be included in the group at risk for developing colonic cancer. The knowledge that there is an association between endocarditis from Streptococcus bovis and carcinoma of the colon has important clinical implications. If the lesion can be discovered at an early stage, curative resection may become possible.

Prospective case-cohort study of intestinal colonization with enterococci that produce extracellular superoxide and the risk for colorectal adenomas or cancer

OBJECTIVE

The aim of this study was to determine whether intestinal colonization with enterococci that produce extracellular superoxide (O2*-), a free radical implicated in the development of colorectal cancer, is associated with these lesions or their precursors.

METHODS

A prospective case-cohort study was performed by isolating enterococci from stools of consecutive patients undergoing colonoscopy who had no prior history of colonoscopy or colorectal cancer. A food frequency questionnaire was also administered to control for dietary factors known to affect the risk for these lesions.

RESULTS

Among 159 evaluable participants were 77 with no precancerous or cancerous pathology, 61 with adenomas <2 cm, 10 with adenomas > or =2 cm, and 11 with cancer. Regression analyses found no associations for those subjects with adenomas of any size or with cancer and colonization with O2*--producing enterococci, any nutrient, or age. For those patients with large adenomas > or = 2 cm or cancer, however, significant associations were noted for age (OR 1.94 per decade, 95% CI 1.2-3.5), beta-carotene (OR 0.44 per 500 microg/1000 kcal/day, 95% CI 0.2-0.8), vitamin A (OR 3.20 per 500 microg/1000 kcal/day, 95% CI 1.2-8.9), and vitamin E (OR 0.09 per 10 mg/ 1000 kcal/day, 95% CI 0.006-0.9), but not colonization with O2*--producing enterococci. Second stools collected 1 yr later, however, often contained dissimilar enterococcal flora, undermining an important study assumption.

CONCLUSIONS

Significant associations were found for those with large adenomas or cancer (but not small adenomas), with age, and with foods enriched for vitamin A, vitamin E, and beta-carotene. An association between colonization with O2*--producing enterococci and colorectal adenomas or cancer, however, could not be ascertained, possibly because intestinal enterococcal flora changes over time, leaving a potentially cohesive hypothesis of colon cancer and risk factors as yet unanswered.

A prospective controlled study of the association of Streptococcus bovis with colorectal carcinoma

AIM

To investigate the ability of Streptococcus bovis to colonise colorectal cancers.

PATIENTS

19 patients with colorectal cancer and 23 controls without malignancy.

SETTING

University teaching hospital.

METHODS

Prospective study comparing unselected patients with known colorectal cancer with age and sex matched controls. Carcinoma tissue from patients with colorectal cancer and normal colonic mucosa, stool, and blood from both patients and control subjects were cultured.

RESULTS

In contrast to published data, the faecal carriage rate was similar in cancer (11%) and control groups (13%).

CONCLUSIONS

Faecal colonisation by Str bovis in colorectal cancer patients is lower than previously reported and does not differ significantly from controls.

Lateral neck abscess caused by Streptococcus bovis in a patient with undiagnosed colon cancer

Bacteraemia or endocarditis caused by Streptococcus bovis, a non-enterococcal group D streptococcus, is a very common finding in patients suffering from intestinal tumours or other colon diseases. A case of a patient with a laternal neck abscess caused by S. bovis is reported. During the treatment the patient was found to have colonic malignant lesions. The problems in the appropriate diagnosis and the possible correlation between these two clinical entities are presented and discussed.

Serum antibodies to commensal oral and gut bacteria vary with age

This study examined the relationship between serum antibody levels to selected bacteria from the commensal oral and gut flora with increased age in a healthy adult population. A total of 116 healthy subjects were studied consisting of the following age groups: 20-39 years (group A), 40-59 years (group B), 60-79 years (group C) and 80+ years (group D). Only significantly lower mean IgM antibody levels to Streptococcus mutans strain Guy's serotype c were observed in older age groups (P < 0.001). With Actinomyces viscosus NCTC 10951 significantly reduced IgM levels (P < 0.02) and significantly elevated IgA levels were observed with increased age (P < 0.05). IgA and IgG antibodies to Escherichia coli NCTC 10418 were increased significantly in the older age groups (P < 0.001), whilst a trend toward lower levels of IgM antibodies was recorded with age. No changes in IgA antibodies to Streptococcus faecalis NCTC 775 were observed but the lowest level of IgM antibodies were detected in the oldest age group (P < 0.05). Mean specific activity was decreased with age with IgM antibodies to the oral bacteria and increased with age with IgG and IgA antibodies to E. coli. Overall, our results suggest a general reduction in serum IgM antibody responses. This impairment in the circulatory IgM immune response may contribute to the increased occurrence of infections in the elderly.

[Comparative analysis of antibiotic sensitivity of Streptococcus pneumoniae strains isolated from patients and carriers]

The data on antibiotic sensitivity of 38 strains of S. pneumoniae isolated from children and 46 strains isolated from carriers are presented. The isolates from the carriers had significantly higher sensitivity to benzylpenicillin, ampicillin, methicillin, oxacillin, cefazolin, erythromycin, oleandomycin and lincomycin. Resistance to gentamicin was more frequent in the strains isolated from the carriers. Among the strains of S. pneumoniae isolated from the patients and carriers representatives of serovar K19 were more frequent. There were no statistically reliable difference in them by sensitivity to benzylpenicillin, ampicillin, cefazolin, lincomycin and rifampicin. Still, the isolates from the carriers were much more sensitive to methicillin, oxacillin, oleandomycin and erythromycin.