Infective endocarditis (IE) is a life-threatening condition often associated with various complications. A unique subset of IE cases involves the Streptococcus gallolyticus group, which has a well-documented but sometimes poorly understood association with colonic neoplasms. Specifically, colon cancer has a well-established association with IE caused by S. gallolyticus subspecies (spp.) gallolyticus. However, finding colon cancer in cases of IE due to S. gallolyticus spp. pasteurianus is rather unexpected. Herein, we present a rare instance of IE caused by S. gallolyticus spp. pasteurianus in a 62-year-old male, which led to the discovery of an underlying colorectal carcinoma. Considering the overall elevated risk of colon cancer in patients with endocarditis and in patients with S. bovis/S. equinus complex (SBSEC) bacteremia, we decided to proceed to colonoscopy, which revealed adenocarcinoma. The patient was administered a targeted antibiotic regimen and underwent a successful surgical resection, followed by valve replacement surgery. The outcome of this case supports the recommendation of routine colonoscopic evaluation in patients diagnosed with S. gallolyticus bacteremia, including those with subspecies pasteurianus, particularly when there are other associated findings. It strengthens the argument for conducting a colonoscopy in individuals diagnosed with SBSEC endocarditis, while carefully considering the specifics of each clinical situation. Our report highlights the need for heightened clinical vigilance and an integrated approach to treatment in similar cases.

Streptococcus pasteurianus is a zoonotic pathogen causing meningitis and bacteremia in animals and humans. A lack of accurate and convenient detection methods hinders preventing and controlling diseases caused by S. pasteurianus. Additionally, there is limited knowledge about its pathogenicity and antimicrobial resistance characteristics, as there are only three complete genome sequences available. In this study, we established a multiplex PCR assay for the detection of S. pasteurianus, which was applied to six fecal samples from cattle with diarrhea and 285 samples from healthy pigs. Out of the samples tested, 24 were positive, including 5 from pig tonsils, 18 from pig hilar lymph nodes, and 1 from cattle feces. Two strains were isolated from positive samples, and their complete genomes were sequenced. The two strains were non-virulent in mice and multidrug-resistant by the antimicrobial susceptibility test. We first found the presence of genes tet(O/W/32/O) and lsa(E) in S. pasteurianus, leading to resistance to lincosamides and tetracyclines. The convenient and specific multiplex PCR assay provides essential technical support for epidemiological research, and the complete genome sequence of two non-virulent strains contributes to understanding this zoonotic bacterium\'s genomic characteristics and pathogenesis.

The diagnosis of infective endocarditis is challenging because it has a variable clinical presentation and nonspecific symptoms and can present in different forms, especially when an unusual etiological agent is involved. We present the case of a female in her 70s admitted to the hospital with a medical history of bicytopenia, severe aortic stenosis, and rheumatoid arthritis. She had several consultations during which she presented with asthenia and general malaise. A septic screen test was performed that would determine that Streptococcus pasteurianus was present in a blood culture (BC), which was not valued. About three months later, she was hospitalized. In the first 24 hours of admission, the septic screen test was repeated and Streptococcus pasteurianus was isolated in BC. Splenic infarctions and transthoracic echocardiography suggested probable endocarditis, which was confirmed with transesophageal echocardiography. She underwent surgical intervention to remove the perivalvular abscess and replace the aortic prosthesis.

Streptococcus gallolyticus is an uncommon cause of neonatal infections. We describe the first case of fulminant lethal neonatal sepsis due to S. gallolyticus reported in literature. Our patient was an extremely low birth weight premature infant born to a mother with prolonged rupture of amniotic membranes and chorioamnionitis. We also review the cases of neonatal S. gallolyticus infections reported in literature. Fifty-eight percent neonatal S. gallolyticus infections presented in the first week of life. Importantly, S. gallolyticus meningitis is more commonly reported with early-onset infections compared with group B streptococcal meningitis, which is more common with late-onset infections. Streptococcus gallolyticus should be included in differential for neonatal sepsis, particularly in the presence of meningitis in the first week of life. Most cases are sensitive to penicillin; however, cases of reduced sensitivity to penicillin have also been reported.

