Association between bacteremia due to Streptococcus gallolyticus subsp. gallolyticus (Streptococcus bovis I) and colorectal neoplasia: a case-control study

Study of Microbiota Associated to Early Tumors Can Shed Light on Colon Carcinogenesis

An increasingly important role for gut microbiota in the initiation and progression of colorectal cancer (CRC) has been described. Even in the early stages of transformation, i.e., colorectal adenomas, changes in gut microbiota composition have been observed, and several bacterial species, such as pks+Escherichia coli and enterotoxigenic Bacteroides fragilis, have been proposed to drive colon tumorigenesis. In recent years, several strategies have been developed to study mucosa-associated microbiota (MAM), which is more closely associated with CRC development than lumen-associated microbiota (LAM) derived from fecal samples. This review summarizes the state of the art about the oncogenic actions of gut bacteria and compares the different sampling strategies to collect intestinal microbiota (feces, biopsies, swabs, brushes, and washing aspirates). In particular, this article recapitulates the current knowledge on MAM in colorectal adenomas and serrated polyps, since studying the intestinal microbiota associated with early-stage tumors can elucidate the molecular mechanisms underpinning CRC carcinogenesis.

Streptococcus bovis infection of the central nervous system in adults: Report of 4 cases and literature review

OBJECTIVES

To describe the clinical features, history and association with intestinal disease in central nervous system (CNS) S. bovis infections.

METHODS

Four cases of S. bovis CNS infections from our institution are presented. Additionally a systematic literature review of articles published between 1975 and 2021 in PubMed/MEDLINE was conducted.

RESULTS

52 studies with 65 cases were found; five were excluded because of incomplete data. In total 64 cases were analyzed including our four cases: 55 with meningitis and 9 with intracranial focal infections. Both infections were frequently associated with underlying conditions (70.3%) such as immunosuppression (32.8%) or cancer (10.9%). In 23 cases a biotype was identified, with biotype II being the most frequent (69.6%) and S. pasteurianus the most common within this subgroup. Intestinal diseases were found in 60.9% of cases, most commonly neoplasms (41.0%) and Strongyloides infestation (30.8%). Overall mortality was 17.1%, with a higher rate in focal infection (44.4% vs 12.7%; p=0.001).

CONCLUSIONS

CNS infections due to S. bovis are infrequent and the most common clinical form is meningitis. Compared with focal infections, meningitis had a more acute course, was less associated with endocarditis and had a lower mortality. Immunosuppression and intestinal disease were frequent in both infections.

Association of the Streptococcus bovis/Streptococcus equinus Complex With Colorectal Neoplasia: A Systematic Review and Meta-analysis

Background

Invasive infection with Streptococcus bovis/Streptococcus equinus complex (SBSEC) bacteria is associated with underlying colorectal neoplasia. However, the link between intestinal or fecal colonization with SBSEC isolates or antibody responses to SBSEC members and colorectal cancer is not thoroughly investigated in the literature.

Methods

We searched the PubMed, EMBASE, and Web of Science databases for case-control studies as well as retrospective or prospective cohort studies reporting an association between SBSEC bacteria and colorectal neoplasia.

Results

We identified 22 studies (15 case-control and 7 cohort) that met our inclusion criteria. Among the cohort studies, patients with SBSEC bacteremia were 3.73 times more likely to have underlying colorectal cancer compared with individuals with no bacteremia (relative risk [RR], 3.73; 95% CI, 2.79-5.01), whereas the risk of underlying colorectal adenoma in patients with SBSEC bacteremia was not significantly increased (RR, 5.00; 95% CI, 0.83-30.03). In case-control studies, patients with colorectal cancer were 2.27 times more likely to have evidence of intestinal or fecal colonization with SBSEC isolates (odds ratio [OR], 2.27; 95% CI, 1.11-4.62) and immunoglobulin G (IgG) antibody responses to SBSEC antigens (OR, 2.27; 95% CI, 1.06-4.86) compared with controls. Patients with colorectal adenoma were not more likely to be colonized with SBSEC isolates compared with controls (OR, 1.12; 95% CI, 0.55-2.25).

Conclusions

Apart from the well-established association of SBSEC bacteremia and underlying colorectal cancer, intestinal or fecal colonization with SBSEC isolates and IgG antibody responses to SBSEC antigens were higher in patients with colorectal cancer compared with controls. Neither bacteremia from SBSEC isolates nor colonization with SBSEC bacteria was associated with underlying colorectal adenoma.

Global proteomic identifies multiple cancer-related signaling pathways altered by a gut pathobiont associated with colorectal cancer

In this work, we investigated the oncogenic role of Streptococcus gallolyticus subsp. gallolyticus (SGG), a gut bacterium associated with colorectal cancer (CRC). We showed that SGG UCN34 accelerates colon tumor development in a chemically induced CRC murine model. Full proteome and phosphoproteome analysis of murine colons chronically colonized by SGG UCN34 revealed that 164 proteins and 725 phosphorylation sites were differentially regulated. Ingenuity Pathway Analysis (IPA) indicates a pro-tumoral shift specifically induced by SGG UCN34, as ~ 90% of proteins and phosphoproteins identified were associated with digestive cancer. Comprehensive analysis of the altered phosphoproteins using ROMA software revealed up-regulation of several cancer hallmark pathways such as MAPK, mTOR and integrin/ILK/actin, affecting epithelial and stromal colonic cells. Importantly, an independent analysis of protein arrays of human colon tumors colonized with SGG showed up-regulation of PI3K/Akt/mTOR and MAPK pathways, providing clinical relevance to our findings. To test SGG's capacity to induce pre-cancerous transformation of the murine colonic epithelium, we grew ex vivo organoids which revealed unusual structures with compact morphology. Taken together, our results demonstrate the oncogenic role of SGG UCN34 in a murine model of CRC associated with activation of multiple cancer-related signaling pathways.

Discovery of potent natural product higenamine derivatives as novel Anti-Fusobacterium nucleatum agents

Fusobacterium nucleatum (F. nucleatum) is closely associated with the occurrence and development of colorectal cancer (CRC). Discovery of specific antibacterial agents against F. nucleatum was urgent for the prevention and treatment of CRC. We screened a natural product library and successfully identified higenamine as an antibacterial hit against F. nucleatum. Further hit optimizations led to the discovery of new higenamine derivatives with improved anti-F. nucleatum activity. Among them, compound 7c showed potent antibacterial activity against F. nucleatum (MIC50 = 0.005 μM) with good selectivity toward intestinal bacteria and normal cells. It significantly inhibited the migration of CRC cells induced by F. nucleatum. Mechanism study revealed that compound 7c impaired the integrity of biofilm and cell wall, which represents a good starting point for the development of novel anti-F. nucleatum agents.

