Differences between endocarditis caused by Streptococcus bovis and Enterococcus spp. and their association with colorectal cancer

Gut Microbiota and Colorectal Cancer: A Balance Between Risk and Protection

The gut microbiome, a complex community of microorganisms residing in the intestinal tract, plays a dual role in colorectal cancer (CRC) development, acting both as a contributing risk factor and as a protective element. This review explores the mechanisms by which gut microbiota contribute to CRC, emphasizing inflammation, oxidative stress, immune evasion, and the production of genotoxins and microbial metabolites. Fusobacterium nucleatum, Escherichia coli (pks+), and Bacteroides fragilis promote tumorigenesis by inducing chronic inflammation, generating reactive oxygen species, and producing virulence factors that damage host DNA. These microorganisms can also evade the antitumor immune response by suppressing cytotoxic T cell activity and increasing regulatory T cell populations. Additionally, microbial-derived metabolites such as secondary bile acids and trimethylamine-N-oxide (TMAO) have been linked to carcinogenic processes. Conversely, protective microbiota, including Lactobacillus, Bifidobacterium, and Faecalibacterium prausnitzii, contribute to intestinal homeostasis by producing short-chain fatty acids (SCFAs) like butyrate, which exhibit anti-inflammatory and anti-carcinogenic properties. These beneficial microbes enhance gut barrier integrity, modulate immune responses, and inhibit tumor cell proliferation. Understanding the dynamic interplay between pathogenic and protective microbiota is essential for developing microbiome-based interventions, such as probiotics, prebiotics, and fecal microbiota transplantation, to prevent or treat CRC. Future research should focus on identifying microbial biomarkers for early CRC detection and exploring personalized microbiome-targeted therapies. A deeper understanding of host-microbiota interactions may lead to innovative strategies for CRC management and improved patient outcomes.

Impact of gut microbiota and its metabolites on immunometabolism in colorectal cancer

Colorectal cancer (CRC) is highly prevalent, accounting for approximately one-tenth of cancer cases and deaths globally. It stands as the second most deadly and third most common cancer type. Although the gut microbiota has been implicated in CRC carcinogenesis for the last several decades, it remains one of the least understood risk factors for CRC development, as the gut microbiota is highly diverse and variable. Many studies have uncovered unique microbial signatures in CRC patients compared with healthy matched controls, with variations dependent on patient age, disease stage, and location. In addition, mechanistic studies revealed that tumor-associated bacteria produce diverse metabolites, proteins, and macromolecules during tumor development and progression in the colon, which impact both cancer cells and immune cells. Here, we summarize microbiota's role in tumor development and progression, then we discuss how the metabolic alterations in CRC tumor cells, immune cells, and the tumor microenvironment result in the reprogramming of activation, differentiation, functions, and phenotypes of immune cells within the tumor. Tumor-associated microbiota also undergoes metabolic adaptation to survive within the tumor environment, leading to immune evasion, accumulation of mutations, and impairment of immune cells. Finally, we conclude with a discussion on the interplay between gut microbiota, immunometabolism, and CRC, highlighting a complex interaction that influences cancer development, progression, and cancer therapy efficacy.

Native Infective Endocarditis: A State-of-the-Art-Review

Native valve infective endocarditis (NVE) is a global phenomenon, defined by infection of a native heart valve and involving the endocardial surface. The causes and epidemiology of the disease have evolved in recent decades, with a doubling of the average patient age. A higher incidence was observed in patients with implanted cardiac devices that can result in right-sided infection of the tricuspid valve. The microbiology of the disease has also changed. Previously, staphylococci, which are most often associated with health-care contact and invasive procedures, were the most common cause of the disease. This has now been superseded by streptococci. While innovative diagnostic and therapeutic strategies have emerged, mortality rates have not improved and remain at 30%, which is higher than that for many cancer diagnoses. The lack of randomized trials and logistical constraints impede clinical management, and long-standing controversies such as the use of antibiotic prophylaxis persist. This state of the art review addresses clinical practice, controversies, and strategies to combat this potentially devastating disease. A multidisciplinary team will be established to provide care for patients with presumptive NVE. The composition of the team will include specialists in cardiology, cardiovascular surgery, and infectious disease. The prompt administration of combination antimicrobial therapy is essential for effective NVE treatment. Additionally, a meticulous evaluation of each patient is necessary in order to identify any indications for immediate valve surgery. With the intention of promoting a more comprehensive understanding of the procedural management of native infective endocarditis and to furnish clinicians with a reference, the current evidence for the utilization of distinct strategies for the diagnosis and treatment of NVE are presented.

