Streptococcus milleri group: renewed interest in an elusive pathogen

Empyema caused by Streptococcus constellatus in a patient infected with HIV: a case report and literature review

BACKGROUND

Empyema caused by Streptococcus constellatus (S. constellatus) is rare in patients with HIV. To analyze the clinical data of a patient living with HIV (PLHIV), who got empyema caused by S. constellatus, investigating the diagnosis and treatment of this disease through literature review to improve the clinical understanding of this disease.

CASE PRESENTATION

We have reported here a 58-year-old male PLHIV with cough, wheezing, and fever for 20 days. He has a history type 2 diabetes, alcohol abuse, and a teeth extracted. Chest computed tomography revealed multiple encapsulated pleural effusions, pneumatosis, and partial compressive atelectasis in the right lung. Submission of pleural efusions timely, and then cultures revealed S. constellatus. After comprehensive treatment, including antibiotics, closed pleural drainage, and intrapleural injection of urokinase, the pleural efusion was absorbed, and chest computed tomography also confirmed the improvement.

CONCLUSIONS

S. constellatus should not be neglected as a pus pathogen in patients with HIV. comprehensive treatment is important for empyema of S. constellatus.

Streptococcus anginosus Empyema Induced by Dental Abscess: A Case Report

Streptococcus anginosus is a gram-positive catalase-negative cocci and commensal flora of the oropharynx and gastrointestinal tract. Streptococcus anginosus is known to be highly virulent and known to cause invasive pyogenic infection which may necessitate emergent surgical treatment. We present a case of a 53-year-old female with dental caries and uncontrolled diabetes mellitus who presented with progressive shortness of breath for 1 week. A computed tomography scan of the chest showed a loculated empyema which was treated with emergent video-assisted thoracoscopic surgery. Pleural fluid culture as well as sputum cultures grew Streptococcus anginosus. The patient was treated intravenous cephalosporins and discharged on oral antibiotics after 14 days with outpatient dental follow-up and improvement of symptoms.

Microbial aetiology of brain abscess in a UK cohort: Prominent role of Streptococcus intermedius

BACKGROUND

Brain abscess is an uncommon condition, but carries high mortality. Current treatment guidelines are based on limited data. Surveillance of clinical, radiological and microbiology data is important to inform patient stratification, interventions, and antimicrobial stewardship.

METHODS

We undertook a retrospective, observational study of patients with brain abscess, based on hospital coding, in a UK tertiary referral teaching hospital. We reviewed imaging data, laboratory microbiology, and antibiotic prescriptions.

RESULTS

Over a 47 month period, we identified 47 adults with bacterial brain abscess (77% male, median age 47 years). Most of the abscesses were solitary frontal or parietal lesions. A microbiological diagnosis was secured in 39/47 (83%) of cases, among which the majority were of the Streptococcus milleri group (27/39; 69%), with a predominance of Streptococcus intermedius (19/27; 70%). Patients received a median of 6 weeks of intravenous antibiotics (most commonly ceftriaxone), with variable oral follow-on regimens. Ten patients (21%) died, up to 146 days after diagnosis. Mortality was significantly associated with increasing age, multiple abscesses, immunosuppression and the presence of an underlying cardiac anomaly.

CONCLUSION

Our data suggest that there has been a shift away from staphylococcal brain abscesses, towards S. intermedius as a dominant pathogen. In our setting, empiric current first line therapy with ceftriaxone remains appropriate on microbiological grounds and narrower spectrum therapy may sometimes be justified. Mortality of this condition remains high among patients with comorbidity. Prospective studies are required to inform optimum dose, route and duration of antimicrobial therapy.

Invasive pyogenic infection and infective endocarditis due to Streptococcus anginosus: A case report

RATIONALE

Streptococcus anginosus mostly colonizes the digestive and genitourinary system, including the oropharyngeal region. It commonly causes invasive pyogenic infection, but less likely causes infective endocarditis (IE).

PATIENT CONCERNS

An 18-year-old woman who had an underlying mitral valve prolapse without mitral regurgitation presented to our hospital with low-grade fever, left leg weakness, and left abdominal pain. She was diagnosed with brain infarction and microabscess as well as IE. The patient totally recovered after the 6-week course of intravenous antibiotics.

DIAGNOSIS

Brain magnetic resonance imaging revealed brain infarction and microabscess. Abdominal computed tomography revealed splenic and left renal infarction. Three sets of blood culture were positive for S anginosus. Transthoracic echocardiogram identified mitral valve prolapse with moderate eccentric mitral valve regurgitation, and a 0.3 × 0.6-cm vegetation was found on the left mitral valve. All of these results meet the modified Duke criteria.

INTERVENTIONS

The abdominal pain and left leg weakness were improving after 2 weeks of intravenous antibiotics treatment. No neurological sequelae were noted after completing the 6-week course of medical treatment.

OUTCOMES

The patient was successfully treated and discharged after completing the 6-week intravenous antibiotics treatment.

LESSONS

IE should be considered in young patients with native valve disease who have prolonged fever. Though S anginosus commonly causes invasive pyogenic infection, patients with native valve disease should be checked for IE.