Streptococcus pasteurianus, an underreported opportunistic pathogen, is considered an increasingly recognized cause of meningitis and bacteremia in many animals and humans worldwide. However, except for some epidemiological studies, there is no report about the gene-deletion mutagenesis, virulence factors, reservoir niches or animal infection models for this pathogen. In this study, we first isolated an S. pasteurianus strain from a newly weaned piglet\'s brain with meningitis. The genomic sequence of this swine isolate WUSP067 shared high homology with that of two human strains. The comparative genome analysis showed that strain WUSP067 contained a fucose utilization cluster absent in human strains, and it shared 91% identity with that of an integrative and conjugative element (ICE) ICEssuZJ20091101-2 from Streptococcus suis, another important swine bacterial pathogen. Strain WUSP067 was resistant to erythromycin, tulathromycin, lincomycin, clindamycin, doxycycline and gentamycin, and ICEs are vehicles for harbouring antimicrobial resistance genes. The infection model was established using the 3-week-old newly weaned ICR mice. The 50% lethal dose value of strain WUSP067 was 4.0 × 107 colony-forming units per mouse. The infected mice showed severe signs of meningitis and pathological changes in brains. Furthermore, the capsule-deficient mutant was generated using natural transformation, and we showed that capsule was an essential virulence factor for S. pasteurianus. In addition, we found that tonsils and hilar lymph nodes of healthy pigs may be reservoir niches for this bacterium. Thus, our study provided valuable information about the pathogenetic characteristics and antimicrobial resistance of S. pasteurianus and paved the way for studying its pathogenesis.

Streptococcus pasteurianus is a rare cause of neonatal infection, with only 3 cases reported in the USA and 18 cases reported in other countries within the past decade. Neonatal S. pasteurianus infection typically presents as meningitis. This case report describes the first neonatal case of S. pasteurianus endocarditis in the literature, in addition to a neonatal case of S. pasteurianus infection presenting as pneumonitis without meningitis. The S. pasteurianus infections in these two cases are unusual not only because of how rare this particular pathogen is, but also because of the atypical clinical manifestations.
The first patient is a full-term male infant admitted to NICU at 20 h of life due to respiratory distress. He was empirically started on ampicillin and gentamicin for presumed sepsis. Laboratory analysis of cerebral spinal fluid obtained after initiation of antibiotics was suggestive of partially treated meningitis. Blood cultures came back positive for S. pasteurianus. The neonate was transitioned from ampicillin to cefepime, while gentamicin was continued. Echocardiograph showed a possible tricuspid valve vegetation concerning for endocarditis. Due to the unusual complication of endocarditis, the patient remained on IV cefepime for 28 days rather than the more conventional duration of 14-21 days reported in the literature. The baby clinically improved with no evidence of thrombi or vegetations on repeat cardiac echo. The second patient is a full-term male infant who required intubation at birth for respiratory distress. Chest X-ray findings were concerning for meconium aspiration with pneumonitis. The baby went into septic shock and was empirically started on ampicillin and gentamicin. Blood cultures came back positive for S. pasteurianus, while cerebral spinal fluid and urine cultures were negative. Ampicillin and gentamicin were discontinued after 3 days and the baby was started on cefepime and clindamycin for a total 14-day course. The baby clinically recovered and was discharged from NICU without any sequelae.
These two cases highlight the importance of recognizing S. pasteurianus as a potential cause of neonatal sepsis and the importance of recognizing endocarditis and pneumonitis as possible clinical manifestations of this infection.