Exploring the Role of the Gut Microbiota in Colorectal Cancer Development

Colorectal cancer is currently a public health concern due to its high incidence, morbidity, and mortality rates. Researchers have identified the intestinal microbiome as a crucial factor in the development of this disease. Currently, specialized literature data support the role of the microbiota in both the development of colorectal cancer and resistance to oncological therapies. Therefore, studying the composition of the gut microbiome can aid in creating risk assessment tools to identify specific populations that would benefit from tailored screening approaches. Also, manipulation of the intestinal microbiome can be useful in improving the response to chemotherapy or immunotherapy. Identifying the pathogenic mechanisms responsible for this causal link can aid in the discovery of novel treatment targets. This article will provide the latest information regarding the influence of the intestinal microbiota on the development and progression of colorectal cancer.

A pathogenicity locus of Streptococcus gallolyticus subspecies gallolyticus

Streptococcus gallolyticus subspecies gallolyticus (Sgg) is known to be strongly associated with colorectal cancer (CRC). Recent functional studies further demonstrated that Sgg actively stimulates CRC cell proliferation and promotes the development of colon tumors. However, the Sgg factors important for the pro-proliferative and pro-tumor activities of Sgg remain unclear. Here, we identified a chromosomal locus in Sgg strain TX20005. Deletion of this locus significantly reduced Sgg adherence to CRC cells and abrogated the ability of Sgg to stimulate CRC cell proliferation. Thus, we designate this locus as the Sgg pathogenicity-associated region (SPAR). More importantly, we found that SPAR is important for Sgg pathogenicity in vivo. In a gut colonization model, mice exposed to the SPAR deletion mutant showed significantly reduced Sgg load in the colonic tissues and fecal materials, suggesting that SPAR contributes to the colonization capacity of Sgg. In a mouse model of CRC, deletion of SPAR abolished the ability of Sgg to promote the development of colon tumors growth. Taken together, these results highlight SPAR as a critical pathogenicity determinant of Sgg.

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.

Infective Endocarditis in the Elderly: Challenges and Strategies

The specific management of infective endocarditis (IE) in elderly patients is not specifically addressed in recent guidelines despite its increasing incidence and high mortality in this population. The term "elderly" corresponds to different ages in the literature, but it is defined by considerable comorbidity and heterogeneity. Cancer incidence, specifically colorectal cancer, is increased in older patients with IE and impacts its outcome. Diagnosis of IE in elderly patients is challenging due to the atypical presentation of the disease and the lower performance of imaging studies. Enterococcal etiology is more frequent than in younger patients. Antibiotic treatment should prioritize diminishing adverse effects and drug interactions while maintaining the best efficacy, as surgical treatment is less commonly performed in this population due to the high surgical risk. The global assessment of elderly patients with IE, with particular attention to frailty and geriatric profiles, should be performed by multidisciplinary teams to improve disease management in this population.

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.

Bacterial and Parasitic Pathogens as Risk Factors for Cancers in the Gastrointestinal Tract: A Review of Current Epidemiological Knowledge

