Fusobacteria: new taxonomy and related diseases

Mesenteric adenitis and portal vein thrombosis due to Fusobacterium nucleatum

We report the first description of portal and mesenteric vein thrombosis associated with suppurative mesenteric adenitis in a 71-year-old woman. The bacterium detected in mesenteric lymph nodes was Fusobacterium nucleatum, an anaerobic Gram-negative bacillus. Our patient had a clinical syndrome of pharyngitis and fever preceding portal vein thrombosis. Abdominal symptoms improved with antibiotics and anticoagulant therapy. This location of F. nucleatum in mesenteric lymph nodes provides an interesting insight into the occurrence of septic thrombosis in the portal vein following pharyngo-tonsillar infection.

Bilateral Lemierre's Syndrome: A Case Report and Literature Review

Lemierre's syndrome is characterized by thrombosis of the internal jugular vein that develops following an oropharyngeal infection. Sepsis and septic metastases frequently ensue and affect the lungs, the musculoskeletal system, and occasionally the liver. Most cases are caused by infection with Fusobacterium necrophorum. This infection responds to antibiotic therapy with beta-lactamase-resistant compounds that exert good anaerobic coverage. Anticoagulation and surgical intervention can be helpful in advanced cases. Fewer than 160 cases of classic Lemierre's syndrome have been described; approximately one-third of these reported cases have occurred since 1988. We describe a new case of Lemierre's syndrome that occurred in an otherwise healthy 27-year-old man. Thrombosis of both internal jugular veins extended through the subclavian system and into both upper extremities. The patient was treated with intravenous antibiotics and heparin during 14 days of hospitalization. He was discharged on oral clindamycin and warfarin sodium, and after 6 months he was able to return to full activity. To our knowledge, this is the first reported case of Lemierre's syndrome in which internal jugular vein thrombosis occurred bilaterally. By reporting this previously undescribed manifestation of Lemierre's syndrome, we hope to increase practitioner awareness of this disease entity.

Changes in the bacterial flora of the neoterminal ileum after ileocolonic resection for Crohn's disease

OBJECTIVE

Bacterial agents have been implicated in the early recurrence of Crohn's disease after ileocolectomy. The aim of our study was to identify and quantify bacteria associated with the ileal mucosa in patients and controls and to correlate specific bacteria with recurrence.

METHODS

The predominant bacterial microflora of the ileum were enumerated and identified, aerobically and anaerobically, in biopsies obtained at the time of surgery or by endoscopy from 61 patients with Crohn's disease and 10 ileocolectomy controls. The 61 specimens were comprised of 13 ileal biopsies taken from resection specimens, seven taken after ileostomy, and 41 taken after ileocolectomy.

RESULTS

Ileocolectomy induced a significant increase in bacterial counts and variety in the neoterminal ileum in both patients and controls that was not observed in ileostomy biopsies. Comparison between patients and controls revealed greater numbers of Escherichia coli and enterococci in Crohn's disease and of bifidobacteria and ruminococci in controls. Early recurrence was associated with high counts of E. coli and bacteroides and the frequent isolation of fusobacteria.

CONCLUSION

After ileocolectomy, colonization of the neoterminal ileum is increased. Our data suggest that increases in the populations of specific bacteria such as E. coli, enterococci, bacteroides, and fusobacteria may be important in postoperative recurrence of Crohn's disease.

Purification and characterization of beta-methylaspartase from Fusobacterium varium

Beta-methylaspartase (EC 4.3.1.2) was purified 20-fold in 35% yield from Fusobacterium varium, an obligate anaerobe. The purification steps included heat treatment, fractional precipitation with ammonium sulfate and ethanol, gel filtration, and ion exchange chromatography on DEAE-Sepharose. The enzyme is dimeric, consisting of two identical 46 kDa subunits, and requires Mg2+ (Km = 0.27+/-0.01 mM) and K+ (Km = 3.3+/-0.8 mM) for maximum activity. Beta-methylaspartase-catalyzed addition of ammonia to mesaconate yielded two diastereomeric amino acids, identified by HPLC as (2S,3S)-3-methylaspartate (major product) and (2S,3R)-3-methylaspartate (minor product). Optimal activity for the deamination of (2S,3S)-3-methylaspartate (Km = 0.51+/-0.04 mM) was observed at pH 9.7. The N-terminal protein sequence (30 residues) of the F. varium enzyme is 83% identical to the corresponding sequence of the clostridial enzyme.