A Rare Case of Myonecrosis with Soft-Tissue Emphysema in a Diabetic Foot Caused by Streptococcus anginosus Isolated in Pure Culture: A Case Study

Streptococcus anginosus (SAG) is a known human pathogen and member of the Streptococcus milleri group. SAG is a known bacterial cause of soft-tissue abscesses and bacteremia and is an increasingly prevalent pathogen in infections in patients with cystic fibrosis. We describe a rare case of SAG as an infectious agent in a case of nonclostridial myonecrosis with soft-tissue emphysema. This is the only case found in the literature of SAG cultured as a pure isolate in this type of infection and was associated with a prolonged course of treatment in an otherwise healthy patient.

Combating bacterial resistance by combination of antibiotics with antimicrobial peptides

The overuse of antibiotics in the healthcare and agricultural industries has led to the worldwide spread of bacterial resistance. The recent emergence of multidrug resistant (MDR) bacteria has resulted in a call for the development of novel strategies to address this global issue. Research on a diverse range of antimicrobial peptides (AMPs) has shown promising activity against several resistant strains. Increased understanding of the mode of action of AMPs has shown similarity and complementarity to conventional antibiotics and the combination of both has led to synergistic effects in some cases. Combination therapy has been widely used to combat MDR bacterial infections and the recent focus on their application with AMPs may allow antibiotics to be effective against resistant bacterial strains. By conjugation of an antibiotic onto an AMP, a compound may be produced with possibly greater activity and with reduced side-effects and toxicity. The AMP in these conjugates may also act as a unique adjuvant for the antibiotic by disrupting the resistance mechanisms used by bacteria thus allowing the antibiotic to once again be effective. This mini-review outlines some of the current and past work in combining AMPs with conventional antibiotics as strategies to address bacterial resistance.

Ludwig Angina after First Aid Treatment: Possible Etiologies and Prevention-Case Report

Ludwig angina is a life-threatening type of soft tissue cellulitis involving 3 compartments on the floor of the mouth including the submental, sublingual, and submandibular spaces bilaterally. Prevention, early recognition, and treatment of Ludwig angina are critical because this is a clinical diagnosis with unpredictable progression. This article describes a rare case of Ludwig angina that evolved from an odontogenic infection and the specific microbiology and clinical course and discusses possible etiologies and prevention.

A rare case of pyogenic pericarditis secondary to Streptococcus constellatus

We report an extremely rare case of purulent pericarditis caused by the normally commensal oral flora, Streptococcus constellatus, a viridans Streptococcal species and member of the S. anginosus group (previously also known by the eponymous 'S. milleri', for American Willoughby Dayton Miller). This case is a previously healthy 71-year-old immunocompetent woman from Arizona who presented with a 5-day history of progressive shortness of breath and chest tightness, and subjective fever and chills, but without history of nausea, vomiting, night sweats, recent travel, autoimmune disease or sick contacts. Early recognition and intervention of purulent pericarditis allow patients like the one outlined in this case to achieve full recovery.

A chinese case of prevotella intermedia and streptococcus constellatus intracranial mixed infection

Streptococcal Species is increasingly recognized as a potentially preventable emerging infection in human's brain with high prevalence around the world. Streptococcus constellatus is one of the most common pathogens. Meanwhile, anaerobic bacteria are the rare causes for intracranial infection. To date, intracranial mixed infection caused by Prevotella intermedia and Streptococcus constellatus has not been reported. We reported a Chinese case to raise the global awareness of severity of the intracranial mixed infection. Here, we illustrated the epidemiological risk factors, clinical manifestations and outcomes of the patient. For patients who suffer from exacerbated brain infection with fetid cerebrospinal fluid, early repeated imaging is urgently needed and empiric antibiotic therapy should consider anaerobic and aerobic bacteria in these situations.

Multiple liver abscess formation and primary gastrointestinal stromal tumor

Gastrointestinal stromal tumors are the most common mesenchymal tumors of the gastrointestinal tract. The introduction of a number of small molecule tyrosine kinase inhibitors has revolutionized the management of metastatic disease. Surgery is the mainstay of management for localized disease. Patients with high risk tumors are treated with adjuvant imatinib. We report the rare presentation of a localized primary small bowel gastrointestinal stromal tumor in association with multiple liver abscesses. Cystic liver lesions should be fully evaluated in gastro intestinal tumor patients to exclude an infective cause. Treatment with intravenous antibiotics resulted in clinical and radiological improvement of the liver abscesses. The small bowel tumor was treated with surgical resection.

Lincosamide resistance mediated by lnu(C) (L phenotype) in a Streptococcus anginosus clinical isolate

OBJECTIVES

Unique resistance to lincosamides (L phenotype) due to the production of nucleotidyltransferases (Lnu) is uncommon among Gram-positive bacteria. The aim of the study was to characterize the L phenotype in a clinical isolate of the Streptococcus milleri group.

METHODS

The strain UCN93 was recovered from neonatal specimens and from the mother's vaginal swab. Identification was confirmed by sequencing of the sodA gene. Antimicrobial susceptibility testing was carried out by the disc diffusion method, while MICs were determined using the agar dilution method. Screening for lnu(A), lnu(B), lnu(C) and lnu(D) genes was performed by PCR. Genetic environment and support were determined by thermal asymmetric interlaced PCR and PCR mapping. The transfer of lincomycin resistance was also attempted by conjugation.