Characterization of TelE, a T7SS LXG Effector Exhibiting a Conserved C-Terminal Glycine Zipper Motif Required for Toxicity

Streptococcus gallolyticus subsp. gallolyticus (SGG) is an opportunistic bacterial pathogen strongly associated with colorectal cancer. Here, through comparative genomics analysis, we demonstrated that the genetic locus encoding the type VIIb secretion system (T7SSb) machinery is uniquely present in SGG in two different arrangements. SGG UCN34 carrying the most prevalent T7SSb genetic arrangement was chosen as the reference strain. To identify the effectors secreted by this secretion system, we inactivated the essC gene encoding the motor of this machinery. A comparison of the proteins secreted by UCN34 wild type and its isogenic ΔessC mutant revealed six T7SSb effector proteins, including the expected WXG effector EsxA and three LXG-containing proteins. In this work, we characterized an LXG-family toxin named herein TelE promoting the loss of membrane integrity. Seven homologs of TelE harboring a conserved glycine zipper motif at the C terminus were identified in different SGG isolates. Scanning mutagenesis of this motif showed that the glycine residue at position 470 was crucial for TelE membrane destabilization activity. TelE activity was antagonized by a small protein TipE belonging to the DUF5085 family. Overall, we report herein a unique SGG T7SSb effector exhibiting a toxic activity against nonimmune bacteria. IMPORTANCE In this study, 38 clinical isolates of Streptococcus gallolyticus subsp. gallolyticus (SGG) were sequenced and a genetic locus encoding the type VIIb secretion system (T7SSb) was found conserved and absent from 16 genomes of the closely related S. gallolyticus subsp. pasteurianus (SGP). The T7SSb is a bona fide pathogenicity island. Here, we report that the model organism SGG strain UCN34 secretes six T7SSb effectors. One of the six effectors named TelE displayed a strong toxicity when overexpressed in Escherichia coli. Our results indicate that TelE is probably a pore-forming toxin whose activity can be antagonized by a specific immunity protein named TipE. Overall, we report a unique toxin-immunity protein pair and our data expand the range of effectors secreted through T7SSb.

Role of gut microbiota and bacterial metabolites in mucins of colorectal cancer

Colorectal cancer (CRC) is a major health burden, accounting for approximately 10% of all new cancer cases worldwide. Accumulating evidence suggests that the crosstalk between the host mucins and gut microbiota is associated with the occurrence and development of CRC. Mucins secreted by goblet cells not only protect the intestinal epithelium from microorganisms and invading pathogens but also provide a habitat for commensal bacteria. Conversely, gut dysbiosis results in the dysfunction of mucins, allowing other commensals and their metabolites to pass through the intestinal epithelium, potentially triggering host responses and the subsequent progression of CRC. In this review, we summarize how gut microbiota and bacterial metabolites regulate the function and expression of mucin in CRC and novel treatment strategies for CRC.

The interaction between liver cirrhosis, infection by Streptococcus bovis, and colon cancer

Whether cirrhotic patients with Streptococcus bovis bacteremia have an increased risk of colorectal neoplasm is uncertain. A multicentric retrospective cohort study was conducted investigating associations between S. bovis biotype and species, cirrhosis, and colorectal neoplasm. Out of 779 patients with S. bovis bacteremia, 69 (8.7%) had cirrhosis. No differences were found in the prevalence of colorectal neoplasm between cirrhotic and non-cirrhotic patients undergoing colonoscopy. Among cirrhotic patients, prevalence of colorectal neoplasms was higher in S. bovis biotype I (S. gallolyticus) bacteremia (80%) than in S. bovis biotype II (33.3%; p < 0.007). In conclusion, risk of colorectal neoplasm is high among cirrhotic patients with S. gallolyticus bacteremia.

Species and biotypes of Streptococcus bovis causing infective endocarditis

INTRODUCTION

Streptococcus bovis/equinus complex (SBEC) is a major cause of infective endocarditis (IE), although its incidence varies greatly depending on the geographical area. The characteristics of IE caused by Streptococcus gallolyticus susp. gallolyticus are well known; there are hardly any descriptions of IE caused by other species or biotypes.

METHODS

Retrospective cohort study, from 1990 to 2019, of all SBEC IE in adults in three Spanish hospitals, Lugo (LH), Barcelona (BH) and Ferrol (FH) where the population is mainly rural, urban and mixed, respectively. The incidence of IE was analyzed in 3 areas. Clinical characteristics of IE (277 cases, 258 biotyped) were compared according to SBEC species and biotypes.

RESULTS

There are significant differences between the incidence of SBEC IE in HL (27.9/10⁶) vs. HF and HB (8.8 and 7,1, respectively, p<0.001). We found significant differences (SbI vs. SbII) in mean age (68.5 vs. 73 years; p<0.01), duration of symptoms before diagnosis (46.9±46.5 vs. 30.4±40.9 days; p<0.01), presence of comorbidities: 39.1% (78) vs. 54.2% (32; p<0.04), predisposing heart illness:62.3% (124) vs. 81.3% (48; p<0.006), particularly, prosthetic or intravascular devices IE: 24.6% (49) vs. 52.4% (31; p<0.001), bi-valve involvement:23.6% (47) vs. 11.8% (7; p<0.05) and heart failure: 24.6% (49) vs. 38.9% (23; p<0.03). There were no significant differences in embolic events, need for surgery or mortality. The association with CRC was high in both groups: 77.7% vs. 66.6%.

CONCLUSIONS

IE due to SBEC has geographical variations in incidence and different clinical characteristics among biotypes. The association with CRC was high.

Streptococcus gallolyticus subspecies pasteurianus bacteremia accompanied by acute pancreatitis

INTRODUCTION

While Streptococcus gallolyticus subsp. gallolyticus has a well-known association with colorectal cancer, an epidemiological association between S. gallolyticus subsp. pasteurianus (SGSP) and hepatobiliary diseases has been suggested. Here we described a case of gallstone pancreatitis and SGSP bacteremia in which species-identification by Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) helped to diagnose the biliary etiology.

CASE REPORT

A 61-year-old Japanese man without history of alcohol consumption was hospitalized for acute pancreatitis. His past medical history included endoscopically treated familial adenomatous polyposis. A blood culture grew gram-positive cocci, identified to be SGSP by MALDI-TOF MS. A contrast-enhanced computed tomography scan showed pancreatic enlargement and increased fatty tissue concentration around the perirenal and pararenal space. He was diagnosed with acute pancreatitis and subsequently recovered after appropriate antimicrobial therapy and supportive care. Subsequent magnetic resonance cholangiopancreatography showed gallstones in the gallbladder neck, suggesting the cause of the acute pancreatitis. Seven months after admission, cholecystectomy was performed for cholelithiasis.

CONCLUSION

This case highlights that the identification of subspecies enabled by MALDI-TOF MS supports the diagnosis of the underlying etiology from the microbiological point of view.

Bacteraemia and infective endocarditis with Streptococcus bovis-Streptococcus equinus-complex: a retrospective cohort study

BACKGROUND

Streptococcus bovis/equinus complex (SBSEC) comprise several species and subspecies and is a common cause of infective endocarditis (IE). S. gallolyticus subsp. gallolyticus (Sg gallolyticus) accounts for a majority of SBSEC IE, but the risk of IE for other subspecies is largely unknown. We aimed to investigate the clinical presentation of bacteraemia, and proportion of patients with IE in bacteraemia with the most common subspecies.