The oncogenic potential of viral infections is well established and documented for many years already. However, the contribution of (commensal) bacteria and parasites to the development and progression of cancers has only recently gained momentum, resulting in a rapid growth of publications on the topic. Indeed, various bacteria and parasites have been suggested to play a role in the development of gastrointestinal cancer in particular. Therefore, an overview of the current epidemiological knowledge on the association between infections with bacteria and parasites and cancers of the gastrointestinal tract is needed. In this review, we summarized the methodological characteristics and main results of epidemiological studies investigating the association of 10 different bacteria (Bacteroides fragilis, Campylobacter spp., Clostridium spp., Enterococcus faecalis, Escherichia coli, Fusobacterium nucleatum, Porphyromonas gingivalis, non-typhoidal Salmonella, Salmonella Typhi, and Streptococcus spp.) and three parasites (Cryptosporidium spp., Schistosoma spp., and Strongyloides stercoralis) with gastrointestinal cancer. While the large body of studies based on microbiome sequencing provides valuable insights into the relative abundance of different bacterial taxa in cancer patients as compared to individuals with pre-malignant conditions or healthy controls, more research is needed to fulfill Koch's postulates, possibly making use of follow-up data, to assess the complex role of bacterial and parasitic infections in cancer epidemiology. Studies incorporating follow-up time between detection of the bacterium or parasite and cancer diagnosis remain valuable as these allow for estimation of cause-effect relationships.

Streptococcus gallolyticus endocarditis on a prosthetic tricuspid valve: a case report and review of the literature

Background

Streptococcus gallolyticus subspecies gallolyticus is a known pathogen that causes infective endocarditis, and most cases involve the left heart valves. We present the first reported case of prosthetic tricuspid valve endocarditis caused by this microorganism. Relevant literature is reviewed.

Case presentation

A 67-year-old Jewish female with a history of a prosthetic tricuspid valve replacement was admitted to the emergency department because of nonspecific complaints including effort dyspnea, fatigue, and a single episode of transient visual loss and fever. No significant physical findings were observed. Laboratory examinations revealed microangiopathic hemolytic anemia and a few nonspecific abnormalities. Transesophageal echocardiogram demonstrated a vegetation attached to the prosthetic tricuspid valve. The involved tricuspid valve was replaced by a new tissue valve, and Streptococcus gallolyticus subspecies gallolyticus was grown from its culture. Prolonged antibiotic treatment was initiated.

Conclusions

Based on this report and the reviewed literature, Streptococcus gallolyticus should be considered as a rare but potential causative microorganism in prosthetic right-sided valves endocarditis. The patient’s atypical presentation emphasizes the need for a high index of suspicion for the diagnosis of infective endocarditis.

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.

Enterococcal bacteraemia 'silent but deadly': a population-based cohort study

BACKGROUND

The high mortality rate of patients with enterococcal infections has been shown to be associated with the severity of underlying comorbidities.

AIMS

To characterise the epidemiology, clinical characteristics, outcomes and predictors of mortality in patients with enterococcal bacteraemia.

METHODS

This was a retrospective cohort study of all enterococcal bacteraemia episodes in the Barwon region between January 2010 and March 2017. We assessed the epidemiology, clinical characteristics, outcomes and predictors of mortality using descriptive statistics and simple and multiple logistic regression analyses.

RESULTS

The incidence of enterococcal bacteraemia was 19.9/100 000 person-years. Males comprised 68.4%, and the median age was 71 years. Common comorbidities were gastrointestinal tract disease, urological disease, malignancies and cardiovascular disease. Infective endocarditis was observed in 15% of patients, and 1 of 27 also had colorectal cancer. Twelve patients referred for colonoscopy demonstrated previously undiagnosed colorectal neoplasia in 75% of these cases. The 30-day and 1-year mortality rates were 11.7 and 40.2% respectively. Sixty-nine cases with vancomycin-resistant Enterococcus were observed. Multiple logistic regression suggested that the presence of underlying urological malignancy (adjusted odds ratio = 3.57, 95% confidence intervals = 1.10-11.65, P = 0.035) and colorectal cancer (adjusted odds ratio = 4.47, 95% confidence intervals = 1.36-14.66, P = 0.014) were significant predictors of 1-year mortality.

CONCLUSIONS

Microbiological cure was inversely associated with 30-day mortality. The presence of underlying urological and colorectal malignancy was a predictor of 1-year mortality. We identified the importance of evaluating patients with Enterococcus faecalis bacteraemia for underlying colorectal neoplasia. Routine colonoscopy is recommended in patients with E. faecalis bacteraemia or infective endocarditis with an unclear source of infection.

