Case report: brain and liver abscesses caused by oral infection with Streptococcus intermedius

Focal Neurological Symptoms at Initial Presentation Could Be a Potential Risk Factor for Poor Prognosis Among Patients With Multiple Brain Abscesses by Streptococcus anginosus Group: A Case Report With Literature Review

Streptococcus anginosus group (SAG) is one of the most common microbes of brain abscesses. Brain abscesses caused by SAG have often delayed diagnosis since both blood and cerebrospinal fluid cultures are negative in half of the cases. A 68-year-old man developed persistent fever, headache, and myalgias for two weeks and visited our department. He was treated with oral antibiotics without laboratory work. Although examination showed no focal neurological symptoms, a careful interview revealed a history of unusual behavior for a few minutes on the previous day. Whole body contrast-enhanced computed tomography (CT) and head magnetic resonance imaging (MRI) showed two ring enhancements close to the bilateral ventricles, which were consistent with a diagnosis of the brain abscesses. An emergent surgical puncture for the larger abscess with intravenous antimicrobial therapy quickly improved his condition, and he was discharged on day 36 with no sequelae. We retrospectively reviewed works of literature on cases with multiple brain abscesses by SAG to assess potential prognostic factors for neurological sequelae. Statistical analyses of 12 cases, including 11 cases from the literature review and the current case, were performed between groups with or without poor prognosis. Among potential risk factors of age, sex, focal neurological symptoms, duration from onset to treatment, abscess formation of other organs, presence of surgical drainage, and positive for blood culture, only focal neurological symptoms at the initial presentation were significantly associated with poor prognosis (no poor prognosis, 1/4 cases vs poor prognosis group, 8/8 cases; p=0.01). Careful interviews and detailed examinations should be conducted to assess the possibility of brain abscesses among patients with fever of unknown etiology. Otherwise, a delayed diagnosis might result in poor prognoses such as death or neurological sequelae due to this disease's nature, which has few specific symptoms in the early stages.

The Clinical View on Streptococcus anginosus Group – Opportunistic Pathogens Coming Out of Hiding

Three distinct streptococcal species: Streptococcus anginosus, Streptococcus intermedius, and Streptococcus constellatus, belonging to the Streptococcus anginosus group (SAG), also known as Streptococcus milleri group, have been attracting clinicians and microbiologists, not only as oral commensals but also as opportunistic pathogens. For years they have been simply classified as so called viridans streptococci, and distinct species were not associated with particular clinical manifestations. Therefore, description of SAG members are clearly underrepresented in the literature, compared to other medically relevant streptococci. However, the increasing number of reports of life-threatening infections caused by SAG indicates their emerging pathogenicity. The improved clinical data generated with the application of modern molecular diagnostic techniques allow for precise identification of individual species belonging to SAG. This review summarizes clinical reports on SAG infections and systematizes data on the occurrence of individual species at the site of infection. We also discuss the issue of proper microbiological diagnostics, which is crucial for further clinical treatment.

Brain Abscess: A Rare Clinical Case with Oral Etiology

Brain abscess is a very rare condition but has a significant mortality rate. The three main routes of inoculation are trauma, contiguous focus, and the hematogenous route. The odontogenic focus is infrequent and is usually a diagnosis of exclusion. This paper presents a brain abscess case proven to be of dental origin, caused by Actinomyces meyeri and Fusobacterium nucleatum. This case highlights the risk underlying untreated dental disease and why oral infectious foci removal and good oral health are essential in primary care.

Concomitant Liver and Brain Abscesses Caused by Parvimonas Micra

Anaerobic infections have been reported to be responsible for 3-10% of pyogenic liver abscesses in Korea, and reported anaerobes include Fusobacterium, Bacillus fragilis, and Bacteroides melaninogenicus. Parvimonas micra is an anaerobic, Gram-positive, non-spore-forming bacterial species and a constituent of normal flora on skin, vagina, gastrointestinal tract, and oral cavity that can cause opportunistic infections. However, it has only rarely been reported to be a cause of liver abscess; only one such case has been reported in Korea. We experienced a case of concomitant liver and brain abscesses caused by Parvimonas micra in a non-immunodeficient 65-year-old female patient without diabetes or periodontal disease. Parvimonas micra infection was confirmed by blood culture using VITEK^® 2 cards and by bacterial 16s ribosomal RNA gene sequencing. We conclude that we should not overlook anaerobes as a cause of liver abscess.