RESULTS

UCN93 was unambiguously identified as Streptococcus anginosus. It was susceptible to all tested antibiotics, except lincomycin (MIC, 8 mg/L) and tetracycline (2 mg/L). The lnu(C) gene was found to be responsible for the L phenotype. It was shown that lnu(C) was associated with a gene coding for a transposase within a structure similar to the transposon MTnSag1, described once in Streptococcus agalactiae. Since MTnSag1 was found to be mobilized by Tn916 and S. anginosus UCN93 harboured a Tn916 transposon, several attempts at transfer were performed but they all failed. The lnu(C)-containing genetic element was inserted into a chromosomal intergenic sequence of S. anginosus.

CONCLUSIONS

Since lnu(C) has been detected in only one S. agalactiae clinical isolate so far, this is its second description among clinically relevant streptococci.

Streptococcus milleri Group Cutaneous Abscess Associated with Insulin Injection to Distal Lower Extremity in an Insulin-Dependent Diabetic Man

Purpose

We report a case of Streptococcus milleri group (SMG)-associated cutaneous abscess in an older diabetic man. The infection developed after subcutaneous insulin injection to the distal lower extremity. This is the first known account of SMG-associated abscess secondary to insulin administration.

Summary

A 60-year-old Caucasian insulin-dependent diabetic male developed a severe cutaneous infection including abscess and surrounding cellulitis at the site of a self-administered insulin glargine injection on the medial portion of his right lower leg. The infection developed rapidly within 1 day following the injection. Cultures from purulent drainage were positive for SMG. The infection resolved rapidly with an antibiotic regimen including 1 dose of clindamycin followed by intravenous pipercillin/tazobactam plus vancomycin and concluded with outpatient treatment with sulfamethoxazole/trimethoprim. Organisms belonging to SMG are increasingly recognized as pyogenic pathogens responsible, most commonly, for abscess infections. SMG infections have been reported in diabetics; however, this is the first known case of SMG-associated abscess secondary to subcutaneous insulin administration.

Conclusion

A 60-year-old diabetic male experienced a severe SMG-associated abscess in the distal lower extremity after self-injection with insulin glargine. The infection resolved rapidly with intravenous and oral antibiotics. Clinicians should be aware of the potential for abscess infection from SMG at insulin injection sites.

Anaerobic Pseudomonas aeruginosa and other obligately anaerobic bacterial biofilms growing in the thick airway mucus of chronically infected cystic fibrosis patients: an emerging paradigm or "Old Hat"?

INTRODUCTION

The cystic fibrosis (CF) airway mucus is an ideal niche in which many bacteria can develop antibiotic- and phagocyte-resistance in unique structures known as "mode II biofilms" where bacteria are embedded within the mucus, yet unattached to airway epithelial cells. Pseudomonas aeruginosa is the dominant CF pathogen, yet herein the authors provide burgeoning evidence that obligate anaerobic bacteria (e.g., Prevotella) actually thrive within the CF mucus, a paradigmatic shift that chronic CF is an "aerobic" disease. Interestingly, CF organisms repress virulence factor production (e.g., P. aeruginosa) while others (e.g., S. aureus) increase them under anaerobic conditions.

AREAS COVERED

The authors shed additional light on (i) the anoxic nature of the CF airway mucus, (ii) the relative commonality of anaerobic bacteria isolated from CF sputum, (iii) virulence factor production and cross-talk between obligate anaerobes and P. aeruginosa relative to disease progression/remission, (iv) the role of mucoidy in CF, and (v) the role of nitrosative stress in activation of bacteriophage and pyocins within biofilms.

EXPERT OPINION

The authors conclude with insight as to how we might treat some CF bacteria during mode II biofilm infections that utilizes a metabolite of bacterial anaerobic respiration and an aerobic oxidation product of airway-generated NO, acidified NO(2)(-).

Streptococcus milleri in intraabdominal abscesses in children after appendectomy: incidence and course

INTRODUCTION

Intraabdominal abscesses are a common complication after appendectomy, especially in children. In this study, we describe the incidence and course of this complication in relation to the cultured pathogens found in intraabdominal abscesses.

METHODS

The charts of all patients between 1 and 18 years of age undergoing appendectomy in 3 hospitals between January 2006, and July 2009, were retrospectively reviewed. Presence of an intraabdominal abscess was confirmed with abdominal ultrasound examination. We collected all details concerning the appendectomy, pus cultures, and postoperative course in these patients.

RESULTS

Two hundred fifty-nine patients underwent appendectomy during the study period. Subsequently, abdominal ultrasound studies showed an intraabdominal abscess in 18 (7%) patients. Intraabdominal abscesses developed more frequently after perforated appendicitis (23%) than after simple appendicitis (2%). The incidence of postoperative abscesses did not differ significantly between open (5.6%) or laparoscopic (6.3%) appendectomy. However, the rate was high (38%) in the patients in whom the appendectomy was converted from laparoscopic to open. In 15 out of the 18 patients with a postoperative abscess drainage was performed. In pus cultures of the drained abscesses Streptococcus milleri and Escherichia coli were the most commonly isolated pathogens. Presence of S milleri was associated with prolonged hospital stay (13.9 versus 9.0 days, P = .105) and prolonged antibiotic treatment (11.3 versus 4.8 days, P = .203).

CONCLUSIONS

The incidence of intraabdominal abscesses is high after perforated appendicitis in children (23%). Our data suggest that the presence of S milleri correlates with a more complicated postoperative course after appendectomy in children.