METHODS

A retrospective cohort study of SBSEC-bacteraemia identified in clinical laboratory databases, in Skåne Region, Sweden, 2003-2018. Bacteraemia with Sg gallolyticus, S. gallolyticus subsp. pasteurianus (Sg pasteurianus), S. lutetiensis and S. infantarius subsp. infantarius (Si infantarius) were included. Subspecies was identified by whole genome sequencing. Medical charts were reviewed according to a predetermined protocol, IE was defined by the criteria from European Society of Cardiology.

RESULTS

In total, 210 episodes of SBSEC-bacteraemia were included. Definite IE was identified in 28/210 (13%) episodes. Of these, 7/28 (25%) were prosthetic valve-IE, 1/28 (4%) related to a cardiovascular implantable electronic device and 10/28 (36%) required heart valve surgery. The proportions of IE among different subspecies were: Sg gallolyticus 17/52 (33%), Si infantarius 5/31 (16%), Sg pasteurianus 4/83 (5%) and S. lutetiensis 2/44 (5%) (p < 0.001). Sg pasteurianus and S. lutetiensis were more often associated with intra-abdominal- and polymicrobial infection.

CONCLUSION

The proportion of IE in SBSEC-bacteraemia varies substantially depending on subspecies. Echocardiography should always be considered in bacteraemia with Sg gallolyticus and Si infantarius, and can sometimes be omitted in bacteraemia with Sg pasteurianus and S. lutetiensis.

Gut microbiota modulation: a tool for the management of colorectal cancer

Colorectal cancer (CRC) is the second cause of cancer death and the third most frequently diagnosed cancer. Besides the lifestyle, genetic and epigenetic alterations, and environmental factors, gut microbiota also plays a vital role in CRC development. The interruption of the commensal relationship between gut microbiota and the host could lead to an imbalance in the bacteria population, in which the pathogenic bacteria become the predominant population in the gut. Different therapeutic strategies have been developed to modify the gut immune system, prevent pathogen colonization, and alter the activity and composition of gut microbiota, such as prebiotics, probiotics, postbiotics, antibiotics, and fecal microbiota transplantation (FMT). Even though the employed strategies exhibit promising results, their translation into the clinic requires evaluating potential implications and risks, as well as assessment of their long-term effects. This study was set to review the gut microbiota imbalances and their relationship with CRC and their effects on CRC therapy, including chemotherapy and immunotherapy. More importantly, we reviewed the strategies that have been used to modulate gut microbiota, their impact on the treatment of CRC, and the challenges of each strategy.

Relationship among Streptococcus gallolyticus Subsp. gallolyticus, Enterococcus faecalis and Colorectal Neoplasms in Recurrent Endocarditis: A Historical Case Series

Objectives: The role of colorectal neoplasms (CRN) as a common potential source of recurrent Streptococcus gallolyticus subsp. gallolyticus (SGG) and Enterococcus faecalis (EF) endocarditis remains unstudied. We aimed to investigate what proportion of episodes of recurrent endocarditis are caused by a succession of SGG and EF, or vice versa, and to assess the role of a colonic source in such recurrent episodes. Methods: we conducted a retrospective analysis of two prospective endocarditis cohorts (1979–2019) from two Spanish hospitals, providing descriptive analyses of the major features of the endocarditis episodes, colonoscopy findings, and histologic results. Results: among 1552 IE episodes, 204 (13.1%) were caused by EF and 197 (12.7%) by SGG, respectively. There were 155 episodes (10%) of recurrent IE, 20 of which (12.9%) were due to a succession of SGG/EF IE in 10 patients (the first episode caused by SGG in eight cases, and by EF in two cases). The median follow-up was 86 (interquartile range 34–156) months. In 8/10 initial episodes, the causative microorganism was SGG, and all patients were diagnosed with CRN either during the initial episode or during follow-up. During the second episode of IE or follow-up, colonoscopies revealed CRN in six patients. Conclusions: There seems to be an association between SGG and EF in recurrent endocarditis that warrants further investigation. Our findings reinforce the need for systematically performing colonoscopy in the event of endocarditis caused by both microorganisms.

Bacteremia with Anaerobic Bacteria and Association with Colorectal Cancer: A Population-based Cohort Study

BACKGROUND

There is a well-described association between bacteremia with bovis group streptococci or Clostridium septicum and an increased risk of a colorectal cancer (CRC) diagnosis. We wanted to investigate the possible existence of a similar association between CRC and bacteremia with other bacteria belonging to the gut microbiota.

METHODS

A population based cohort study in a population about 2 million people including 45,774 bacteremia episodes and 231,387 blood culture negative cases was performed in the Region of Southern Denmark and Region Zealand (Denmark) from 2007-2016. Episodes of bacteremia were combined with the Danish central register for CRC. We performed Cox's regression analysis with hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

The study results confirmed previous findings of an increased risk of a CRC diagnosis after bacteremia with the bovis group streptococci (risk within a year: 4.3%; HR [95% CI]: 8.46 [3.51-20.4]) or C. septicum (20.8%; 76.2 [42.0-138]). Furthermore, Bacteroides ovatus (6.7%; 20.3 [5.04-81.8]), Bacteroides uniformis (5.4%; 16.2 [4.02-65.7]), Clostridium tertium (3.6 %; 13.9 [1.96-99.4]), Fusobacterium spp. (excluding F. necrophorum) (3.0 %; 8.51 [2.73-26.5]), and Gram-positive anaerobic cocci (3.6 %; 10.9 [4.50-26.3]) were also associated with an increased risk of a CRC diagnosis compared to patients with negative blood cultures (0.4%).

CONCLUSIONS

Bacteremia with several specific gut microbiota anaerobic bacteria is associated with a high risk of a diagnosis of CRC, indicating the need for colorectal workup in such cases. Importantly, this strategy also holds the possible additional benefit of detecting adenomas or other premalignant conditions, which were not included in the present study.

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

Background

Mucosal infiltration by certain bacterial species may contribute to the development and progression of colorectal cancer (CRC). There is considerable variation in reported detection rates in human CRC samples and the extent to which bacterial infiltration varies across regions of the primary tumour is unknown. This study aimed to determine if there is an optimal site for bacterial detection within CRC tumours.

Methods

Presence of target bacterial species was assessed by quantitative real-time PCR (qPCR) in 42 human CRC tumours. Abundance in primary tumour regions, normal epithelium and at metastatic sites was investigated in an expanded cohort of 51 patients. Species presence/absence was confirmed by diversity profiling in five patients. Correlation with total bacterial load and clinicopathological features was assessed.

Results

Fusobacterium nucleatum and Bacteroides fragilis were detected in tumours from 43% and 24% of patients, respectively (17% positive for both species). The optimal detection site was the tumour luminal surface (TLS). Patients testing positive at the TLS frequently tested negative at other sites, including central tumour and invasive margin. F. nucleatum was detected at a higher frequency in tumour versus normal epithelium (p < 0.01) and was associated with more advanced disease (p = 0.01). Detection of both species correlated with total bacterial load. However, corroboration of qPCR results via diversity profiling suggests detection of these species may indicate a specific microbial signature.