Streptococcus periodonticum sp. nov., Isolated from Human Subgingival Dental Plaque of Periodontitis Lesion

A novel facultative anaerobic and Gram-stain-positive coccus, designated strain ChDC F135^T, was isolated from human subgingival dental plaque of periodontitis lesion and was characterized by polyphasic taxonomic analysis. The 16S rRNA gene (16S rDNA) sequence of strain ChDC F135^T was closest to that of Streptococcus sinensis HKU4^T (98.2%), followed by Streptococcus intermedia SK54^T (97.0%), Streptococcus constellatus NCTC11325^T (96.0%), and Streptococcus anginosus NCTC 10713^T (95.7%). In contrast, phylogenetic analysis based on the superoxide dismutase gene (sodA) and the RNA polymerase beta-subunit gene (rpoB) showed that the nucleotide sequence similarities of strain ChDC F135^T were highly similar to the corresponding genes of S. anginosus NCTC 10713^T (99.2% and 97.6%, respectively), S. constellatus NCTC11325^T (87.8% and 91.4%, respectively), and S. intermedia SK54^T (85.8% and 91.2%, respectively) rather than those of S. sinensis HKU4^T (80.5% and 82.6%). The complete genome of strain ChDC F135^T consisted of 1,901,251 bp and the G+C content was 38.9 mol %. Average nucleotide identity value between strain ChDC F135^T and S. sinensis HKU4^T or S. anginosus NCTC 10713^T were 75.7% and 95.6%, respectively. The C_14:0 composition of the cellular fatty acids of strain ChDC F135^T (32.8%) was different from that of S. intermedia (6-8%), S. constellatus (6-13%), and S. anginosus (13-20%). Based on the results of phylogenetic and phenotypic analysis, strain ChDC F135^T (= KCOM 2412^T = JCM 33300^T) was classified as a type strain of a novel species of the genus Streptococcus, for which we proposed the name Streptococcus periodonticum sp. nov.

Antibiotic Prophylaxis for Dental Treatment in Patients with Immunodeficiency

Routine antibacterial prophylaxis is recommended before dental procedures in select patient populations. Currently, no guidelines are in place for routine prophylaxis before dental procedures in patients with primary immunodeficiency diseases. We review risk factors and provide recommendations on routine dental care and antibacterial prophylaxis in patients with primary immunodeficiency diseases.

An unusual case of dental infection by Pseudomonas aeruginosa causing a brain abscess: case report

A brain abscess may result when dental infection reaches the brain through contiguous anatomic cavities such as the maxillary sinus, the ethmoid sinus and the orbital cavity. It is an important complication and should be treated aggressively. Such treatment would include the excision of the etiological factor, drainage and adjuvant antibiotic therapy. The present case concerns a 23 year old woman who presented at the General Hospital of Nova Iguaçu with complaints of pain in the right side of the face and was diagnosed with acute sinusitis. Antibiotics and analgesics were prescribed to treat the disease. However, after 10 days, she returned to the emergency room, presenting with proptosis of the right eyeball, subconjunctival haemorrhage, ophthalmoplegia and intense pain in the right orbit, in addition to headaches. After computed tomography was performed, she was diagnosed with a brain abscess in the frontal lobe with the involvement of the maxillary right first molar, the maxillary sinus, the ethmoid sinus and the orbital cavity. With culturing of the secretion, the growth of Pseudomonas aeruginosa colonies was evident. Treatment consisted of a craniotomy to drain the brain abscess, a Caldwell-Luc procedure to drain the right maxillary sinus, dental extraction and aggressive antibiotic therapy. After 6 weeks, the patient was discharged with no neurological sequelae.