A previous study demonstrated that a highly virulent strain of Streptococcus gallolyticus subsp. pasteurianus, designated as the AL101002 strain, induced high mortality in ducklings with splenic lesions. In this study, 42 ducklings were subcutaneously inoculated with the AL101002 strain to study changes in splenic lesions over time. The spleens from these ducklings were significantly enlarged by congestion and edema, and/or showed multiple marbled areas 14 days postinoculation (dpi). The AL101002 strain was reisolated from the spleens and blood and confirmed by immunohistochemistry (IHC) with the use of anti-AL101002 antibody. Histopathologically, the main lesion was macrophage necrosis in the spleens from 1 to 7 dpi. Terminal dUTP nick-end labeling assay, transmission electron microscopy, and IHC by anti-macrosialin antibody (CD68) demonstrated that macrophage necrosis was necroptosis, which was further confirmed by quantitative (real-time) reverse-transcriptase PCR analysis. Two major factors of apoptosis, caspase 3 and caspase 8, did not significantly change during the AL101002 infection, suggesting that apoptosis signals were not activated. However, the key factor mixed lineage kinase like was increased significantly (P < 0.05) from Day 1 to Day 14 dpi. Inflammatory cytokine interleukin-1β and interleukin-6 had significantly (P < 0.01) upregulated expression in the spleens on Day 1 dpi. Tumor necrosis factor α was downregulated from Day 1 to Day 5 dpi, but increased from Day 7 to Day 14. Our results demonstrated that AL101002 strain mainly infects macrophages and resulted in macrophage necroptosis and suggested that macrophage necroptosis in spleens is involved in the pathogenesis of S. gallolyticus subsp. pasteurianus infection in ducklings.

Apnea, cyanosis, lethargy and prolongation in capillary filling time developed on the postnatal 37(th) day in a preterm baby who was born at the 30(th) gestational week with a birth weight of 1 300 g. Acute phase reactants and immature/total neutrophil count ratio were found to be high. The patient who was diagnosed with sepsis was successfully treated with meropenem which was started empirically. In his blood culture Streptococcus pasteurianus grew. S. pasteurianus is in the subgroup of streptococcus bovis which is one of the D group streptococci and its previous name is S. bovis type II/2. In the literature, there are very few cases of neonatal infection related with this bacterium. As far as we know, this is first case of neonatal sepsis caused by S. pasteurianus in Turkey. In addition, we tried to determine the clinical properties of neonatal infections arising from S. pasteurianus by reviewing the literature.

Streptococcus bovis is a well-known cause of endocarditis, but its role in other infections has not been well described. We analysed prospectively all patients with biliary tract infections caused by S. bovis group during the period 1988-2011. We selected those cases associated with cholangitis and cholecystitis, defined according to Tokyo guidelines. Identification of the strains was performed using the API 20 Strep and the GP card of the Vitek 2 system, and was confirmed by molecular methods. Our series included 51 cases (30 cholangitis and 21 cholecystitis). The associated microorganisms were: Streptococcus infantarius (biotype II/1) 29 cases (57%), Streptococcus gallolyticus subsp. pasteurianus (biotype II/2) 20 cases (39%) and Streptococcus gallolyticus subsp. gallolyticus (biotype I) two cases (4%). The only difference found between S. infantarius and S. gallolyticus subsp. pasteurianus was a greater association of the first with malignant strictures of the bile ducts: 48% (14/29) versus 5% (1/20), p <0.001. Thirty-seven of the cases also had bacteraemia, causing 20% (37/185) of all S. bovis bacteraemia, with differences between S. gallolyticus subsp. gallolyticus (2/112; 2%) and the other two microorganisms: S. infantarius and S. gallolyticus subsp. pasteurianus (35/73; 48%; p <0.001). The vast majority of biliary tract infections due to S. bovis group are caused by S. infantarius and S. gallolyticus subsp. pasteurianus (S. bovis biotype II), and nearly half of the bacteraemia due to these two species has a biliary source (43% of the S. infantarius and 56% of S. gallolyticus subsp. pasteurianus).