Enterococcal infective endocarditis is a marker of current occult or future incident colorectal neoplasia

BACKGROUND

Few studies suggest an association between Enterococcal infective endocarditis (EIE) and colorectal disease, including colorectal neoplasia (CRN) and colorectal cancer (CRC). In this study, we analyze differences in prevalence, risk factors and outcome of CRN and CRC between EIE and Streptococcus gallolyticus infective endocarditis (SGIE).

METHODS

Single center, observational study of 166 patients with definite EIE or SGIE. Clinical data were collected prospectively in a standardized IE protocol. Colonoscopy data were collected retrospectively on 90 patients.

RESULTS

85 patients had EIE, 81 SGIE. EIE patients had a higher rate of prior cancer (20% vs 6%) and health-care associated infection (12% vs 1%), but similar mortality than SGIE. Colonoscopy performed in 90 patients showed intestinal diseases in 30 of 42 (71%) EIE patients vs. 40 of 48 (83%) SGIE patients (p = 0.174), with a predominance of CRN. Among 78 patients who underwent colonoscopy after IE diagnosis, no difference between EIE and SGIE was observed in the rate of non-neoplastic lesions (48% vs 47%), benign (32% vs 40%) or malignant (13% vs 15%) neoplastic lesions. Adverse events during colonoscopy were uncommon, although a careful handling of anticoagulation was required.

CONCLUSIONS

EIE seems to be associated with colorectal disease, including colorectal neoplasia and colorectal cancer, to the same extent as SGIE. EIE should be considered a marker of colorectal neoplasia, even in patients with a clear health-care related acquisition. Colonoscopy is generally safe in EIE patients, and should be considered to early diagnose and treat colorectal disease.

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.

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 SggT7SST05). We showed that core genes within the SggT7SST05 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 SggT7SST05 is functional. Deletion of SggT7SST05 (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 SggT7SST05-secreted factors are responsible for the pro-proliferative activity of Sgg, whereas Sgg adherence to host cells requires both SggT7SST05-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 SggT7SST05-mediated activities are directly involved in the promotion of colon tumors. Taken together, these results reveal SggT7SST05 as a previously unrecognized pathogenicity determinant for Sgg colonization of the colon and promotion of colon tumors.

Streptococcus bovis Contributes to the Development of Colorectal Cancer via Recruiting CD11b⁺TLR-4⁺ Cells

Background

An increasing number of studies have demonstrated that Streptococcus bovis and its concomitant inflammatory factors concentrate in the intestine in colorectal cancer (CRC). However, the molecular mechanism of S. bovis on colorectal tumorigenesis remains unclear. This study aimed to explore the role of S. bovis in carcinogenesis and its potential mechanism in CRC of mice orally pretreated with S. bovis.

Material/Methods

The colons of experimental mice were collected and evaluated for the extent of neoplasm. In addition, comparative feces DNA sequencing was adopted to verify the abundance change of S. bovis during the progression of CRC in patients.

Results

The results of this study found that S. bovis is more likely to be present at higher levels in patients with progressive colorectal carcinoma compared to those adenoma patients and healthy volunteers (P<0.05). Pretreatment with S. bovis aggravated tumor formation in mice, resulting in more substantial and a higher number of tumor nodes (P<0.05). A cytokine expression pattern with increased levels of IL-6, Scyb1, Ptgs2, IL-1β, TNF, and Ccl2 was detected in S. bovis pretreated CRC mice (all P<0.05). Furthermore, S. bovis recruited myeloid cells, especially CD11b⁺TLR-4⁺ cells, which could promote pro-tumor immunity in the tumor microenvironment (P<0.05).

Conclusions

Collectively, our study indicates that S. bovis may induce a suppressive immunity that is conducive to CRC by recruiting tumor-infiltrating CD11b⁺TLR-4⁺ cells. In conclusion, S. bovis contributes to colorectal tumorigenesis via recruiting CD11b⁺TLR-4⁺ cells.

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.