The oral cavity microbiota: between health, oral disease, and cancers of the aerodigestive tract

Many studies show that the human microbiome plays a critical role in the chronic pathologies of obesity, inflammatory bowel diseases, and diabetes. More recently, the interaction between cancer and the microbiome has been highlighted. Most studies have focused on the gut microbiota because it represents the most extensive bacterial community, and the body of evidence correlating it with gut syndromes is increasing. However, in the strict sense, the gastrointestinal (GI) tract begins in the oral cavity, and special attention should be paid to the specific flora of this cavity. This study reviewed the current knowledge about the various microbial ecosystems of the upper part of the GI tract and discussed their potential link to carcinogenesis. The overall composition of the microbial communities, as well as the presence or absence of "key species", in relation to carcinogenesis is addressed. Alterations in the oral microbiota can potentially be used to predict the risk of cancer. Molecular advances and the further monitoring of the microbiota will increase our understanding of the role of the microbiota in carcinogenesis and open new perspectives for future therapeutic and prophylactic modalities.

Bacteraemia before, during and after tooth extraction in horses in the absence of antimicrobial administration

BACKGROUND

Transient bacteraemia can occur during tooth extraction in humans, and dogs and can lead to severe infectious sequelae. Several case reports describe distant site infections following equine tooth extraction, but the occurrence of bacteraemia during dental surgery has not been evaluated in the horse.

OBJECTIVES

To determine if transient bacteraemia occurs during tooth extraction in horses, describe isolated organisms and compare these with those found in the diseased teeth.

STUDY DESIGN

Prospective, observational study.

METHODS

Blood was collected aseptically for blood culture before, during and after oral extraction of incisor, canine or cheek teeth from 20 adult horses undergoing dental extraction that had not received antimicrobial agents for at least 4 weeks prior to surgery. Bacteria found in blood cultures were compared with those found in swab samples obtained from the extracted teeth.

RESULTS

Eighteen of 20 horses had positive blood cultures at one or more time points. Streptococcus spp., Actinomyces spp., Fusobacterium spp. and Prevotella spp. were most commonly found. Bacterial genera isolated from swab samples of extracted teeth largely corresponded with those identified in blood cultures.

MAIN LIMITATIONS

This study was limited by its use of only conventional bacterial culture, the lack of statistical analysis to explore associations between gingiva score and the occurrence of bacteraemia, and the lack of an age-matched control group of horses not undergoing exodontia.

CONCLUSIONS

Transient bacteraemia of oral origin commonly occurs during dental extraction in horses. As none of the horses developed complications associated with bacteraemia during the observation period after surgery, the significance of this bacteraemia remains uncertain. The Summary is available in Chinese - see Supporting Information.

Intra-Abdominal Abscess and Primary Peritonitis Caused by Streptococcus anginosus

Introduction

The Streptococcus anginosus group of bacteria are low-virulence bacteria existing as commensals in the oral flora and gastrointestinal tracts of humans. S. anginosus may spread to the blood in individuals with poor oral hygiene in cases of oral infections, such as gingivitis and tooth abscesses, that develop following the loss of mucosal unity. This may lead to infections in the whole body, primarily as brain and liver abscesses.

Case Presentation

A 32-year-old male patient presented with complaints of nausea, vomiting, and diffuse abdominal pain. Diffuse abdominal tenderness and rebound tenderness were detected particularly in the epigastrium and right upper quadrant. Laboratory assessment revealed a leukocyte count of 20,500/mm³. Free fluid around the liver and heterogeneous areas of abscess formation in the right lateral gallbladder were revealed on abdominal computed tomography. Diffuse adhesions between the bowel and seropurulent free liquid in the abdomen were detected on surgical exploration, and a sample was taken for cultures. The patient was discharged without complications on the sixth postoperative day and his antibiotic course was completed with 4 weeks of oral treatment. We reviewed the literature for similar cases of disseminated pyogenic infections caused by the S. anginosus group.

Conclusions

It should be kept in mind that the oral flora bacterium S. anginosus may cause transient bacteremia and deep-seated organ abscesses in immunodeficient patients with poor oral hygiene. Such patients with intra-abdominal abscesses should be treated with antibiotics and surgery.