Conclusions

This study supports a role for F. nucleatum in CRC development. Presence of F. nucleatum and B. fragilis varies across primary tumour regions, with the TLS representing the optimal site for bacterial detection.

Streptococcus bovis-bacteremia: subspecies distribution and association with colorectal cancer: a retrospective cohort study

This study aimed to describe the incidence of Streptococcus bovis/Streptococcus equinus complex (SBSEC) bacteremia, distribution of the SBSEC subspecies, and their respective association with colorectal cancer (CRC). A population-based retrospective cohort study of all episodes of SBSEC-bacteremia from 2003 to 2018 in Skåne Region, Sweden. Subspecies was determined by whole-genome sequencing. Medical charts were reviewed. The association between subspecies and CRC were analysed using logistic regression. In total 266 episodes of SBSEC-bacteremia were identified and the average annual incidence was 2.0 per 100 000 inhabitants. Of the 236 isolates available for typing, the most common subspecies was S. gallolyticus subsp. pasteurianus 88/236 (37%) followed by S. gallolyticus subsp. gallolyticus 58/236 (25%). In order to determine the risk of cancer following bacteremia, an incidence cohort of 174 episodes without a prior diagnosis of CRC or metastasised cancer was followed for 560 person-years. CRC was found in 13/174 (7%), of which 9 (69%) had S. gallolyticus subsp. gallolyticus-bacteremia. In contrast to other European studies, S. gallolyticus subsp. pasteurianus was the most common cause of SBSEC-bacteremia. CRC diagnosis after bacteremia was strongly associated with S. gallolyticus subsp. gallolyticus-bacteremia. Identification of SBSEC subspecies can guide clinical decision-making regarding CRC work-up following bacteremia.

Enterococcus faecalis endocarditis: what's next?

Enterococcus faecalis infective endocarditis (EFIE) is a complex entity in rapid evolution. Although largely relevant findings from recent studies have advanced the knowledge on EFIE and led to some changes in clinical guidelines, there are still a number of gaps to be filled. Coordinated, international, multicenter efforts are needed to obtain quality data that rend the health systems and scientific community prepared enough to understand and handle this infection. In this Perspective, some of the most relevant aspects concerning the epidemiology, clinical presentation and outcomes, diagnostic approaches and antibiotic therapy of EFIE are addressed. Also, several potential future clinical developments in the field are discussed.

Effects of infections on the pathogenesis of cancer

Several studies have shown an inverse relationship between acute infections and cancer development. On the other hand, there is a growing evidence that chronic infections may contribute significantly to the carcinogenesis. Factors responsible for increased susceptibility to infections may include modifications of normal defence mechanisms or impairment of host immunity due to altered immune function, genetic polymorphisms, ageing and malnourishment. Studies have demonstrated that children exposed to febrile infectious diseases show a subsequent reduced risk for ovarian cancer, melanoma and many other cancers, while common acute infections in adults are associated with reduced risks for melanoma, glioma, meningioma and multiple cancers. Chronic inflammation associated with certain infectious diseases has been suggested as a cause for the development of tumours. Mechanisms of carcinogenesis due to infections include cell proliferation and DNA replication by mitogen-activated protein kinase pathway, production of toxins that affect the cell cycle and lead to abnormal cell growth and inhibition of apoptosis. This review was aimed to summarize the available evidence on acute infections as a means of cancer prevention and on the role of chronic infections in the development and progression of cancer.

A type VII secretion system of Streptococcus gallolyticus subsp. gallolyticus contributes to gut colonization and the development of colon tumors

Streptococcus gallolyticus subspecies gallolyticus (Sgg) has a strong clinical association with colorectal cancer (CRC) and actively promotes the development of colon tumors. However, the molecular determinants involved in Sgg pathogenicity in the gut are unknown. Bacterial type VII secretion systems (T7SS) mediate pathogen interactions with their host and are important for virulence in pathogenic mycobacteria and Staphylococcus aureus. Through genome analysis, we identified a locus in Sgg strain TX20005 that encodes a putative type VII secretion system (designated as SggT7SS^T05). We showed that core genes within the SggT7SS^T05 locus are expressed in vitro and in the colon of mice. Western blot analysis showed that SggEsxA, a protein predicted to be a T7SS secretion substrate, is detected in the bacterial culture supernatant, indicating that this SggT7SS^T05 is functional. Deletion of SggT7SS^T05 (TX20005Δesx) resulted in impaired bacterial adherence to HT29 cells and abolished the ability of Sgg to stimulate HT29 cell proliferation. Analysis of bacterial culture supernatants suggest that SggT7SS^T05-secreted factors are responsible for the pro-proliferative activity of Sgg, whereas Sgg adherence to host cells requires both SggT7SS^T05-secreted and bacterial surface-associated factors. In a murine gut colonization model, TX20005Δesx showed significantly reduced colonization compared to the parent strain. Furthermore, in a mouse model of CRC, mice exposed to TX20005 had a significantly higher tumor burden compared to saline-treated mice, whereas those exposed to TX20005Δesx did not. Examination of the Sgg load in the colon in the CRC model suggests that SggT7SS^T05-mediated activities are directly involved in the promotion of colon tumors. Taken together, these results reveal SggT7SS^T05 as a previously unrecognized pathogenicity determinant for Sgg colonization of the colon and promotion of colon tumors.

Colorectal cancer (CRC) is a leading cause of cancer-related death. The development of CRC can be strongly influenced by specific gut microbes. Understanding how gut microbes modulate CRC is critical to developing novel strategies to improve clinical diagnosis and treatment of this disease. S. gallolyticus subsp. gallolyticus (Sgg) has a strong clinical association with CRC and actively promotes the development of colon tumors. However, the specific Sgg molecules that mediate its pro-tumor activity are unknown. Here we report the first characterization of a type VII secretion system (T7SS) in Sgg, designated as SggT7SS^T05. We further demonstrate that SggT7SS^T05-mediated activities are important for Sgg to colonize the colon and to promote the development of colon tumors. These findings reveal SggT7SS^T05 as a novel pathogenicity determinant of Sgg and provide a critical breakthrough in our efforts to understand how Sgg influences the development of CRC. Future investigations of the biological activities of specific effectors of SggT7SS^T05 will likely lead to the discovery of Sgg molecules that can be used as diagnostic markers and intervention targets aimed at mitigating the harmful effect of Sgg.