Western Immunoblotting for the Diagnosis of Enterococcus faecalis and Streptococcus gallolyticus Infective Endocarditis

Blood culture-negative endocarditis (BCNE) remains a diagnostic challenge. In our center, despite a systematic and exhaustive microbiological diagnostics strategy, 22% of patients with BCNE remain without an identified etiology. In an effort to determine the relevance of using Western blot (WB) for the etiological diagnosis of BCNE in patients with early antibiotic use, we developed specific assays for the major infective endocarditis (IE) causative agents, namely, Staphylococcus aureus, Enterococcus faecalis, Streptococcus anginosus, and Streptococcus gallolyticus. Our technique was effective to identify the antigenic profiles of the four tested agents, but cross-reactions with S. aureus and S. anginosus antigens were frequent. A scoring method was developed for the diagnosis of E. faecalis and S. gallolyticus IE using the presence of reactivity to at least two antigenic bands for each bacterium and the positivity to at least one of the Ef300, Ef72, or Ef36 proteic bands for E. faecalis, and positivity for the two Sg75 and Sg97 proteic bands for S. gallolyticus. We tested these diagnostic criteria in a prospective cohort of 363 patients with suspected IE. Immunoblotting for the diagnosis of E. faecalis IE showed a sensitivity of 100% and a specificity of 99%. The positive and negative predictive values were 73 and 100%, respectively. Regarding S. gallolyticus infection, immunoblot had a sensitivity of 100% and a specificity of 95%. However, the positive predictive value was 22%, whereas the predictive negative value was 100%. Using WB, we identified a potential etiological agent in 4 of 14 BCNE cases with no identified pathogen. In conclusion, WB constitutes a promising and helpful method to diagnose E. faecalis or S. gallolyticus IE in patients with early antibiotic uptake and negative blood cultures.

Twenty-Year Secular Trends in Infective Endocarditis in a Teaching Hospital

Background

The purpose of this study was to analyze the secular trends of infective endocarditis in a teaching hospital between January 1996 and December 2015.

Methods

We report on a single-center retrospective study of patients with left-side valve infective endocarditis. We performed an analysis of secular trends in the main epidemiological and etiological aspects, as well as clinical outcomes, in 5 successive 4-year periods (P1 to P5).

Results

In total, 595 episodes of infective endocarditis were included, of which 76% were community-acquired and 31.3% involved prosthetic valves. Among the cases, 70% occurred in men, and the mean age (SD) was 64.1 (14.3) years. A significant increase in older patients (age ≥70 years) between P1 (15.332%) and P5 (51.9%; P < .001) was observed. The rate of infective endocarditis on biological prostheses also increased in the prosthetic group, accounting for 30% in P1 and 67.3% in P5 (P < .001). By contrast, there were significant decreases in vascular and immunological phenomena over the study period, with decreases in the presence of moderate to severe valvular insufficiency (75.9% in P1 to 52.6% in P5; P < .001) and valvular surgery (43% in P1 vs 29.6% in P5; P = .006). Finally, overall mortality was 23.9%, and although it was highest in P1, it subsequently remained stable through P2 to P5 (38% in P1 to 20% in P5; P = .004).

Conclusions

There has been a significant increase in infective endocarditis in older patients. The decrease in moderate to severe valve regurgitation at diagnosis could explain the stable mortality despite the increase in the mean age of patients over time.

Raoultella planticola Bacteremia in a Patient with Early Gastric Cancer

The patient was an 81-year-old man who was found to have bacteremia due to Raoultella planticola, which might have entered the circulation through the bile duct during the passing of a gallbladder stone. In the present case, we screened for malignancies because most cases of R. planticola bacteremia occur after trauma, invasive procedures, or in patients with malignancy (70.6%). Early gastric cancer was detected. Although the association between R. planticola bacteremia and malignancy remains speculative in the present case, it may be useful to scrutinize similar cases involving low-virulence bacteremia for possible malignancies or immune conditions.