Antibiotic susceptibility of periodontal Streptococcus constellatus and Streptococcus intermedius clinical isolates

BACKGROUND

Streptococcus constellatus and Streptococcus intermedius in subgingival dental plaque biofilms may contribute to forms of periodontitis that resist treatment with conventional mechanical root debridement/surgical procedures and may additionally participate in some extraoral infections. Because systemic antibiotics are often used in these clinical situations, and little is known of the antibiotic susceptibility of subgingival isolates of these two bacterial species, this study determined the in vitro susceptibility to six antibiotics of fresh S. constellatus and S. intermedius clinical isolates from human periodontitis lesions.

METHODS

A total of 33 S. constellatus and 17 S. intermedius subgingival strains, each recovered from separate patients with severe chronic periodontitis (n = 50) before treatment, were subjected to antibiotic gradient strip susceptibility testing with amoxicillin, azithromycin, clindamycin, ciprofloxacin, and doxycycline on blood-supplemented Mueller-Hinton agar and to the inhibitory effects of metronidazole at 16 mg/L in an enriched Brucella blood agar dilution assay. Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing interpretative standards were used to assess the results.

RESULTS

Clindamycin was the most active antibiotic against S. constellatus (minimum inhibitory concentration at 90% [MIC90] 0.25 mg/L), and amoxicillin was most active against S. intermedius (MIC90 0.125 mg/L). A total of 30% of the S. constellatus and S. intermedius clinical isolates were resistant in vitro to doxycycline, 98% were only intermediate in susceptibility to ciprofloxacin, and 90% were resistant to metronidazole at 16 mg/L.

CONCLUSION

Subgingival S. constellatus and S. intermedius exhibited variable antibiotic susceptibility profiles, potentially complicating empirical selection of periodontitis antibiotic therapy in patients who are species positive.

Association between periodontal disease and septicemia due to pyogenic hepatic abscess

Case of a 65 year-old man with type-2 diabetes mellitus for<br />15 years who complained of abdominal pain in the right upper<br />quadrant associated with unquantified fever and weight loss<br />over a period of 25 days. In the emergency room, he presented<br />tachycardia, tachypnea and fever of 37 º C, diffuse abdominal<br />pain from light palpation without peritoneal irritation or<br />right upper quadrant tenderness upon fist percussion test.<br />Within a few hours the patient evolved to septic shock and<br />required transfer to the intermediate care unit. The abdominal<br />computerized axial tomography showed multiloculated<br />hepatic abscess. Percutaneous drainage was performed with<br />the culture positive for Escherichia coli and Fusobacterium<br />spp. Then, the differential diagnosis was made between<br />pyogenic or amebic liver abscess. Subsequently, oral cavity<br />examination revealed severe periodontal disease with coronal<br />destruction; therefore, extraction was scheduled.

Streptococcus intermedius Bacteremia and Liver Abscess following a Routine Dental Cleaning

Streptococcus intermedius is a member of the Streptococcus anginosus group of bacteria. This group is part of the normal flora of the oropharynx, genitourinary, and gastrointestinal tracts; however, they have been known to cause a variety of purulent infections including meningitis, endocarditis, and abscesses, even in immunocompetent hosts. In particular, S. intermedius has been associated with the development of liver and brain abscesses. There have been several case reports of S. intermedius liver abscesses with active periodontal infection. To our knowledge, however, there has not been a case following a routine dental procedure. In fact, the development of liver abscesses secondary to dental procedures is very rare in general, and there are only a few case reports in the literature describing this in relation to any pathogen. We present a rare case of S. intermedius bacteremia and liver abscess following a dental cleaning. This case serves to further emphasize that even routine dental procedures can place a patient at risk of the development of bacteremia and liver abscesses. For this reason, the clinician must be sure to perform a detailed history and careful examination. Timely diagnosis of pyogenic liver abscesses is vital, as they are typically fatal if left untreated.

Multiple brain abscesses in an immunocompetent patient after undergoing professional tooth cleaning

BACKGROUND

Dental disorders and dental treatment are among the variety of causes of brain abscess.