Characterization of a Four-Component Regulatory System Controlling Bacteriocin Production in Streptococcus gallolyticus

Bacteriocins are natural antimicrobial peptides produced by bacteria to kill closely related competitors. The opportunistic pathogen Streptococcus gallolyticus subsp. gallolyticus was recently shown to outcompete commensal enterococci of the murine microbiota under tumoral conditions thanks to the production of a two-peptide bacteriocin named gallocin. Here, we identified four genes involved in the regulatory control of gallocin in S. gallolyticus subsp. gallolyticus UCN34 that encode a histidine kinase/response regulator two-component system (BlpH/BlpR), a secreted peptide (GSP [gallocin-stimulating peptide]), and a putative regulator of unknown function (BlpS). While BlpR is a typical 243-amino-acid (aa) response regulator possessing a phospho-receiver domain and a LytTR DNA-binding domain, BlpS is a 108-aa protein containing only a LytTR domain. Our results showed that the secreted peptide GSP activates the dedicated two-component system BlpH/BlpR to induce gallocin transcription. A genome-wide transcriptome analysis indicates that this regulatory system (GSP-BlpH/BlpR) is specific for bacteriocin production. Importantly, as opposed to BlpR, BlpS was shown to repress gallocin gene transcription. A conserved operator DNA sequence of 30 bp was found in all promoter regions regulated by BlpR and BlpS. Electrophoretic mobility shift assays (EMSA) and footprint assays showed direct and specific binding of BlpS and BlpR to various regulated promoter regions in a dose-dependent manner on this conserved sequence. Gallocin expression appears to be tightly controlled in S. gallolyticus subsp. gallolyticus by quorum sensing and antagonistic activity of 2 LytTR-containing proteins. Competition experiments in gut microbiota medium and 5% CO₂ to mimic intestinal conditions demonstrate that gallocin is functional under these in vivo-like conditions.IMPORTANCE Streptococcus gallolyticus subsp. gallolyticus, formerly known as Streptococcus bovis biotype I, is an opportunistic pathogen causing septicemia and endocarditis in the elderly often associated with asymptomatic colonic neoplasia. Recent studies indicate that S. gallolyticus subsp. gallolyticus is both a driver and a passenger of colorectal cancer. We previously showed that S. gallolyticus subsp. gallolyticus produces a bacteriocin, termed gallocin, enabling colonization of the colon under tumoral conditions by outcompeting commensal members of the murine microbiota such as Enterococcus faecalis Here, we identified and extensively characterized a four-component system that regulates gallocin production. Gallocin gene transcription is activated by a secreted peptide pheromone (GSP) and a two-component signal transduction system composed of a transmembrane histidine kinase receptor (BlpH) and a cytosolic response regulator (BlpR). Finally, a DNA-binding protein (BlpS) was found to repress gallocin genes transcription, likely by antagonizing BlpR. Understanding gallocin regulation is crucial to prevent S. gallolyticus subsp. gallolyticus colon colonization under tumoral conditions.

Prevalence of Colorectal Neoplasms Among Patients With Enterococcus faecalis Endocarditis in the GAMES Cohort (2008-2017)

OBJECTIVE

To investigate the rate of colorectal neoplasms (CRNs) in patients who have Enterococcus faecalis infective endocarditis (EFIE) with available colonoscopies and to assess whether this is associated with the identification of a focus the infection.

PATIENTS AND METHODS

Retrospective analysis of data from a prospective multicenter study involving 35 centers who are members of the Grupo de Apoyo para el Manejo de la Endocarditis en España [Support Group for the Management of Infective Endocarditis in Spain] cohort. A specific set of queries regarding information on colonoscopy and histopathology of colorectal diseases was sent to each participating center. Four-hundred sixty-seven patients with EFIE were included from January 1, 2008, to December 31, 2017, from whom data on colonoscopy performance and results were available in 411 patients.

RESULTS

One hundred forty-two (34.5%) patients had a colonoscopy close to the EFIE episode. The overall rate of colorectal diseases was 70.4% (100 of 142), whereas the prevalence of CRN (advanced adenomas and colorectal carcinoma) was 14.8% (21 of 142), with no significant differences between the group of EFIE of unknown focus and that with an identified focus.

CONCLUSION

Our study adds to prior evidence suggesting a much higher rate of CRN among patients with EFIE than in the general population of the same age and sex. In addition, our findings suggest that this phenomenon might take place both in EFIE with an unknown and an identified source of infection.

Gut Microbiota and Colorectal Cancer Development: A Closer Look to the Adenoma-Carcinoma Sequence

There is wide evidence that CRC could be prevented by regular physical activity, keeping a healthy body weight, and following a healthy and balanced diet. Many sporadic CRCs develop via the traditional adenoma-carcinoma pathway, starting as premalignant lesions represented by conventional, tubular or tubulovillous adenomas. The gut bacteria play a crucial role in regulating the host metabolism and also contribute to preserve intestinal barrier function and an effective immune response against pathogen colonization. The microbiota composition is different among people, and is conditioned by many environmental factors, such as diet, chemical exposure, and the use of antibiotic or other medication. The gut microbiota could be directly involved in the development of colorectal adenomas and the subsequent progression to CRC. Specific gut bacteria, such as Fusobacterium nucleatum, Escherichia coli, and enterotoxigenic Bacteroides fragilis, could be involved in colorectal carcinogenesis. Potential mechanisms of CRC progression may include DNA damage, promotion of chronic inflammation, and release of bioactive carcinogenic metabolites. The aim of this review was to summarize the current knowledge on the role of the gut microbiota in the development of CRC, and discuss major mechanisms of microbiota-related progression of the adenoma-carcinoma sequence.

Helicobacter pylori Infection and the Development of Advanced Colorectal Neoplasia

BACKGROUND

An association between Helicobacter pylori infection and colorectal neoplasia has been reported in cross-sectional studies.

GOALS

We examined the association between H. pylori infection and the development of advanced colorectal neoplasia (AN) in a screening cohort.

STUDY

We identified 3753 adults, who underwent screening and subsequent surveillance colonoscopies. The primary outcome was the development of metachronous AN, as confirmed by surveillance colonoscopy. H. pylori infection status was assessed by an H. pylori-specific immunoglobulin G antibody test. Sensitivity analysis was also performed by H. pylori infection status on the basis of histology.

RESULTS

During a median follow-up of 41 months, the incidence of AN was 3.2% and 1.7% in participants with and without H. pylori infection, respectively. In multivariable analysis adjusted for age, body mass index, smoking status, alcohol intake, family history of colorectal cancer, and baseline adenoma characteristics, the hazard ratio [95% confidence interval (CI)] for metachronous AN was 1.74 (1.11-2.73) in participants with H. pylori seropositivity, compared with those without H. pylori seropositivity. The association was consistent with H. pylori infection status on the basis of histology (adjusted hazard ratio, 3.51; 95% CI, 1.64-7.51). In the subgroup analysis, the positive association was observed in both no-adenoma and adenoma removal subgroups.

CONCLUSIONS

In a cohort study, H. pylori infection was associated with an increased risk of AN development. This association was consistent in both the serological and histologic assessment of H. pylori infection. Prospective studies are necessary to determine whether H. pylori eradication can reduce the risk of colorectal neoplasia.