Photoactivated disinfection of Streptococcus intermedius through dentin disc at clinically relevant intervals: an in vitro study

In this present study we have tested the impact of porfimer sodium (Photofrin, AXCAN PHARMA Inc., Quebec, Canada) photoactivated disinfection (PD) on cells of Streptococcus intermedius in suspension. In order to provide basic data to support future clinical studies of PD in dentistry the study used exposure to Quartz-tungsten-halogen (QTH) dental curing light for clinically relevant time periods to activate Photofrin and measured its effectiveness under a variety of conditions including activation through dentin hard tissue. S. intermedius was grown in planktonic suspension for 48h. Nine groups were formed: three control groups (1-3) and six experimental groups (4-9). Groups 4-6 tested the use of Photofrin treatment combined with QTH light at various intervals of irradiation (5, 15 and 60s). Groups 7-9 were similar to groups 4-6 with the exception that irradiation commenced through a dentin disc. Following treatment, bacteria were plated. Colony counts were measured following 72h incubation at 37 degrees C. Statistical analysis was carried out by one-way ANOVA at a 95% confidence level. A significant reduction in S. intermedius colony counts was observed for all experimental groups and one control group. The reduction in numbers of colonies in the experimental groups varied from 79.28 to 99.40% with an average of 94.61%. Reduction in viable bacterial cells indicated a strong relationship between power density and irradiation interval. When curing light energy density was lower due to the irradiation through the 1mm dentin disc, prolonged irradiation interval enhanced bacterial kill. In conclusion, where direct irradiation is not possible for PD treatment, irradiation through dentin may still be done successfully within a clinically relevant interval.

Osteoradionecrosis contains a wide variety of cultivable and non-cultivable bacteria

Background

Direct microscopy, anaerobic culture and DNA–DNA hybridization have previously demonstrated an association between microorganisms and osteoradionecrosis (ORN). The purpose of our study was to use culture independent molecular techniques to detect bacteria in necrotic bone lesions of the mandible after radiation therapy.

Design

Bacterial DNA was extracted from eight deep medullar specimens from resected mandibles (six cases), including one patient with relapse. 16S rRNA genes were PCR amplified, cloned, transformed into Escherichia coli and sequenced to determine species identity and closest relatives.

Results

From the analysis of 438 clones, 59 predominant species were detected, 27% of which have not been cultivated. The predominant species detected from radionecrotic mandibles were Campylobacter gracilis, Streptococcus intermedius, Peptostreptococcus sp. oral clone FG014, uncultured bacterium clone RL178, Fusobacterium nucleatum, and Prevotella spp. The study demonstrated intersubject variability of the bacteria present in ORN. In contrast to the diverse bacterial profile detected in primary infection, only a few members of the oral indigenous flora were identified from the relapse case.

Conclusions

Diverse bacterial profiles in specimens of ORN in marrow spaces of the mandible were detected by culture independent molecular techniques. To better understand the pathogenesis and to improve the therapy of the infection, detection of all members of the complex bacterial flora associated with ORN is necessary.

Development of real-time PCR assays for detection of the Streptococcus milleri group from cystic fibrosis clinical specimens by targeting the cpn60 and 16S rRNA genes

Cystic fibrosis (CF) is a multiorgan disease, with the majority of mortalities resulting from pulmonary failure due to repeated pulmonary exacerbations. Recently, members of the Streptococcus anginosus group (S. anginosus, S. constellatus, and S. intermedius), herein referred to as the "Streptococcus milleri group" (SMG) have been implicated as important etiological pathogens contributing to pulmonary exacerbations in CF patients. This is partly due to better microbiological detection of the SMG species through the development of a novel specific medium termed "McKay agar." McKay agar demonstrated that SMG has been an underreported respiratory pathogen contributing to lung exacerbations. Our aim was to develop a real-time PCR assay to expedite the detection of SMG within diagnostic samples. The cpn60 gene was chosen as a target, with all three members amplified using a single hybridization probe set. SMG strain analysis showed that speciation based on melting curve analysis allowed for the majority of the S. constellatus (96%), S. intermedius (94%), and S. anginosus (60%) strains to be correctly identified. To increase specificity for S. anginosus, two 16S rRNA real-time PCR assays were developed targeting the 16S rRNA gene. The 16s_SA assay is specific for S. anginosus (100%), while the 16s_SCI assay is specific for S. constellatus and S. intermedius (100%). These assays can detect <10 genome equivalents in pure culture and >10(4) genome equivalents in sputum samples, making this a great tool for assessment of the presence of SMG in complex polymicrobial samples. Novel molecular methods were developed providing detection ability for SMG, an emerging opportunistic pathogen.

Evaluation of genotypic and phenotypic methods for differentiation of the members of the Anginosus group streptococci

The terminology and classification of the Anginosus group streptococci has been inconsistent. We tested the utility of 16S rRNA gene and tuf gene sequencing and conventional biochemical tests for the reliable differentiation of the Anginosus group streptococci. Biochemical testing included Rapid ID 32 Strep, API Strep, Fluo-Card Milleri, Wee-tabs, and Lancefield antigen typing. Altogether, 61 Anginosus group isolates from skin and soft tissue infections and four reference strains were included. Our results showed a good agreement between 16S rRNA gene and tuf gene sequencing. Using the full sequence was less discriminatory than using the first part of the 16S rRNA gene. The three species could not be separated with the API 20 Strep test. Streptococcus intermedius could be differentiated from the other two species by β-galactosidase (ONPG) and β-N-acetyl-glucosaminidase reactions. Rapid ID 32 Strep β-glucosidase reaction was useful in separating S. anginosus strains from S. constellatus. In conclusion, both 16S rRNA gene and tuf gene sequencing can be used for the reliable identification of the Anginosus group streptococci. S. intermedius can be readily differentiated from the other two species by phenotypic tests; however, 16S rRNA gene or tuf gene sequencing may be needed for separating some strains of S. constellatus from S. anginosus.

