Bacteraemia due to Streptococcus gallolyticus subspecies pasteurianus is associated with digestive tract malignancies and resistance to macrolides and clindamycin

A Rare Case of Meningitis Caused by Streptococcus gallolyticus subsp. pasteurianus in an Immunocompetent Young Adult

Bacterial meningitis is a life-threatening condition that is mainly caused by Streptococcus pneumoniae and Neisseria meningitis. Although Streptococcus gallolyticus subsp. pasteurianus (Sgp) is also known to cause meningitis, its frequency is quite low, especially in adults. We herein report the first immunocompetent Japanese adult patient (20-year-old woman) with bacterial meningitis caused by Sgp. The patient showed dramatic improvement after antibiotic treatment. Although previous reports have described an association between Sgp infection and an immunosuppressive status, bowel and hepatobiliary diseases, or strongyloidiasis, our case did not demonstrate any of these conditions, suggesting that Sgp can cause meningitis even in young immunocompetent adults.

Improved identification of Streptococcus bovis-Streptococcus equinus-complex species and subspecies by MALDI-TOF MS using a novel library

OBJECTIVES

To develop an in-house matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) library for improved identification of species and subspecies of the Streptococcus bovis/Streptococcus equinus-complex (SBSEC).

METHODS

A total of 236 SBSEC isolates from blood stream infections and culture collections, determined by whole genome sequencing to subspecies level, were grown in brain heart infusion broth. Mass spectra were collected using the Bruker MALDI Biotyper system after ethanol-formic acid extraction. Main spectral profiles from 117 isolates were used to create the "SBSEC-CMRS library." The remaining 119 spectra were used for evaluation of Bruker MALDI Biotyper (MBT) Compass Library Revision K (2022) and the SBSEC-CMRS library.

RESULTS

The Bruker library correctly identified species and subspecies in 72 of 119 (61 %) isolates, while the SBSEC-CMRS library identified 116 of 119 (97 %), using a cutoff score of ≥2.0.

CONCLUSIONS

The SBSEC-CMRS library showed sufficient diagnostic accuracy, and can be implemented in clinical practice for SBSEC species and subspecies identification.

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.

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.

Comparative Evaluation of Current Biochemical-, Sequencing-, and Proteomic-Based Identification Methods for the Streptococcus bovis Group

The Streptococcus bovis group (previously group D streptococci) consists of seven distinct species and subspecies. Definitive identification within the group is important, as certain organisms have been associated with gastrointestinal carcinoma, bacteremia, infective endocarditis, meningitis, biliary tract disease, and carcinoma, among others. Definitive identification, however, remains elusive due to limitations and inconsistencies across commonly used identification platforms in the United States. Here, we compared the performance of standard biochemical (Trek Gram-positive identification [GPID] plate, Vitek 2 GPID), sequencing (16S rDNA, sodA) databases (NCBI, RDP, CDC MicrobeNet), and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) platforms (Vitek MS, Bruker Biotyper MS) using a set of eight type strains representing all seven strains within the S. bovis group. Despite the evaluation of contemporary methods, no single platform was able to definitively identify all type strains within the S. bovis group. Vitek MS (85.7%, 7/8) provided the most accurate definitive identifications, followed by sodA sequencing (75%, 6/8). Vitek 2 and Bruker Biotyper RUO platforms performed the next best (62.5%, 5/8). All remaining platforms failed to adequately differentiate type strains within the S. bovis group (range, 0 to 37.5%). Laboratorians and clinicians should be aware of the identification limitations of routine testing algorithms and incorporate reflex testing, when appropriate, to platforms such as Vitek MS and/or sodA sequencing that are more able to definitively identify S. bovis group organisms. Further clinical evaluation was conducted using 65 clinical isolates from three geographically distinct U.S. institutions. Future improvements in identification platforms may reveal new clinical and epidemiological trends for members of the S. bovis group.