Infectious disease consultations and newly diagnosed cancer patients: A single-center retrospective observational study

Noninfectious diseases may be diagnosed during infectious disease (ID) consultations. Among non-IDs, cancer diagnosis is important; however, epidemiological data describing the relationship between ID consultations and newly diagnosed cancer patients are scarce. This study described the frequency and tendency of new cancer diagnoses in patients after ID consultation.This retrospective study included adult inpatients who underwent ID consultations between October 2016 and March 2018. The demographic data and clinical manifestations of each case are described.Among the 380 inpatients who underwent ID consultations, 6 (1.6%) received a new cancer diagnosis after ID consultation. Among the initial most likely diagnoses, 3 patients were diagnosed with IDs and 3 were diagnosed with non-IDs. The initial most likely ID diagnosis was important for new cancer diagnoses (P = .004, odds ratio: 11.1, 95% confidence interval: 2.11-57.2); diagnostic errors, as judged by the physicians, occurred in 2 of the 6 cases.While the frequency of establishing new diagnoses during ID consultations is low, coexisting infection and cancer is possible. ID specialists should identify any patterns related to new cancer diagnosis in patients to prevent diagnostic error and improve the quality of diagnosis.

How to manage patients in whom malignancy and infective endocarditis are associated: a review

Objective. Infective endocarditis (IE) is a potentially short-term lethal condition. An association with malignancy could complicate diagnostic and therapeutic decisions. The questions to be answered are: (1) which type of malignancies are encountered; (2) how often has the association between malignancy and IE been described, and (3) what are thus far the diagnostic and treatment strategies for patients with both conditions. Methods. A literature search from 2010 to 2018 has been performed with the focus on IE and cancer/malignancy/neoplasm, as well as with risk factors for adverse outcome, when cancer was included in the analysis. Results. An association between digestive, respiratory and hematologic malignancy with IE has been observed in four large databases. The most important mechanisms for this association are a "port of entry" and immune suppression. Sixteen studies dealt with the effect of short and mid-term cancer on the outcome of surgery of IE in these patients. No uniform management strategy could be identified. It seems that a malignancy does not alter the short-term outcome for IE, although referral to a tertiary cardiac center and surgical treatment are less common for patients with known malignancy. Conclusions. Although there is an association between malignancy and IE, no treatment strategy has yet been developed for these patients. Short-term outcome of IE is unaltered by cancer. In most papers, the effect of cancer on mid-term survival is only significant in a univariate analysis, without being a predictor. The results indicate that cardiac surgery for IE should not be withheld in patients in whom a treatable malignancy has been found.

Risk factors for the carriage of Streptococcus infantarius subspecies infantarius isolated from African fermented dairy products

Streptococcus infantarius subsp. infantarius (Sii) has been identified as predominant lactic acid bacteria in spontaneously fermented dairy products (FDPs) in sub-Saharan Africa including Côte d'Ivoire. However, Sii belongs to the Streptococcus bovis/Streptococcus equinus complex (SBSEC). Most SBSEC members are assumed to be involved as opportunistic pathogens in serious diseases in both humans and animals. A population-based cross-sectional survey, including 385 participants was conducted in Korhogo, northern Côte d'Ivoire, to identify risk factors for Sii fecal carriage, including consumption of local FDPs. A structured questionnaire was used to gather participant's socio-demographic and economic characteristics, their relation to livestock and dietary habits. In addition, fresh stool and milk samples were collected. The identification of Sii was done using a SBSEC-specific PCR assay targeting 16S rRNA and groEL genes. The overall prevalence of SBSEC and Sii carriage was 23.2% (confidence interval CI 95% = 18.9-27.5) and 12.0% (CI 95% = 8.4-15.5) for stool, respectively. Prevalence of Sii was significantly higher in consumers of artisanal butter compared with non-consumers (57.1% vs 10.1%, odds ratio OR: 11.9, 95% CI: 3.9-36.6), as well as in persons handling livestock (OR = 3.9; 95% CI = 1.6-9.3) and livestock primary products (OR = 5.7; 95% CI = 2.3-14.3). The closer contact with livestock was a risk factor for Sii fecal carriage. Sii strains were isolated from fresh and fermented milk products with a prevalence of 30.4% and 45.4%, respectively. Analysis of Sii population structure through the SBSEC multi locus sequence typing assay revealed a close relationship across human and dairy isolates, possibly linked to a Kenyan human isolate. All these outcomes underline the interest of in-depth investigations on the ecology, potential reservoirs and pathways of contamination by Sii at the human-animal-environment interface in comparison to yet to be collected data from Europe, Asia and the Americas to further elucidate the various roles of Sii.

Gut microbiota in colorectal cancer: mechanisms of action and clinical applications

Colorectal cancer (CRC) accounts for about 10% of all new cancer cases globally. Located at close proximity to the colorectal epithelium, the gut microbiota comprises a large population of microorganisms that interact with host cells to regulate many physiological processes, such as energy harvest, metabolism and immune response. Sequencing studies have revealed microbial compositional and ecological changes in patients with CRC, whereas functional studies in animal models have pinpointed the roles of several bacteria in colorectal carcinogenesis, including Fusobacterium nucleatum and certain strains of Escherichia coli and Bacteroides fragilis. These findings give new opportunities to take advantage of our knowledge on the gut microbiota for clinical applications, such as gut microbiota analysis as screening, prognostic or predictive biomarkers, or modulating microorganisms to prevent cancer, augment therapies and reduce adverse effects of treatment. This Review aims to provide an overview and discussion of the gut microbiota in colorectal neoplasia, including relevant mechanisms in microbiota-related carcinogenesis, the potential of utilizing the microbiota as CRC biomarkers, and the prospect for modulating the microbiota for CRC prevention or treatment. These scientific findings will pave the way to clinically translate the use of gut microbiota for CRC in the near future.

Intestinal microbiota and colorectal cancer: changes in the intestinal microenvironment and their relation to the disease

Tools that predict the risk of colorectal cancer are important for early diagnosis, given the high mortality rate for this cancer. The composition of the intestinal microbiota is now considered to be a risk factor for the development of colorectal cancer. This discovery has motivated a growing number of studies to identify the micro-organisms responsible for the onset and/or progression of colorectal cancer. With this in mind, this review discusses the relationship between the composition of the intestinal microbiota and colorectal cancer risk. Prospective and case-control studies indicate that the intestinal microbiota of individuals with colorectal cancer usually contains a greater proportion of bacteria responsible for gastrointestinal tract inflammatory diseases, as well as bacteria that produce toxins and carcinogenic metabolites. In contrast, there tends to be a reduced presence of butyric acid-producing bacteria, probiotic bacteria and potentially probiotic bacteria. Despite these differences, the onset and development of colorectal cancer cannot be attributed to a specific micro-organism. Thus, studies focused on the formation of the intestinal microbiota and factors that modulate its composition are important for the development of approaches for colorectal cancer prevention.