Significance of Streptococcus gallolyticus subsp. gallolyticus Association With Colorectal Cancer

Streptococcus gallolyticus subsp. gallolyticus Sgg (formerly known as S. bovis type I) is the main causative agent of septicemia and infective endocarditis (IE) in elderly and immunocompromised persons. It belongs to the few opportunistic bacteria, which have been strongly associated to colorectal cancer (CRC). A literature survey covering a period of 40 years (1970–2010) revealed that 65% of patients diagnosed with an invasive Sgg infection had a concomitant colorectal neoplasia. Sgg is associated mainly with early adenomas and may thus constitute an early marker for CRC screening. Sgg has been described as a normal inhabitant of the rumen of herbivores and in the digestive tract of birds. It is more rarely detected in human intestinal tract (2.5–15%). Recent molecular analyses indicate possible zoonotic transmission of Sgg. Thanks to the development of a genetic toolbox and to comparative genomics, a number of factors that are important for Sgg pathogenicity have been identified. This review will highlight the role of Sgg pili in host colonization and how their phase-variable expression contributes to mitigate the host immune responses and finally their use as serological diagnostic tool. We will then present experimental data addressing the core question whether Sgg is a cause or consequence of CRC. We will discuss a few recent studies examining the etiological versus non-etiological participation of Sgg in colorectal cancer with the underlying mechanisms.

Variations among Streptococcus gallolyticus subsp. gallolyticus strains in connection with colorectal cancer

Streptococcus gallolyticus subsp. gallolyticus (Sg) has long been reported to display a strong association with colorectal cancer (CRC). It was recently demonstrated to actively promote the development of CRC, underscoring the importance of Sg in both clinical correlation and functional relevance in CRC. Here we investigated several clinical isolates of Sg in their interactions with human colon cancer cells and in mouse models. Some Sg strains were able to stimulate host cell proliferation (proliferation-promoting Sg, PP-Sg) whereas others were not (non-proliferation-promoting Sg, NP-Sg). PP-Sg strains adhered to colon cancer cells much better than NP-Sg strains, suggesting that close contact between Sg and host cells is important. In mice, PP-Sg is significantly better at colonizing the colon tissues of A/J mice compared to NP-Sg, however this difference was not observed in C57BL/6 mice, suggesting that Sg colonization of mouse colon tissues involves specific interactions between bacterial and host factors on the colonic epithelium. Finally, in an azoxymethane-induced mouse model of CRC, PP-Sg promoted tumor development whereas NP-Sg did not. These findings provide clues to the mechanism underlying the Sg-CRC association and have important implications to clinical studies that aim to correlate Sg with clinical and pathological features of CRC.

Infectious Endocarditis from Enterococcus faecalis Associated with Tubular Adenoma of the Sigmoid Colon

Introduction

Enterococcus faecalis (E. faecalis), a constituent of the gut microbiota, can be associated with both colonic lesions and endocarditis. Since this microorganism is one of the endocarditis etiological agents, there is a need for greater study in regard to the association with endocarditis and colonic lesions.

Case Presentation

This is the case description of a 53-year-old man with history of prolapse of the anterior mitral valve leaflet who was diagnosed with endocarditis by E. faecalis and treated with ampicillin and gentamicin. Upon investigation by colonoscopy, he was found to have a tubular adenoma with low grade dysplasia.

Conclusion

There are a few descriptions in scientific literature of an association between endocarditis by E. faecalis and colonic lesions. However, further studies with significant correlation between the two pathologies are required, so that proper measures can be implemented in clinical practice.

Streptococcus gallolyticus subsp. gallolyticus promotes colorectal tumor development

Streptococcus gallolyticus subsp. gallolyticus (Sg) has long been known to have a strong association with colorectal cancer (CRC). This knowledge has important clinical implications, and yet little is known about the role of Sg in the development of CRC. Here we demonstrate that Sg promotes human colon cancer cell proliferation in a manner that depends on cell context, bacterial growth phase and direct contact between bacteria and colon cancer cells. In addition, we observed increased level of β-catenin, c-Myc and PCNA in colon cancer cells following incubation with Sg. Knockdown or inhibition of β-catenin abolished the effect of Sg. Furthermore, mice administered with Sg had significantly more tumors, higher tumor burden and dysplasia grade, and increased cell proliferation and β-catenin staining in colonic crypts compared to mice receiving control bacteria. Finally, we showed that Sg is present in the majority of CRC patients and is preferentially associated with tumor compared to normal tissues obtained from CRC patients. These results taken together establish for the first time a tumor-promoting role of Sg that involves specific bacterial and host factors and have important clinical implications.