Corneal ulceration due to vitamin A deficiency in Zellweger syndrome

We report a case of vitamin A deficiency and secondary corneal ulcer in an infant with Zellweger syndrome. A 7-month-old infant with failure to thrive and malnutrition developed a corneal ulcer. Fortified antibiotic eye drops were administered without improvement. Vitamin A deficiency was suspected and confirmed. Supplementation with oral vitamin A decreased corneal opacification. Zellweger syndrome was later diagnosed. Vitamin A deficiency should be considered in the differential diagnosis of nonhealing corneal ulcers in children, especially those with systemic syndromes and failure to thrive.

A polymicrobial perspective of pulmonary infections exposes an enigmatic pathogen in cystic fibrosis patients

Lung disease is the leading cause of morbidity and mortality in cystic fibrosis (CF) patients. A modest number of bacterial pathogens have been correlated with pulmonary function decline; however, microbiological and molecular evidence suggests that CF airway infection is polymicrobial. To obtain a more complete assessment of the microbial community composition and dynamics, we undertook a longitudinal study by using culture-independent and microbiological approaches. In the process, we demonstrated that within complex and dynamic communities, the Streptococcus milleri group (SMG) can establish chronic pulmonary infections and at the onset of 39% of acute pulmonary exacerbations, SMG is the numerically dominant pathogen. We report the comprehensive polymicrobial community dynamics of a CF lung infection in a clinically relevant context. If a given organism, such as Pseudomonas aeruginosa, becomes resistant to antibiotic therapy, an alternative treatment avenue may mediate the desired clinical response by effectively managing the composition of the microbial community.

Culture-Negative intracerebral abscesses in children and adolescents from Streptococcus anginosus group infection: a case series

We report the use of 16S ribosomal RNA gene amplification and sequencing to diagnose culture-negative intracerebral abscesses in younger patients. These 3 cases demonstrate the optimal application of gene sequencing from direct specimens for patients with negative culture results compromised by antibacterial therapy but histories highly suggestive of acute bacterial infection.

In vitro susceptibility of the Streptococcus milleri group to antimicrobial peptides

AIM

To determine the susceptibility of strains of the Streptococcus milleri group (SMG) to commercially available antimicrobial peptides.

METHODOLOGY

Thirty strains of SMG from a range of sources were assessed for their susceptibility to 10 antimicrobial peptides of either human, animal or insect origin, using a double layer diffusion assay.

RESULTS

The majority of the test strains were sensitive to the amidated peptides, mastoparan (100%; n = 30), magainin 2 amide (95%; n = 21) and indolicin (91%; n = 23). Some strains were susceptible to cecropin B (30%; n = 30) and histatin (10%; n = 30), whilst no activity was observed for the defensins HNP-1 and HNP-2, histatin 8, cecropin P1 and magainin 2.

CONCLUSIONS

The majority of strains were resistant to the human derived peptides. The ability to resist such peptides may be a factor in the colonisation of the oral cavity and the survival and initiation of infection in the pulp and root canal environment. Interestingly, the present study indicated that amidated and alpha helical peptides exhibit antimicrobial activity against SMG. Structural modification of these peptides may allow a targeted approach for the development of these substances as preventative or therapeutic agents.

The Streptococcus milleri group--an unrecognized cause of disease in cystic fibrosis: a case series and literature review

The "Streptococcus milleri" group (SMG) is increasingly recognized for their role in pyogenic infections including empyema and solid organ abscesses. However, SMG disease has rarely been identified in cystic fibrosis (CF). Inherent difficulties in both growing the organisms and distinguishing SMG from less virulent oropharyngeal viridans streptococci may have led to a decreased recognition of this as a CF pathogen. We report on six cases of SMG-related infection over a 4-year time-frame occurring within an adult CF clinic in Canada, and a further four cases identified through a literature review. SMG manifested disease as bronchopulmonary exacerbations in 7 of 10 patients, and 4 of 10 patients had extra-pulmonary dissemination of SMG infection. Noticeably, pulmonary exacerbations were frequently associated with atypically malodorous sputum. Furthermore, patients clinically responded to anti-microbial therapies with no anti-Pseudomonal activity. There was a consistent correlation of SMG disease and co-colonization with P. aeruginosa leading to speculation of polymicrobial interactions resulting in enhanced virulence. SMG deserves considerable attention as a potential pathogen within the airways of patients with CF.

Synthetic bromated furanone inhibits autoinducer-2-mediated communication and biofilm formation in oral streptococci

INTRODUCTION

Autoinducer-2 (AI-2) is a widespread communication-signal molecule that allows bacteria to sense and react to environmental factors. In some streptococci AI-2 is reported to be involved in virulence expression and biofilm formation. It has earlier been shown that the alga Delisea pulchra produces bromated furanones, which prevent bacterial colonization of the algae.