Prolonged Streptococcus gallolyticus subsp. pasteurianus gut colonization in healthcare workers and potential transmission role in neonatal sepsis

BACKGROUND

Streptococcus gallolyticus subsp. pasteurianus (SGSP) is a commensal in the intestinal tract and a potential pathogen of neonatal sepsis. During an 11-month period, four consecutive cases of SGSP sepsis were identified in one postnatal care unit (unit A) without evidence of vertical transmission. Therefore, we initiated this study to investigate the reservoir and mode of transmission of SGSP.

METHOD

We performed cultures of stool samples from healthcare workers in unit A and unit B (another unit without SGSP sepsis). If SGSP was positive in feces, we performed isolate pulsotyping and genotyping by using pulsed-field gel electrophoresis (PFGE) and analyzing random amplified polymorphic DNA (RAPD) patterns, respectively.

RESULTS

Five staff members in unit A showed positivity for SGSP. All samples from unit B were negative. We identified two major pulsogroups (groups C and D) by PFGE. In group D, the strains isolated from 3 consecutive sepsis patients (P1, P2 and P3) were closely related and clustered together as those from 2 staff members (C1/C2, C6). One staff (staff 4) had a direct contact history with patient (P1) confirmed to have the same clone. The last isolate of the patient in our study (P4) belonged to a distinct clone.

CONCLUSION

We found prolonged gut colonization of SGSP in healthcare workers and its epidemiological relatedness to neonatal sepsis. Fecal-oral or contact transmission is a possible route of SGSP infection. Fecal shedding among staff may be associated with neonatal sepsis in healthcare facilities.

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.

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.

Laboratory identification and clinical characteristics of Streptococcus bovis/Streptococcus equinus complex bacteremia: a retrospective, multicenter study in Hiroshima, Japan

BACKGROUND

Bacteremia due to the Streptococcus bovis/Streptococcus equinus complex (SBSEC) is associated with specific diseases, such as colorectal cancer and infective endocarditis. This study aimed to evaluate the clinical characteristics of SBSEC bacteremia and the accuracy of identification of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and phenotypic identification systems for SBSEC isolates.

METHODS

We analyzed patients with SBSEC bacteremia retrospectively between 2012 and 2019 at three hospitals in Japan. We re-identified each SBSEC isolate using sequencing superoxide dismutase (sodA) analysis, MALDI-TOF MS using the MALDI Biotyper, and phenotypic identification using the VITEK2.

RESULTS

During the study period, 39 patients with SBSEC bacteremia were identified. S. gallolyticus subsp. pasteurianus (SGSP, n = 29), S. gallolyticus subsp. gallolyticus (SGSG, n = 5), S. lutetiensis (SL, n = 4), and S. infantarius subsp. infantarius (n = 1) were identified using sodA sequencing analysis. Primary bacteremia (36%) was the most common cause of bacteremia, followed by infective endocarditis (26%) and biliary tract infections (23%). Colorectal cancer was associated significantly with SGSG bacteremia, while the sources of bacteremia were similar in each SBSEC subspecies. The MALDI Biotyper was significantly more accurate in identifying the SBSEC isolates at the subspecies level compared to the VITEK2 (92% vs. 67%, P = 0.010). In contrast, there were no significant differences in the rates of correct identification of the SBSEC isolates at the species level between the MALDI Biotyper and the VITEK2 (100% vs. 87%, P = 0.055).

CONCLUSIONS

Bacteremia with SGSG was associated with colorectal cancer, and the sources of bacteremia were similar in each SBSEC subspecies. The MALDI-TOF MS was significantly more accurate in identifying SBSEC isolates at the subspecies level than the phenotypic identification systems. The accurate identification of SBSEC isolates using the MALDI-TOF MS and phenotypic identification systems was sufficient at the species level, but it was insufficient at the subspecies level. Therefore, it may be reasonable for clinicians to perform echocardiographies and colonoscopies in all patients with SBSEC bacteremia.