Colorectal neoplasm in cases of Clostridium septicum and Streptococcus gallolyticus subsp. gallolyticus bacteraemia

BACKGROUND

Bacteremia with Clostridium septicum (CS) and Streptococcus gallolyticus subsp. gallolyticus (SGG) have both been associated with colorectal neoplasms (CRN) and colonoscopic examination is advised, however the differences and similarities in colorectal findings are not well known.

METHODS

This is a multicenter, comparative study of patients with CS bacteremia [44 of 664 cases (6.6%) of Clostridium spp.] and SGG bacteremia [257 of 596 cases (44.2%) of S. bovis group], carried out in three hospitals from Spain. Clinical findings related to bacteremia and associated CRN were collected.

RESULTS

The main sources of infection were abdominal (77.7%) for CS bacteremia and endovascular (75%) for SGG bacteremia. CS bacteremia was more often associated with malignancies, (72.6% vs. 19.4%) and neutropenia (29.5% vs. 3.1%), and was more acute, with shock at presentation (63.6% vs. 3.9%) and higher 30-day mortality (47.7% vs. 9.7%) compared to SGG (P<0.05 for all). Both, patients with CS and SGG bacteremia often had concomitant CRN (43.1% vs. 49.8%) and most of them presented as occult CRN (73.7% vs. 91.4%; P=0.02). CS cases more often had invasive carcinomas (94.7% vs. 19.5%), location of CRN in the right colon (73.7% vs. 23.4%), larger tumor size (median 7 vs. 1.5cm), and a higher overall CRN related mortality rate (68.4% vs. 7.8%) compared to SGG cases (P<0.05 for all).

CONCLUSIONS

Both, CS and SGG bacteremia are associated with occult CRN. CS cases more often had advanced carcinomas than SGG cases, suggesting a distinct temporal association with CRN.

Relationship Between Enterococcus faecalis Infective Endocarditis and Colorectal Neoplasm: Preliminary Results From a Cohort of 154 Patients

INTRODUCTION AND OBJECTIVES

The association between Streptococcus bovis group infective endocarditis and colorectal neoplasm (CRN) is well-known. However, no studies have assessed the association between Enterococcus faecalis infective endocarditis (EFIE) and CRN. We aimed to determine whether the prevalence of CRN is higher in patients with EFIE and an unclear source of infection than in patients with EFIE and a known source of infection or in the general population.

METHODS

Retrospective analysis of a cohort of 154 patients with definite EFIE (109 with an unclear source of infection and 45 with an identified source) from 2 Spanish teaching hospitals to determine the prevalence of CRN and other colorectal diseases.

RESULTS

In the group with an unknown source of infection, 61 patients (56%) underwent colonoscopy; of these, 31 (50.8%) had CRN. Nonadvanced colorectal adenoma was detected in 22 patients (36%), advanced adenoma in 5 (8.2%), and colorectal carcinoma (CRC) in 4 (6.6%). Among patients who survived the EFIE episode with ≥ 2 years of follow-up, 1 case of CRC was subsequently diagnosed. Only 6 patients (13.3%) with an identified focus of infection underwent colonoscopy; 1 of these patients (16.7%) was diagnosed with CRN. The prevalence of adenomas was slightly higher than that of the Spanish population in the same age range, whereas that of CRC was 17-fold higher.

CONCLUSIONS

CRN was found in more than half of patients with EFIE and an unclear focus of infection who underwent colonoscopy. Colonoscopy should be recommended in patients with EFIE and an unclear source of infection.

Native Valve Streptococcus bovis Endocarditis and Refractory Transfusion Dependent Iron Deficiency Anaemia Associated with Concomitant Carcinoma of the Colon: A Case Report and Review of the Literature

Streptococcus bovis is found as a commensal organism in human gut and may become opportunistically pathogenic. Infective endocarditis is one of the commonest modes of presentation of this infection. The association between Streptococcus bovis endocarditis and colorectal cancer is well recognized. We report a case of Streptococcus bovis endocarditis along with a refractory iron deficiency anaemia associated with concomitant carcinoma of ascending colon in a 63-year-old male. Cooccurrence of these two conditions may cause a challenge in the management. Considering the strong association of colon cancer with Streptococcus bovis endocarditis, a detailed screening colonoscopy is mandatory following the diagnosis of the latter.