METHODS AND RESULTS

We have previously published a novel and simple synthesis of (Z)-5-bromomethylene-2(5H)-furanone. In this study we showed that our synthesized furanone inhibited biofilm formation and bioluminescence induction by Streptococcus anginosus, Streptococcus intermedius, and Streptococcus mutans, as well as bioluminescence induction by Vibrio harveyi BB152.

CONCLUSION

We suggest that the effect is linked to interference with the AI-2 signaling pathway because adding furanone to the medium had no effect on the ability of the AI-2-defective S. anginosus luxS and S. intermedius luxS mutants to form biofilms.

Relevance of Group Milleri Streptococci in Thoracic Surgery: A Clinical Update

Group Milleri streptococci (GMS), a heterogeneous group of streptococci, are associated with purulent infections. This study was a retrospective analysis of all consecutive thoracic infections of GMS between 2001 and 2004. Of 246 surgical GMS infections, thoracic infections accounted for 4.5 per cent, including 10 pleural infections (eight empyemas and two infected pleural effusions) and one mediastinal infection. The etiology of pleural infection was parapneumonic (7), second to esophageal perforation (1), liver transplantation (1), and liver resection (1). Polymicrobial infections were present in 64 per cent. All patients underwent removal of the infected masses, including drainage (3), thoracoscopic decortication (5), thoracotomy with debridement (2), and incision with drainage (1). The case fatality rate was 9 per cent (there was one patient with congestive heart disease unfit to undergo surgical empyema evacuation) and the recurrence rate was 27.3 per cent (three patients). Combined antibiotic/surgical treatment was successful in all other cases. GMS isolates were susceptible to clindamycin and all β-lactam antibiotics except ceftazidime, but were resistant to aminoglycosides. If found intrathoracically, GMS frequently progress to severe empyema. Therefore, timely removal of pleural collection by percutaneous drainage or surgical intervention seems indicated. If surgery is required, thoracoscopic decortication may be the preferred approach.

Group milleri streptococci: significant pathogens in solid organ recipients

Group milleri streptococci (GMS) comprise a heterogeneous group of streptococci including the species intermedius, constellatus and anginosus. They may cause chronic intra-abdominal and intrathoracic abscesses, which are difficult to treat. This is a retrospective analysis including 45 transplant recipients in whom GMS were isolated. The epidemiology, clinical significance and the impact on the outcome in all transplant patients with infections caused by GMS during a 4-year period (2001-2004) was evaluated. The 45 solid organ recipients (88 isolates) included 34 liver-, four kidney/pancreas-, one kidney-, two small bowel-, three combined liver/kidney- and one combined kidney/small bowel transplant recipient. In 42 cases GMS caused intra-abdominal infection, in two cases pleural empyema and in one case soft tissue infection. Only a single isolate of GMS was cultured from blood. In 54 of the 88 specimens (61%), which grew GMS, other pathogens were also isolated. GMS frequently caused recurrent cholangitis (n = 17) associated with anastomotic and nonanastomotic biliary strictures. These cases were managed by repeated stenting or surgical intervention and prolonged antibiotic therapy. No patient died directly related to GMS infection and all except one case responded to combined surgical/antibiotic treatment. One pancreas graft was lost because of erosion haemorrhage associated with an abscess. GMS were susceptible to penicillin G, carbapenems and clindamycin, whereas cephalosporins and quinolones showed intermediate activity or resistance in some cases, and GMS in general were found resistant to aminoglycosides. GMS may cause serious infections in transplant recipients which are difficult to treat. Their prevalence in transplant surgical site infections thus far may have been underestimated.

LuxS-mediated signalling in Streptococcus anginosus and its role in biofilm formation

The autoinducer-2 signal (AI-2) produced by several Gram-positive and Gram-negative bacteria mediates interspecies communication. In this study we were able to identify an orthologue of luxS, required for the synthesis of AI-2 signals, in Streptococcus anginosus. Comparative analyses revealed conserved sequences in the predicted S. anginosus LuxS. Expression of luxS was highest during early exponential growth phase. Compared to other oral streptococci, conditioned media from growth of members of the anginosus group were the most efficient in inducing bioluminescence in Vibrio harveyi, indicative of AI-2 signalling. Disruption of luxS in S. anginosus resulted in a mutant deficient in biofilm formation, whereas no effect on planktonic growth rate was observed under various growth conditions. S. anginosus is part of the human flora found in biofilms of the oral cavity, as well as of the upper respiratory, gastrointestinal and urogenital tracts. Such habitats harbour large varieties of bacterial species, among which cell-cell communication may play an important role. S. anginosus has also been associated with purulent infections and cancer in the upper digestive tract. Knowledge about the molecular mechanisms involved in S. anginosus communication is important for understanding its commensalism and its pathogenic transition.

Involvement of antigen I/II surface proteins in Streptococcus mutans and Streptococcus intermedius biofilm formation

BACKGROUND/AIM

Dental diseases are caused by microorganisms organized in biofilms. Streptococcus mutans and Streptococcus intermedius are commensals of the human oral cavity. S. mutans is associated with caries, whereas S. intermedius is associated with purulent infections. Oral streptococci including S. mutants and S. intermedius express a family of surface proteins termed antigen I/II (Ag I/II). Ag I/II is implicated in adhesion; however, its role in biofilm formation has not yet been investigated.