Clustering of Streptococcus gallolyticus subspecies pasteurianus bacteremia and meningitis in neonates

BACKGROUND/PURPOSE

Although Streptococcus gallolyticus subspecies pasteurianus (SGSP) is a rare pathogen in children, it can cause invasive infections among neonates and infants. Herein, we report bacteremia/meningitis caused by SGSP in three neonates and review the literature on bacteremia and/or meningitis caused by this organism.

METHODS

Three neonates, referred from an obstetrics clinic within a 2-month period, presented with invasive SGSP infections. The bacterial isolates were analyzed using Bruker Biotyper MALDI-TOF, sequencing of 16S rRNA and sodA genes (encoding manganese dependent superoxide dismutase), and PCR restriction fragment length polymorphism assay of groESL gene. Molecular typing was performed to evaluate the genetic relatedness.

RESULTS

The median onset age of infection in the three neonates was 3 days (range 2-5 days). They were delivered through cesarean section in the same operation room under different doctors, and were cared for by different nurses. Patient A presented with bacteremia, patient B with bacteremia and meningitis, and patient C with meningitis. Four isolates were identified as SGSP and were susceptible to penicillin G, cefotaxime, and vancomycin. All patients were treated with ampicillin plus cefotaxime for 14 days, and no complications were observed. The molecular typing results suggested that all isolates belonged to a single clone, which indicated the possibility of an outbreak in the obstetrics clinic.

CONCLUSION

Infection by a rare pathogen such as SGSP in multiple patients belonging to a single healthcare unit indicates that detailed investigation and stringent infection control policy are necessary for preventing further outbreaks of such diseases.

Is Echocardiography Mandatory for All Streptococcus gallolyticus Subsp. pasteurianus Bacteremia?

Background

Streptococcus gallolyticus, formerly known as one of the Streptococcus bovis group, is frequently associated with endocarditis. Current guidelines recommended diagnostic work-up for endocarditis among patients with S. gallolyticus bacteremia. However, S. gallolyticus subsp. pasteurianus, was found to be associated with neonatal sepsis and liver diseases and is less commonly associated with endocarditis compared with S. gallolyticus subsp. gallolyticus. Our study aimed to identify the risk factors for S. gallolyticus subsp. pasteurianus endocarditis to help select the patients for echocardiography.

Methods

In this retrospective cohort study, medical records from all adult patients with S. gallolyticus subsp. pasteurianus isolated from blood cultures at Phramongkutklao Hospital from 2009 to 2015 were reviewed. Patients who had mixed bacteremia or missing records were excluded from the study.

Results

During the study period, S. gallolyticus subsp. pasteurianus was isolated among 106 individuals. Mean age was 66.9±15.6 years. Most patients (61.3%) were male, with cirrhosis as the most common underlying diseases (46.2%), followed by malignancy and chronic kidney disease. Most common manifestations included primary bacteremia (44.3%), followed by spontaneous bacterial peritonitis (23.6%). Infective endocarditis was found among 9 patients. No patients with cirrhosis or single blood specimen of bacteremia had endocarditis (RR 0; p-value 0.003, and RR 1.35; p-value 0.079). The common complications associated with endocarditis were acute respiratory failure (RR 4.32; p-value 0.05), whereas acute kidney injury was a protective factor (RR 0; p-value 0.01). Among 76 patients who had records of 2-year follow-up, no new diagnosis of endocarditis or malignancy was observed.

Conclusion

Among patients with S. gallolyticus subsp. pasteurianus bacteremia, echocardiography might not be needed among patients with cirrhosis and without sustained bacteremia.

Microbiological and clinical characteristics of Streptococcus gallolyticus subsp. pasteurianus infection in China

BACKGROUND

Infections by Streptococcus gallolyticus subsp. pasteurianus (SGSP) is often underestimated. Herein, the epidemiological features and resistant characteristics of SGSP in mainland China are characterized to enable a better understanding of its role in clinical infections.

METHODS

In the present work, 45 SGSP isolates were collected from the samples of bloodstream, urine, aseptic body fluid, and fetal membrane/placenta from patients in 8 tertiary general hospitals of 6 cities/provinces in China from 2011 to 2017. The identification of all isolates was performed using traditional biochemical methods, 16S rRNA and gyrB sequencing, followed by the characterization of their antibiotic resistance profiling and involved genes.