CASE DESCRIPTION

The authors present the case of a patient who developed multiple brain abscesses after undergoing professional tooth cleaning. The results of a diagnostic work-up ruled out an underlying immunodeficiency. After receiving neurosurgical intervention and intensive care treatment by means of local and intravenous antibiotics for 24 days, the patient was transferred to another hospital for rehabilitation. Six months after the treatment, the patient still had moderate residual paresis of the left leg.

PRACTICAL IMPLICATIONS

Although it happens rarely, professional tooth cleaning may be considered a cause of brain abscesses even in otherwise healthy patients.

Effects of extracellular DNA and DNA-binding protein on the development of a Streptococcus intermedius biofilm

AIMS

The aim of this study was to clarify the effects of homologous and heterologous extracellular DNAs (eDNAs) and histone-like DNA-binding protein (HLP) on Streptococcus intermedius biofilm development and rigidity.

METHODS AND RESULTS

Formed biofilm mass was measured with 0·1% crystal violet staining method and observed with a scanning electron microscope. The localizations of eDNA and extracellular HLP (eHLP) in formed biofilm were detected by staining with 7-hydoxyl-9H-(1,3-dichloro-9,9-dimethylacridin-2-one) and anti-HLP antibody without fixation, respectively. DNase I treatment (200 U ml(-1)) markedly decreased biofilm formation and cell density in biofilms. Colocalization of eHLP and eDNA in biofilm was confirmed. The addition of eDNA (up to 1 μg ml(-1)) purified from Strep. intermedius, other Gram-positive bacteria, Gram-negative bacteria, or human KB cells into the Strep. intermedius culture increased the biofilm mass of all tested strains of Strep. intermedius, wild-type, HLP-downregulated strain and control strains. In contrast, the addition of eDNA (>1 μg ml(-1)) decreased the biofilm mass of all Strep. intermedius strains.

CONCLUSIONS

These findings demonstrated that eDNA and eHLP play crucial roles in biofilm development and its rigidity.

SIGNIFICANCE AND IMPACT OF THE STUDY

eDNA- and HLP-targeting strategies may be applicable to novel treatments for bacterial biofilm-related infectious diseases.

Liver abscess after implantation of dental prosthesis

Pyogenic liver abscesses are rare but a life-threatening important condition. Dental procedures constitute only rare cases of pyogenic liver abscesses, with only a few cases in the literature. We report a patient with liver abscess following a dental procedure. A 74 years old diabetic male patient was admitted to our hospital with complaints of fatigue, 40 °C fever, rigors and right upper quadrant pain, 3-4 d after a dental procedure. Physical examination revealed fever and tenderness in the right upper quadrant. Laboratory examination revealed leucocytosis, elevated erythrocyte sedimentation rate and C-reactive protein and moderately elevated transaminases. An abscess was detected in radiological examination in the medial part of the left lobe of liver, neighboring the gall bladder. He was successfully treated with percutaneous abscess drainage and antibiotherapy.

Liver abscess caused by periodontal bacterial infection with Fusobacterium necrophorum

Liver abscess is recognized as a life-threatening disease. However, even in recent years, approximately 50% of liver abscess cases are considered to be cryptogenic. Here, we report a case of liver abscess associated with periodontal bacterial infection by Fusobacterium necrophorum, which is commonly found in the oropharyngeal flora. A 36-year-old man presented with fever and contrast-enhanced abdominal computed tomography revealed multiple liver abscesses. F.necrophorum was isolated from oral smears, liver aspirates and blood samples. Liver abscesses caused by periodontal bacterial infection are rare, however, the incidence is expected to increase in the future, as periodontitis is extremely common and is on the rise as one of the most common chronic infections in the world. A systemic survey including periodontitis may be required for the exact diagnosis of the source of infection.