METHODS

By using isogenic Ag I/II-deficient mutants of S. mutans and S. intermedius we studied the influence of Ag I/II on in vitro biofilm formation. Biofilm was quantified in polystyrene microtiter plates and visualized by scanning electron microscopy. Ag I/II expression in planktonic and biofilm cells, as well as in the presence or absence of saliva was investigated by immunoblotting.

RESULTS

In the presence of saliva, the Ag I/II-deficient mutants formed 65% less biofilm than the wild-types. In the absence of saliva, no difference was observed in S. mutans, whereas the S. intermedius Ag I/II mutant formed 41% less biofilm. Ag I/II expression was reduced in the presence of saliva. No differences in expression were observed between biofilm and planktonic cells.

CONCLUSION

The results indicated that Ag I/II may be important during biofilm formation particularly in the presence of saliva. These findings may provide useful information regarding the importance of Ag I/II in biofilm formation and in the search of new strategies to control biofilm-mediated infections.

Suppurative intracranial complications of sinusitis in previously healthy children

In this retrospective case series, we describe the clinical features and microbiology of 16 previously healthy children with suppurative intracranial complications of sinusitis. Most cases were male adolescents who presented with vomiting in addition to typical sinusitis symptoms. Neurologic signs were often absent. Streptococcus milleri group organisms, along with anaerobes, were common pathogens.

Frequent and preferential infection of Treponema denticola, Streptococcus mitis, and Streptococcus anginosus in esophageal cancers

Multiple cancers frequently occur in the upper digestive tract. One possible explanation is that specific bacterial infection stimulates the normal epithelium to initiate inflammation and/or promotes carcinogenesis. This study was undertaken to determine which bacterial species is predominantly associated with esophageal cancer. We examined the bacterial diversity in this type of cancer and in the saliva from healthy people by using a culture-independent molecular method. Here we report the preferential and frequent infection of the oral periodontopathic spirochete Treponema denticola (T. denticola), Streptococcus mitis (S. mitis), and Streptococus anginosus (S. anginosus) in esophageal cancer from different regions of the world, and we also describe the induction of inflammatory cytokines by infection of S. anginosus and S. mitis. Our present data suggest that these three bacteria could have significant roles in the carcinogenic process of many cases of esophageal cancer by causing inflammation and by promoting the carcinogenic process, and that eradication of these three bacteria may decrease the risk of recurrence.

Intracerebral abscess in children: historical trends at Children's Hospital Boston

OBJECTIVES

A previous study performed at Children's Hospital Boston describing the natural history of intracerebral abscess between 1945 and 1980 demonstrated a decline in mortality after 1970. This current study examines the occurrence of intracerebral abscess at Children's Hospital Boston between 1981 and 2000, inclusive, and compares the results with the previous study. Our objectives were to determine whether there had been a change in the predisposing factors, whether there were changes in the microbiology of intracerebral abscesses, and whether mortality rate had continued to decline.

METHODS

To ensure that all occurrences of intracerebral abscess treated at Children's Hospital Boston between 1981 and 2000 were identified, we searched 4 separately maintained databases for the keywords "brain" or "abscess" or the International Classification of Diseases, Ninth Revision code 324.x. This search yielded the names of 386 patients. Of these 386 patients, a solitary intracerebral abscess or multiple noncontiguous intracerebral abscesses could be confirmed in 54 patients on the basis of cranial imaging (computed tomography or magnetic resonance imaging) or autopsy reports. The complete retrospective review of the medical records of these 54 patients constitutes the basis for this study.

RESULTS

Congenital heart disease was the most common predisposing factor during both eras. Compared with the previous era, important historical trends identified include a reduction in the number of abscesses that occurred in the settings of sinus or otitic infection (11% during 1981-2000 vs 26% during 1945-1980), an increase in number of intracranial abscesses in infants (18% vs 7%) and in the setting of immunosuppression (16% vs 1%), an increase in the number of children who were treated with antibiotics alone (22% vs 1%), a stable overall mortality rate (24% vs 27%), and the identification of Citrobacter and fungus as causes of intracranial abscess not observed during the previous era of 1945-1980. Citrobacter was observed only during the neonatal period. Fungi were the causative organisms predominantly in the setting of immunosuppression.

CONCLUSIONS

Intracerebral abscess in children continues to be associated with high rates of neurologic impairment and death. Because earlier detection may reduce morbidity and mortality, intracranial abscess should be considered when evaluating children with new-onset neurologic signs or symptoms, especially in children who have acute immunosuppression and disseminated fungal disease or fungemia.

The role of the capsule of the Streptococcus milleri group in its pathogenicity

Study of the pathogenicity of encapsulated strains of the Streptococcus milleri group (SMG) was performed by examination of the ability to cause subcutaneous abscesses in mice and by phagocytosis and phagocytic killing of human polymorphonuclear neutrophils (PMNs) against the organisms. All 3 encapsulated isolates from patients with pneumonia or lung abscess induced abscesses in the mice; however, only 2 of 20 unencapsulated isolates from patients with lung abscess or thoracic empyema did so. The 3 encapsulated strains inhibited more phagocytosis and phagocytic killing of PMNs than the unencapsulated strains. In addition, encapsular material separated from Streptococcus constellatus RZYK001 also inhibited phagocytosis and phagocytic killing in proportion to increasing concentrations of the capsular material. These results suggest that capsular material produced by SMG might be a pathogenic factor.