RESULTS

Among 34 non-pregnancy-related patients, 4 (4/34,11.8%) patients had gastrointestinal cancer, 10 (10/34, 29.4%) patients had diabetes, and one patient had infective endocarditis. Moreover, 11 cases of pregnant women were associated with intrauterine infection (9/11, 81.2%) and urinary tract infection (1/11, 9.1%), respectively. Except one, all other SGSP isolates were correctly identified by the BD Phoenix automated system. We found that all SGSP isolates were phenotypically susceptible to penicillin, ampicillin, cefotaxime, meropenem, and vancomycin. Forty strains (40/45, 88.9%) were both erythromycin and clindamycin-resistant, belonging to the cMLS_B phenotype, and the majority of them carried erm(B) gene (39/40, 97.5%). Although the cMLS_B/erm(B) constituted the most frequently identified phenotype/genotype combination (25/40, 62.5%) among all erythromycin-resistant cMLS_B isolates, erm(B)/erm(A), erm(B)/mef(A/E), and erm(B)/erm(T) was detected in 7, 4, and 3 isolates, respectively. Furthermore, 43 strains (43/45, 95.6%) were tetracycline-resistant, and out of these, 39 strains (39/45, 86.7%) carried tet(L), 27(27/45, 60.0%) strains carried tet(O), and 7 (7/45, 15.6%) strains carried tet(M), alone or combined, respectively. All erythromycin-resistant isolates were also resistant to tetracycline.

CONCLUSIONS

It is important to study and draw attention on SGSP, an underreported opportunistic pathogen targeting immunodeficient populations, notably elderly subjects, pregnant women and neonates.

An Overview on Streptococcus bovis/Streptococcus equinus Complex Isolates: Identification to the Species/Subspecies Level and Antibiotic Resistance

Streptococcus bovis/Streptococcus equinus complex (SBSEC), a non-enterococcal group D Streptococcus spp. complex, has been described as commensal bacteria in humans and animals, with a fecal carriage rate in humans varying from 5% to over 60%. Among streptococci, SBSEC isolates represent the most antibiotic-resistant species—with variable resistance rates reported for clindamycin, erythromycin, tetracycline, and levofloxacin—and might act as a reservoir of multiple acquired genes. Moreover, reduced susceptibility to penicillin and vancomycin associated with mobile genetic elements have also been detected, although rarely. Since the association of SBSEC bacteremia and colon lesions, infective endocarditis and hepatobiliary diseases has been established, particularly in elderly individuals, an accurate identification of SBSEC isolates to the species and subspecies level, as well as the evaluation of antibiotic resistance, are needed. In this paper, we reviewed the major methods used to identify SBSEC isolates and the antimicrobial resistance rates reported in the scientific literature among SBSEC species.

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.

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.

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

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

Antimicrobial Resistance in Streptococcus spp

The genus Streptococcus includes Gram-positive organisms shaped in cocci and organized in chains. They are commensals, pathogens, and opportunistic pathogens for humans and animals. Most Streptococcus species of veterinary relevance have a specific ecological niche, such as S. uberis, which is almost exclusively an environmental pathogen causing bovine mastitis. In contrast, S. suis can be considered as a true zoonotic pathogen, causing specific diseases in humans after contact with infected animals or derived food products. Finally, Streptococcus species such as S. agalactiae can be sporadically zoonotic, even though they are pathogens of both humans and animals independently. For clarification, a short taxonomical overview will be given here to highlight the diversity of streptococci that infect animals. Several families of antibiotics are used to treat animals for streptococcal infections. First-line treatments are penicillins (alone or in combination with aminoglycosides), macrolides and lincosamides, fluoroquinolones, and tetracyclines. Because of the selecting role of antibiotics, resistance phenotypes have been reported in streptococci isolated from animals worldwide. Globally, the dynamic of resistance acquisition in streptococci is slower than what is experienced in Enterobacteriaceae, probably due to the much more limited horizontal spread of resistance genes. Nonetheless, transposons or integrative and conjugative elements can disseminate resistance determinants among streptococci. Besides providing key elements on the prevalence of resistance in streptococci from animals, this article will also largely consider the mechanisms and molecular epidemiology of the major types of resistance to antimicrobials encountered in the most important streptococcal species in veterinary medicine.