Real-time fluorescence loop-mediated isothermal amplification assay for rapid and sensitive detection of Streptococcus gallolyticus subsp. gallolyticus associated with colorectal cancer

The increasing threat of Streptococcus gallolyticus subsp. gallolyticus (SGG) infections has gained considerable attention for its strong association with colorectal cancer (CRC). Herein, we proposed real-time fluorescence loop-mediated isothermal amplification (LAMP) as a novel, simple, rapid, and highly sensitive assay for identifying SGG for the first time. This assay was capable of detecting SGG with initial DNA concentrations ranging from 10² to 10⁸ copies per microliter, under isothermal conditions within 30 min via real-time fluorescence monitoring. Our method was tested for specific identification of SGG strains without cross-reaction with other Streptococcus gallolyticus subspecies and Escherichia coli. The developed LAMP shows a superior performance with shorter time and higher sensitivity compared with conventional polymerase chain reaction (PCR). Significantly, this proposed approach was successfully applied for detecting SGG in clinical urine samples, which is non-invasive diagnosis, showing excellent accuracy and reliability to discriminate healthy controls and CRC patients. For comparison, these samples were also tested against PCR assay. These results yielded an analytical sensitivity of 100% and a specificity of 100% for SGG testing using LAMP. The findings suggest LAMP can be employed for detecting SGG infections which is useful for diagnosis and screening of CRC.

Neurological symptoms and mortality associated with Streptococcus gallolyticus subsp. pasteurianus in calves

Suppurative meningitis-meningoencephalitis (M-ME) is a sporadic disease in neonatal ungulates and only a few studies have reported the involvement of Streptococcus bovis/Streptococcus equinus complex (SBSEC) members in bovine neonatal M-ME. The SBSEC taxonomy was recent revised and previous biotype II/2 was reclassified as S. gallolyticus subsp. pasteurianus (SGP). The aim of this study was to describe a case of fatal neonatal neurological syndrome associated with SGP in calves. Ten calves were monitored because of neurological hyperacute symptoms associate with bilateral hypopyon and death. They were not fed with maternal colostrum; two of them died and were subjected to bacteriological, histopathological and biomolecular analysis as well as antibiotic susceptibility test. Both animals presented lesions mostly concentrated to meninges and brain and had bilateral hypopyon. Nine strains isolated in purity from brain, ocular humors and colon were identified as S. bovis group by using the API Strep system and as S. gallolyticus by using the 16S rRNA sequence. Two of these strains where subjected to WGS analysis that confirmed the sub-species identification and the clonality of the two SGP strains. The strains were found resistant to OT, SXT, MTZ and EN and susceptible to AMP, AMC, KZ and CN. We hypothesized that the syndrome observed could be due to the lack of maternal colostrum feeding. A timely and precise diagnosis could have likely prevented the death of the calves and, since the zoonotic potential of SBSECs members is known, accurate and rapid identification is required.

Diet, Microbiome, and Epigenetics in the Era of Precision Medicine

Precision medicine is a revolutionary approach to disease prevention and treatment that takes into account individual differences in lifestyle, environment, and biology. The US National Institutes of Health has recently launched The All of Us Research Program (2016) to extend precision medicine to all diseases by building a national research cohort of one million or more US participants. This review is limited to how the human microbiome factors into precision medicine from the applied aspect of preventing and managing cancer. The Precision Medicine Initiative was established in an effort to address particular characteristics of each person with the aim to increase the effectiveness of medical interventions in terms of prevention and treatment of multiple diseases including cancer. Many factors contribute to the response to an intervention. The microbiome and microbially produced metabolites are capable of epigenetic modulation of gene activity, and can influence the response through these mechanisms. The fact that diet has an impact on microbiome implies that it will also affect the epigenetic mechanisms involving microbiota. In this chapter, we review some major epigenetic mechanisms, notably DNA methylation, chromatin remodeling and histone modification, and noncoding RNA, implicated in cancer prevention and treatment. Several examples of how microbially produced metabolites from food influence cancer risk and treatment response through epigenetic mechanisms will be discussed. Some challenges include the limited understanding of how diet shapes the microbiome and how to best evaluate those changes since both, diet and the microbiota, exhibit daily and seasonal variations. Ongoing research seeks to understand the relationship between the human microbiome and multiple diseases including cancer.

The presence of bacteria varies between colorectal adenocarcinomas, precursor lesions and non-malignant tissue

BACKGROUND

A causal association has been suggested between certain bacteria and colorectal cancer (CRC). Only a few studies have, however, investigated the presence of these bacteria directly in colon tissue with conflicting results. It is thus uncertain which role they may have in prognosis and carcinogenesis of CRC.

METHODS

Formalin-fixed and paraffin-embedded (FFPE) colorectal tissue samples from patients diagnosed with colorectal cancer (CRC)(tumor and paired normal tissue, n = 99), adenomas (n = 96), or diverticular disease (n = 104) were tested for the presence and bacterial load of Streptococcus gallolyticus (S. gallolyticus), Fusobacterium nucleatum (F. nucleatum), and Bacteroides fragilis (B. fragilis) using quantitative PCR. A subsequent broader search was conducted on a subset of samples using 16S ribosomal RNA gene sequencing. Finally, to evaluate the prognostic value, the bacterial status was compared to patient outcome.

RESULTS

S. gallolyticus was not detected by qPCR in any of the investigated tissue samples and F. nucleatum and B. fragilis were found to be equally distributed in tumors, paired normal tissue, and diverticula, but significantly less present in adenomas compared to both tumors and diverticula. Neither, F. nucleatum nor B. fragilis status affected the five-year prognosis of the patients. The 16S rRNA gene sequencing data revealed that tumors were associated with the Prevotella genus while conversely adenomas and diverticula were associated with Acinetobacter genus.

CONCLUSION

These findings do not support a role of F. nucleatum or B. fragilis during colorectal beginning, while S. gallolyticus was not implicated in the colorectal tissue of a Danish population. A potential role of the bacterial genera Prevotella and Acinetobacter was indicated, and requires further investigations.

Identification of candidate biomarkers associated with apoptosis in melanosis coli: GNG5, LPAR3, MAPK8, and PSMC6

Purpose: Melanosis coli (MC) is a disorder of pigmentation of the wall of the colon, often identified at the time of colonoscopy. The aim of the present study is to identify candidate biomarkers for MC. Methods: The transcriptome data for MC (GSE78933) with five MC tissues and five corresponding normal tissues is obtained from the NCBI Gene Expression Omnibus (GEO) database. R/Bioconductor package limma was used to screen differently expressed genes (DEGs). ClueGO of cytoscape was applied for Gene Ontology (GO) functional and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. Based on STRING V10 database, protein–protein interaction (PPI) network was constructed. The pathological tissue and normal tissue from 23 MC patients and 23 controls were collected, respectively. The relative expression of hub nodes was detected by qRT-PCR and Western blot. For regulating the expression of these genes, overexpression vector was constructed or siRNA transfection was used. Finally, apoptosis was detected by flow cytometry. Results: Total 1342 DEGs were screened, including 786 up-regulated and 556 down-regulated genes. These genes were mainly enriched in stimulatory C-type lectin receptor signaling pathway, polysaccharide biosynthetic process, intracellular, and oxidative phosphorylation. PPI network was then constructed with 426 DEGs and 895 interactions. Thereinto, G-protein subunit γ 5 (GNG5), lysophosphatidic acid receptor 3 (LPAR3), mitogen-activated protein kinase 8 (MAPK8), NHP2L1, proteasome 26S subunit, ATPase 6 (PSMC6), and phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit β (PIK3CB) were hub nodes with higher degree. RT-PCR and Western blot results showed that GNG5, LPAR3, MAPK8, and PSMC6 were differently expressed with significance. The expression of these screened genes is also related with cell apoptosis. Conclusion: GNG5, LPAR3, MAPK8, and PSMC6 might be candidate biomarkers associated with apoptosis in MC.