Different frequencies of Streptococcus anginosus infection in oral cancer and esophageal cancer

Multiple cancers frequently occur in the upper aerodigestive tract. The high incidence rate of multiple carcinomas in this region is often explained in terms of involvement of the same underlying risk factors. It has been reported that the oral bacterium Streptococcus anginosus (S. anginosus) is associated with esophageal, gastric, and pharyngeal cancer tissues. In this study, a highly specific quantification method for S. anginosus DNA using real-time PCR was established. We employed this assay to determine whether S. anginosus is also associated with oral cancer tissues. This precise quantification method revealed different degrees of infection with S. anginosus in esophageal cancer and oral cancer. We assayed 10 ng of genomic DNA from cancer tissues, and found that eight of 18 samples (44%) from the esophagus contained a detectable level (>10 fg) of S. anginosus DNA, whereas this was the case for only five of 38 samples (13%) of oral cancer. The quantity of S. anginosus DNA in the esophageal cancer tissues was significantly higher than in oral cancer. The maximum amount of S. anginosus DNA was approximately ten times higher in esophageal than in oral cancer tissues. In addition, none of the five different oral cancer sites (floor of the mouth, mandibular gingival, maxillary gingival, buccal mucosal, and tongue) showed significant signs of S. anginosus infection. On the other hand, most non-cancerous tissues of the esophagus and tongue showed an undetectable level of S. anginosus. These results suggest that S. anginosus is associated with esophageal cancer, but is not closely related with oral cancer.

Differences in the betaC-S lyase activities of viridans group streptococci

betaC-S Lyase catalyzes the alpha,beta-elimination of L-cysteine to hydrogen sulfide, which is one of the main causes of oral malodor and is highly toxic to mammalian cells. We evaluated the capacity of six species of oral streptococci to produce hydrogen sulfide. The crude enzyme extract from Streptococcus anginosus had the greatest capacity. However, comparative analysis of amino acid sequences did not detect any meaningful differences in the S. anginosus betaC-S lyase. The capacity of S. anginosus purified betaC-S lyase to degrade L-cysteine was also extremely high, while its capacity to degrade L-cystathionine was unremarkable. These findings suggest that the extremely high capacity of S. anginosus to produce hydrogen sulfide is due to the unique characteristic of betaC-S lyase from that organism.

Antibody-based diagnostic for 'refractory' periodontitis

OBJECTIVE

About 10-15% of US adults are 'refractory' to therapy for chronic periodontitis. Recently, studies suggest that these patients have elevated lysine decarboxylase activity in the sulcular microbiota. The aim of this study was to determine whether an elevated IgG antibody response to lysine decarboxylase, alone or with antibody to other bacterial antigens and baseline clinical measurements, would predict 'refractory' patients with high accuracy.

METHODS

Chronic periodontitis patients were treated using scaling and root planing (SRP) followed by maintenance SRP and 3-monthly re-examinations. If there was a loss of mean full mouth attachment or more than three sites appeared with > 2.5 mm new loss within a year, the subjects were re-treated (modified Widman flap surgery and systemically administered tetracycline). If attachment loss as above recurred, the subjects were 'refractory'. Baseline clinical measurements and specific antibody responses were used in a logistic regression model to predict 'refractory' subjects.

RESULTS

Antibody to a peptide portion of lysine decarboxylase (HKL-Ab) and baseline bleeding on probing (BOP) prevalence measurements predicted attachment loss 3 months after initial therapy [pIAL = loss (0) or gain (1)]. IgG antibody contents to a purified antigen from Actinomyces spp. (A-Ab) and streptococcal d-alanyl glycerol lipoteichoic acid (S-Ab) were related in 'refractory' patients (R2 = 0.37, p < 0.01). From the regression equation, the relationship between the antibodies was defined as linear (pLA/S-Ab = 0) or non-linear pLA/S-Ab = 1). Using pLA/S-Ab, pIAL and age, a logistic regression equation was derived from 48 of the patients. Of 59 subjects, 37 had 2-4 mm attachment loss and were assigned as 'refractory' or successfully treated with 86% accuracy.

CONCLUSION

HKL-Ab facilitated an accurate prediction of therapeutic outcome in subjects with moderate periodontitis.

Functional variation of the antigen I/II surface protein in Streptococcus mutans and Streptococcus intermedius

Although Streptococcus intermedius and Streptococcus mutans are regarded as members of the commensal microflora of the body, S. intermedius is often associated with deep-seated purulent infections, whereas S. mutans is frequently associated with dental caries. In this study, we investigated the roles of the S. mutans and S. intermedius antigen I/II proteins in adhesion and modulation of cell surface characteristics. By using isogenic mutants, we show that the antigen I/II in S. mutans, but not in S. intermedius, was involved in adhesion to a salivary film under flowing conditions, as well as in binding to rat collagen type I. Binding to human fibronectin was a common function associated with the S. mutans and S. intermedius antigen I/II. Adhesion of S. mutans or S. intermedius to human collagen types I or IV was negligible. Hydrophobicity, as measured by water contact angles, and zeta potentials were unaltered in the S. intermedius mutant. The S. mutans isogenic mutants, on the other hand, exhibited more positive zeta potentials at physiological pH values than did the wild type. The results indicate common and species-specific roles for the antigen I/II in mediating the attachment of S. mutans and S. intermedius to host components and in determining cell surface properties.