Streptococcus bovis new taxonomy: does subspecies distinction matter?

Bacteremia with Streptococcus bovis/equinus complex strains is associated with hepatobiliary disease, colorectal lesions (CL), and infective endocarditis (IE). This study addressed the clinical significance of subspecies distinction of previously designated S. bovis blood culture isolates according to the updated nomenclature. During 2002-2013, all blood culture isolates previously designated as S. bovis were recultured and identified using 16S rRNA gene sequencing and MALDI-TOF (Bruker BioTyper and Vitek MS, bioMérieux). Clinical data of patients aged ≥18 years were reviewed. A review of four recent case series was performed as well. Forty blood isolates were identified using 16S rRNA sequencing. Twenty-six bacteremic patients had S. gallolyticus ssp. pasteurianus, six had S. gallolyticus ssp. gallolyticus, two had S. gallolyticus ssp. macedonicus, and six had S. infantarius bacteremia. Species diagnosis using Vitek and bioMérieux MALDI-TOF technology was applicable in 37 and 36 samples, respectively, and was successful in all samples (100 %). Subspecies identification was confirmed in 30 (83 %) samples (as compared with 16S rRNA sequencing detection). IE was diagnosed in 22 (59 %) patients and CL in 8 (20 %) patients. Both complications were associated with all subspecies. Combining our results with those of four recent series resulted in, overall, 320 bacteremic cases, of which 88 (28 %) had CL and 66 (21 %) had IE. All 'bovis/equinus' complex subspecies were associated with CL or IE. From a clinical point of view, species diagnosis using MALDI-TOF MS should suffice to warrant consideration of transesophageal echocardiography and colonoscopy.

Identification, antimicrobial resistance and molecular characterization of the human emerging pathogen Streptococcus gallolyticus subsp. pasteurianus

This study aimed to retrospectively identify 22Streptococcus bovis clinical strains based on the new taxonomy, as well as to investigate their antibiotic-resistance and clonality. Strains were identified by Phoenix100 system, 16S rRNA sequencing, and two MALDI-TOF MS platforms (Bruker Biotyper, Vitek MS). Antibiotic resistance was determined both phenotypically and genotypically, and clonality was assessed by PFGE. Most of strains (63.6%) were isolated from urine, and diabetes was the most common underlying disease (31.8%). Phoenix100 system revealed all strains belonged to biotype II, and 16S rRNA sequencing identified all strains as S. gallolyticus subsp pasteurianus (SGSP). Although both MALDI-TOF MS systems correctly identified isolates to the species level, only Bruker Biotyper accurately identified to the subspecies level. Erythromycin-resistant strains (31.8%) were also clindamycin-resistant and positive for erm(B). Strains resistant to tetracycline (68.2%) were also resistant to erythromycin. PFGE showed high genetic variability identifying 17 different pulsotypes, most of which single.

Inducible Expression of both ermB and ermT Conferred High Macrolide Resistance in Streptococcus gallolyticus subsp. pasteurianus Isolates in China