Correlation between Streptococcus bovis bacteremia and density of cows in Galicia, northwest of Spain

BACKGROUND

There are few data on the epidemiology of infections caused by Streptococcus bovis (Sb). Some studies suggest that both residence in rural areas and contact with livestock could be potential risk factors.

METHODS

We performed a retrospective study for the period 2005-2016 of all cases of bacteremia caused by Sb in Galicia (a region in the northwest of Spain). The association between the incidence rate of Sb bacteremia and the number of cattle by province and district was analyzed.

RESULTS

677 cases were included with a median age of 76 years, 69.3% males. The most frequent infections were endocarditis (234 cases, 34.5%), primary bacteremia (213 cases, 31.5%) and biliary infection (119 cases, 17.5%). In 252 patients, colon neoplasms were detected (37.2%). S. gallolyticus subsp. gallolyticus was the predominant species (52.3%). Mortality was 15.5% (105 cases). The annual incidence rate was 20.2 cases/10⁶ inhabitants and was correlated with the density of cattle (p < 0.001), but not with rurality. When comparing the two provinces with a strong predominance of rural population, but with important differences in the number of cattle, such as Orense and Lugo, with 6% and 47.7% of Galician cattle, respectively, the rates were very different: 15.8 and 43.6 cases/10⁶, respectively, with an RR of 2.7 (95% CI, 2.08-3.71). Some districts of the province of Lugo had rates higher than 100 cases/10⁶ inhabitants.

CONCLUSIONS

Our study shows a significant correlation between the rates of Sb bacteremia and cattle density, suggesting a possible transmission of Sb from cows to people.

Microbes involving in carcinogenesis; growing state of the art

Lateral gene transfer (LGT) has been demonstrated as a transfer process of novel genes between different species. LGT proceedings are occurring between microbes and plants, as well as between microbes and animals. New evidence demonstrates that bacterial insertional mutagenesis may occur in cancer cells. Due to the important role of genetic changes in the increase of cell proliferation and cancer development, we reviewed the effects of microbial-animal LGT in human oncogenesis. In addition, viral DNA can induce cancer development by random insertion into cancer-related genes or by inducing translocations. In conclusion, growing evidence shows the contribution of the microbial genome in cancer and autoimmune disease.

Association Between Bacteremia From Specific Microbes and Subsequent Diagnosis of Colorectal Cancer

BACKGROUND & AIMS

Colorectal cancer (CRC) development has been associated with increased proportions of Bacteroides fragilis and certain Streptococcus, Fusobacterium, and Peptostreptococcus species in the intestinal microbiota. We investigated associations between bacteremia from specific intestinal microbes and occurrence of CRC.

METHODS

We performed a retrospective study after collecting data on 13,096 adult patients (exposed group) in Hong Kong hospitalized with bacteremia (identified by blood culture test) without a previous diagnosis of cancer from January 1, 2006 through December 31, 2015. We collected data on intestinal microbes previously associated with CRC (genera Bacteroides, Clostridium, Filifactor, Fusobacterium, Gemella, Granulicatella, Parvimonas, Peptostreptococcus, Prevotella, Solobacterium, and Streptococcus). Clinical information, including patient demographics, comorbid medical conditions, date of bacteremia, and bacterial species identified, were collected. The incidence of biopsy-proved CRC was compared between the exposed and unexposed (patients without bacteremia matched for age, sex, and comorbidities) groups.

RESULTS

The risk of CRC was increased in patients with bacteremia from B fragilis (hazard ratio [HR] = 3.85, 95% CI = 2.62-5.64, P = 5.5 × 10^-12) or Streptococcus gallolyticus (HR = 5.73, 95% CI = 2.18-15.1, P = 4.1 × 10^-4) compared with the unexposed group. In addition, the risk of CRC was increased in patients with bacteremia from Fusobacterium nucleatum (HR = 6.89, 95% CI = 1.70-27.9, P = .007), Peptostreptococcus species (HR = 3.06, 95% CI = 1.47-6.35, P = .003), Clostridium septicum (HR = 17.1, 95% CI = 1.82-160, P = .013), Clostridium perfringens (HR = 2.29, 95% CI = 1.16-4.52, P = .017), or Gemella morbillorum (HR = 15.2, 95% CI = 1.54-150, P = .020). We observed no increased risk in patients with bacteremia caused by microbes not previously associated with colorectal neoplasms.

CONCLUSIONS

In a retrospective analysis of patients hospitalized for bacteremia, we associated later diagnosis of CRC with B fragilis and S gallolyticus and other intestinal microbes. These bacteria might have entered the bloodstream from intestinal dysbiosis and perturbed barrier function. These findings support a model in which specific members of the intestinal microbiota promote colorectal carcinogenesis. Clinicians should evaluate patients with bacteremia from these species for neoplastic lesions in the colorectum.

Colorectal cancer-associated Streptococcus infantarius subsp. infantarius differ from a major dairy lineage providing evidence for pathogenic, pathobiont and food-grade lineages

Streptococcus infantarius subsp. infantarius (Sii), a member of the Streptococcus bovis/Streptococcus equinus complex (SBSEC), predominates as dairy-adapted and non-adapted variants in fermented dairy products (FDP) in East and West Africa. Epidemiologic data suggest an association with colorectal cancer for most SBSEC members, including Sii from Kenyan patients. Phylogenetic relationships of East African human (EAH) isolates to those of dairy and pathogenic origin were analysed to better estimate potential health implications via FDP consumption. The MLST-derived population structure was also evaluated to provide host, disease, geography and dairy adaptation associations for 157 SBSEC isolates, including 83 novel Sii/SBSEC isolates of which 40 originated from Kenyan colonoscopy patients. Clonal complex (CC) 90 was delineated as potential pathogenic CC for Sii. Single EAH, West African dairy (WAD), food and animal Sii isolates clustered within CC-90, suggesting a potential link to pathogenic traits for CC-90. The majority of EAH and WAD Sii were clustered in a shared clade distinct from CC-90 and East African dairy (EAD) isolates. This indicates shared ancestry for the EAH and WAD clade and limitations to translate disease associations of EAH and CC-90 to EAD Sii, which could support the separation of pathogenic, pathobiont/commensal and food lineages.

Clinical applications of gut microbiota in cancer biology

The involvement of microorganisms in cancer has been increasing recognized. Collectively, microorganisms have been estimated to account for ∼20% of all cancers worldwide. Recent advances in metagenomics and bioinformatics have provided new insights on the microbial ecology in different tumors, pinpointing the roles of microorganisms in cancer formation, development and response to treatments. Furthermore, studies have emphasized the importance of host-microbial and inter-microbial interactions in the cancer microbiota. These studies have not only revolutionized our understanding of cancer biology, but also opened up new opportunities for cancer prevention, diagnosis, prognostication and treatment. This review article aims to summarize the microbiota in various cancers and their treatments, and explore clinical applications for such relevance.