Invasion of human aortic endothelial cells by oral viridans group streptococci and induction of inflammatory cytokine production

Oral viridans group streptococci are the major commensal bacteria of the supragingival oral biofilm and have been detected in human atheromatous plaque. Atherosclerosis involves an ongoing inflammatory response, reportedly involving chronic infection caused by multiple pathogens. The aim of this study was to examine the invasion of human aortic endothelial cells (HAECs) by oral viridans group streptococci and the subsequent cytokine production by viable invaded HAECs. The invasion of HAECs by bacteria was examined using antibiotic protection assays and was visualized by confocal scanning laser microscopy. The inhibitory effects of catalase and cytochalasin D on the invasion of HAECs were also examined. The production of cytokines by invaded or infected HAECs was determined using enzyme-linked immunosorbent assays, and a real-time polymerase chain reaction method was used to evaluate the expression of cytokine messenger RNA. The oral streptococci tested were capable of invading HAECs. The number of invasive bacteria increased with the length of the co-culture period. After a certain co-culture period, some organisms were cytotoxic to the HAECs. Catalase and cytochalasin D inhibited the invasion of HAECs by the organism. HAECs invaded by Streptococcus mutans Xc, Streptococcus gordonii DL1 (Challis), Streptococcus gordonii ATCC 10558 and Streptococcus salivarius ATCC 13419 produced more cytokine(s) (interleukin-6, interleukin-8, monocyte chemoattractant protein-1) than non-invaded HAECs. The HAECs invaded by S. mutans Xc produced the largest amounts of cytokines, and the messenger RNA expression of cytokines by invaded HAECs increased markedly compared with that by non-invaded HAECs. These results suggest that oral streptococci may participate in the pathogenesis of atherosclerosis.

Intermedilysin induces EGR-1 expression through calcineurin/NFAT pathway in human cholangiocellular carcinoma cells

Intermedilysin (ILY) is a cholesterol-dependent cytolysin produced by Streptococcus intermedius, which is associated with human brain and liver abscesses. Although intrahepatic bile duct cells play a valuable role in the pathogenesis of liver abscess, the molecular mechanism of ILY-treated intrahepatic bile duct cells remains unknown. In this study, we report that ILY induced a nuclear accumulation of intracellular calcium ([Ca(2+)]i) in human cholangiocellular cells HuCCT1. We also demonstrate that 10 ng/ml ILY induced NFAT1 dephosphorylation and its nuclear translocation in HuCCT1 cells. In contrast to the result that ILY induced NF-κB translocation in human hepatic HepG2 cells, ILY did not affect NF-κB localization in HuCCT1 cells. Dephosphorylation and nuclear translocation of NFAT1 caused by ILY were prevented by [Ca(2+)]i calcium chelator, BAPTA/AM, and calcineurin inhibitors, cyclosporine A and tacrolimus. ILY induced early growth response-1 (EGR-1) expression and it was inhibited by the pre-treatment with cyclosporine A, indicating that the calcineurin/NFAT pathway was involved in EGR-1 expression in response to ILY. ILY-induced calcineurin/NFAT1 activation and sequential EGR-1 expression might be related to the pathogenesis of S. intermedius in human bile duct cells.

Systemic endotoxin levels in chronic indolent periodontal infections

BACKGROUND AND OBJECTIVE

Periodontal disease has been linked with an increased risk of various systemic diseases. A plausible biologic explanation for this link includes the opportunity for oral pathogens to translocate to the circulation as a result of breakdown in integrity of the oral epithelium. This study refined a methodology used to detect endotoxin activity in the serum of subjects with indolent periodontal infections.

MATERIAL AND METHODS

The QCL Kinetic Chromogenic Assay (Cambrex) is a kinetic measure of endotoxin activity. Sera from 211 pregnant women with periodontitis enrolled in the Obstetrics and Periodontal Therapy Trial were used to develop the assay further and to evaluate the detection of endotoxin activity that might accompany a low-level bacteremia in chronic periodontitis.

RESULTS

We optimized the system to increase the sensitivity and reproducibility of the assay. The refined system was able to detect endotoxin activity in serum at > 0.0125 EU/mL. At baseline (13-16 wk of gestation), 35.5% of the women were positive for endotoxin activity (1.62 +/- 2.21; range: 0.38-15 EU/mL).

CONCLUSION

This report describes a sensitive measure of endotoxin activity in serum. The procedure allowed us to document levels of this microbial virulence factor in serum of individuals with indolent infections such as periodontal disease.