Streptococcus gallolyticus subsp. pasteurianus is an under-recognized pathogen and zoonotic agent causing opportunistic infections in humans. Despite increasing recognition of this subspecies as a cause for human infectious diseases, limited information is known about its antibiotic resistance mechanism. In this study, we aim to identify the molecular mechanism underlying the high macrolide resistance of six S. gallolyticus subsp. pasteurianus isolates from dead ducklings collected in several natural outbreaks in China during 2010–2013. All isolates exhibited multi-drug resistance including high macrolide resistance (MIC ≥ 1024 mg/L for erythromycin, and 512 mg/L for clarithromycin). Efflux-encoding mefA and mefE genes were not detectable in these isolates. The presence of 23S rRNA mutations in specific isolates did not significantly change macrolide MICs. No nucleotide substitutions were found in genes encoding ribosomal proteins L4 or L22. The ermB and ermT genes were found in the genomes of all isolates. These two genes were acquired independently in one highly virulent isolate AL101002, and clustered with Tn916 and IS1216, respectively. The expression of both ermB and ermT in all isolates was erythromycin inducible and yielded comparable macrolide MICs in all six isolates. Taken together, inducible expression of both ermB and ermT conferred high macrolide resistance in these S. gallolyticus subsp. pasterianus isolates. Our findings reveal new macrolide resistance features in S. gallolyticus subsp. pasteurianus by both ermB and ermT.

Bacteremia with the bovis group streptococci: species identification and association with infective endocarditis and with gastrointestinal disease

DNA sequencing of the intergenic spacer (ITS) region was used to identify 53 blood culture isolates that had previously been designated to the bovis group streptococci and clinical data was collected retrospectively from patients' records using a standardized protocol. ITS sequencing identified 19 (35.8%) isolates as Streptococcus gallolyticus subsp. gallolyticus, 12 (22.6%) as S. gallolyticus subsp. pasteurianus, two (3.8%) as S. gallolyticus subsp. macedonicus, seven (13.2%) as S. infantarius subsp. infantarius, 12 (22.6%) as S. lutetiensis and one (1.9%) as S. equinus. The association of S. gallolyticus subsp. gallolyticus with colorectal neoplasia and with infective endocarditis and the association between S. gallolyticus subsp. pasteurianus and pancreatic cancer were found to be clinically important. Also, a very high 1-year mortality rate with S. lutetiensis (66.7%) and S. gallolyticus subsp. pasteurianus (58.7%) bacteremia calls for intensive investigation for underlying disease focusing on the pancreas and the hepatobiliary system.

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.

Genomics, evolution, and molecular epidemiology of the Streptococcus bovis/Streptococcus equinus complex (SBSEC)

The Streptococcus bovis/Streptococcus equinus complex (SBSEC) is a group of human and animal derived streptococci that are commensals (rumen and gastrointestinal tract), opportunistic pathogens or food fermentation associates. The classification of SBSEC has undergone massive changes and currently comprises 7 (sub)species grouped into four branches based on sequences identities: the Streptococcus gallolyticus, the Streptococcus equinus, the Streptococcus infantarius and the Streptococcus alactolyticus branch. In animals, SBSEC are causative agents for ruminal acidosis, potentially laminitis and infective endocarditis (IE). In humans, a strong association was established between bacteraemia, IE and colorectal cancer. Especially the SBSEC-species S. gallolyticus subsp. gallolyticus is an emerging pathogen for IE and prosthetic joint infections. S. gallolyticus subsp. pasteurianus and the S. infantarius branch are further associated with biliary and urinary tract infections. Knowledge on pathogenic mechanisms is so far limited to colonization factors such as pili and biofilm formation. Certain strain variants of S. gallolyticus subsp. macedonicus and S. infantarius subsp. infantarius are associated with traditional dairy and plant-based food fermentations and display traits suggesting safety. However, due to their close relationship to virulent strains, their use in food fermentation has to be critically assessed. Additionally, implementing accurate and up-to-date taxonomy is critical to enable appropriate treatment of patients and risk assessment of species and strains via recently developed multilocus sequence typing schemes to enable comparative global epidemiology. Comparative genomics revealed that SBSEC strains harbour genomics islands (GI) that seem acquired from other streptococci by horizontal gene transfer. In case of virulent strains these GI frequently encode putative virulence factors, in strains from food fermentation the GI encode functions that are pivotal for strain performance during fermentation. Comparative genomics is a powerful tool to identify acquired pathogenic functions, but there is still an urgent need for more physiological and epidemiological data to understand SBSEC-specific traits.