Streptococcus bovis septic arthritis and osteomyelitis: A report of 21 cases and a literature review

BACKGROUND

The Streptococcus bovis group (SBG) is a well-known cause of endocarditis, but its role in osteoarticular infections (OAIs) has not been well described.

METHODS

We analyzed all patients with OAIs by SBG diagnosed in our hospital (1988-2014). We selected those cases with septic arthritis and osteomyelitis, as defined according to clinical, microbiological, and imaging studies. Identification of the strains was performed by using the API 20 Strep and the GP card of the Vitek 2 system, and confirmed the identification by molecular methods. In addition, we reviewed the literature to select all cases of OAI by SBG during the period 1980-2015.

RESULTS

From the 83 cases of OAI included in the analysis (21 from our center and 62 from the literature review), 59 were osteomyelitis (57 of them spondylodiscitis) and 24 were arthritis (2 with associated spondylodiscitis). The mean age was 66.9 years, and 79.2% of the patients were men. Endocarditis (IE) was associated with 59% of the cases and this association was greater for osteomyelitis than for arthritis (78.9% vs. 13.6%; P = 0.001). OAI was a presenting symptom in 63% of the cases of IE. Colonoscopy was performed in 64 cases, which detected colorectal neoplasm (CRN) in 46 patients (71.8%), almost all asymptomatic. Some 69.5% of these neoplasm were carcinomas or advanced adenomas. The blood cultures were positive in 78.3% cases. In 45 cases, the S. bovis species was identified; in 82.2% of the cases the cause was Streptococcus gallolyticus subsp. gallolyticus. The mortality was 7.2%, which in no case was attributable to the OAI.

CONCLUSIONS

OAIs are frequently the initial manifestation of IE caused by SBG. S. gallolyticus causes most of these infections. Echocardiogram and colonoscopy are therefore mandatory, given the species' close association with IE and CRN.

Colonic carriage of Streptococcus bovis and colorectal neoplasia: a prospective 17-year longitudinal case-control study

BACKGROUND

Patients with Streptococcus bovis infective endocarditis have an increased prevalence of advanced colonic neoplasia; however, an association with fecal carriage of the organism is unclear. S. bovis has been shown to promote colonic neoplasia in preclinical studies. The aim of this study was to examine the effect of S. bovis fecal carriage on the long-term risk of colonic neoplasia.

PATIENTS AND METHODS

Patients were prospectively recruited before colonoscopy. S. bovis was detected by culture in stool, colonic fluid aspirates, and biopsies. Patients continued colonoscopic surveillance at intervals according to accepted guidelines. The National Cancer Registry was checked for diagnoses of colorectal cancer on 31 December 2014.

RESULTS

A total of 118 patients were recruited [75 (72.8%) men, aged 64.5±9.3 years] including 15 with S. bovis. The mean duration of follow-up was 190.7±123.5 months. Colonic neoplasia was detected at colonoscopy in six (40.0%) and 49 (47%) patients with and without S. bovis, respectively (P=0.78). At the end of follow-up, colorectal cancer had developed in one (6.7%) S. bovis-positive and six (5.8%) S. bovis-negative patients (P=1.00).

CONCLUSION

Fecal carriage of S. bovis at baseline is not associated with an increased long-term risk of developing colonic neoplasia in this longitudinal study.

Streptococcus bovis infectious endocarditis and occult gastrointestinal neoplasia: experience with 25 consecutive patients treated surgically

To assess the prevalence of gastrointestinal neoplasia in patients with Streptococcus bovis infectious endocarditis we performed a retrospective cohort analysis of all episodes of S. bovis infectious endocarditis treated at our institution between January 2000 through December 2014. Twenty-five patients were identified for this purpose. 12/25 patients received colonoscopy and 1/25 of the patients was assessed with CT colonography. Of the 13 who underwent colonic assessment, 11 were diagnosed with colonic neoplasms at different stages of development. In the absence of any strong contraindication, gastroenteroscopic evaluation in all patients diagnosed with S. bovis infectious endocarditis should be pursued.