Microbiology of odontogenic bacteremia: beyond endocarditis

SUMMARY

The human gingival niche is a unique microbial habitat. In this habitat, biofilm organisms exist in harmony, attached to either enamel or cemental surfaces of the tooth as well as to the crevicular epithelium, subjacent to a rich vascular plexus underneath. Due to this extraordinary anatomical juxtaposition, plaque biofilm bacteria have a ready portal of ingress into the systemic circulation in both health and disease. Yet the frequency, magnitude, and etiology of bacteremias due to oral origin and the consequent end organ infections are not clear and have not recently been evaluated. In this comprehensive review, we address the available literature on triggering events, incidence, and diversity of odontogenic bacteremias. The nature of the infective agents and end organ infections (other than endocarditis) is also described, with an emphasis on the challenge of establishing the link between odontogenic infections and related systemic, focal infections.

Streptococcus intermedius causing infective endocarditis and abscesses: a report of three cases and review of the literature

Background

Streptococcus intermedius is a member of the Streptococcus anginosus group. Clinical disease with S. intermedius is characterized by abscess formation and rarely endocarditis. Identification of Streptococcus intermedius is difficult, leading to the development of molecular methods to more accurately identify and characterize this organism.

Case presentation

Over a period of 6 months we encountered three cases of invasive Streptococcus intermedius infection presenting as hepatic abscesses, brain abscess, and endocarditis. We confirmed our microbiologic diagnosis through 16S sequencing and found a common virulence gene in each case.

Conclusion

Our report illustrates three different clinical manifestations due to Streptococcus intermedius infection that can be encountered in healthy individuals in a community hospital setting. To our knowledge, this is the first case of Streptococcus intermedius endocarditis confirmed by 16S sequencing analysis. The use of molecular methods may allow a better understanding of the epidemiology and pathogenesis of this organism.

Splenic abscess in an infant caused by Streptococcus intermedius

We report a 20-month-old girl with splenic abscess. The patient was admitted to our hospital because of persistent high fever and abdominal pain. Laboratory data showed leucocytosis and elevated C-reactive protein levels. Abdominal computed tomography showed multiple low-density lesions in the spleen. These findings were consistent with a diagnosis of splenic abscess. She was successfully treated with ultrasonographically guided percutaneous drainage for 11 days and intravenous antibiotic for 17 days. On culture, aspirated fluid from the abscess grew Streptococcus intermedius. This case illustrates that the differential diagnosis of unknown-focus infection in infants should include splenic abscess. We recommend conservative therapy (antibiotics and drainage) as first-line therapy for splenic abscess in pediatric patients, based on the importance of the immunological functions of the spleen.

Histone-like DNA binding protein of Streptococcus intermedius induces the expression of pro-inflammatory cytokines in human monocytes via activation of ERK1/2 and JNK pathways

Streptococcus intermedius is a commensal associated with serious, deep-seated purulent infections in major organs, such as the brain and liver. Histone-like DNA binding protein (HLP) is an accessory architectural protein in a variety of bacterial cellular processes. In this study, we investigated the mechanisms of pro-inflammatory cytokine inductions in THP-1 cells by stimulation with recombinant HLP of S. intermedius (rSi-HLP). rSi-HLP stimulation-induced production of pro-inflammatory cytokines (IL-8, IL-1 beta and TNF-alpha) occurred in a time- and dose-dependent manner. In contrast with the heat-stable activity of DNA binding, the induction activity of rSi-HLP was heat-unstable. In subsequent studies, rSi-HLP acted cooperatively with lipoteichoic acid, the synthetic Toll-like receptor 2 agonist, Pam3CSK4, and the cytosolic nucleotide binding oligomerization domain 2 receptor agonist, muramyldipeptide. Furthermore, Western blot and blocking assays with specific inhibitors showed that rSi-HLP stimulation induced the activation of cell signal transduction pathways, extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK). In addition to its physiological role in bacterial growth through DNA binding, these results indicate that Si-HLP can trigger a cascade of events that induce pro-inflammatory responses via ERK1/2 and JNK signal pathways, and suggest that bacterial HLP may contribute to the activation of host innate immunity during bacterial infection.