Hemolytic uremic syndrome in an adolescent with Fusobacterium necrophorum bacteremia

Microorganisms may produce substances that disrupt the interaction between platelets and vascular endothelium, which has been associated with atypical hemolytic uremic syndrome (HUS). We present the first reported case of Fusobacterium necrophorum bacteremia that presented initially with atypical HUS. Antimicrobial therapy eradicated the patient's bacteremia, and plasmapheresis restored platelet-endothelial homeostasis. Understanding the pathophysiologic mechanisms involved in atypical HUS would guide the development of more precise therapies.

Human necrobacillosis, with emphasis on Lemierre's syndrome

Lemierre's syndrome is the classical presentation of human necrobacillosis. It is characterized by a primary infection in the head in a young, previously healthy person who subsequently develops persistent high fever and disseminated metastatic abscesses, frequently including a septic thrombophlebitis of the internal jugular vein. The main pathogen is Fusobacterium necrophorum, an obligate anaerobic, pleomorphic, gram-negative rod. Clinical microbiologists have a key role in alerting clinicians and advising proper antibiotic treatment when the characteristic microscopic morphology of the pleomorphic F. necrophorum is seen in Gram stains from positive anaerobic cultures of blood and pus. Early diagnosis and prolonged appropriate antibiotic treatment with good anaerobic coverage are crucial to reduce morbidity and mortality. F. necrophorum also causes human necrobacillosis with foci caudal to the head, mainly in elderly patients with high mortality related to age and predisposing diseases, such as cancers of the primary focus.

Acquisition of plasmin activity by Fusobacterium nucleatum subsp. nucleatum and potential contribution to tissue destruction during periodontitis

Fusobacterium nucleatum subsp. nucleatum has been associated with a variety of oral and nonoral infections such as periodontitis, pericarditis, bone infections, and brain abscesses. Several studies have shown the role of plasmin, a plasma serine protease, in increasing the invasive capacity of microorganisms. In this study, we investigated the binding of human plasminogen to F. nucleatum subsp. nucleatum, and its subsequent activation into plasmin. Plasminogen-binding activity of bacterial cells was demonstrated by a solid-phase dot blot assay using an anti-plasminogen antibody. The binding activity was heat resistant and involved cell-surface lysine residues since it was abolished in the presence of the lysine analog epsilon-aminocaproic acid. Activation of plasminogen-coated bacteria occurred following incubation with either streptokinase, urokinase-type plasminogen activator (u-PA), or a Porphyromonas gingivalis culture supernatant. In the case of the P. gingivalis culture supernatant, a cysteine protease was likely involved in the activation. The plasmin activity generated on the cell surface of F. nucleatum subsp. nucleatum could be inhibited by aprotinin. Activation of plasminogen by u-PA was greatly enhanced when plasminogen was bound to bacteria rather than in a free soluble form. u-PA-activated plasminogen-coated F. nucleatum subsp. nucleatum was found to degrade fibronectin, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Tissue inhibitor of metalloproteinase-1 was also degraded by the plasmin activity generated on the bacterial cells. This study suggests a possible role for plasminogen, which is present in affected periodontal sites, in promoting tissue destruction and invasion by nonproteolytic bacteria such as F. nucleatum subsp. nucleatum.

Primary psoas abscess due to Fusobacterium nucleatum

A case of primary pyogenic psoas abscess due to Fusobacterium nucleatum is described. Clinicians must maintain a high index of clinical suspicion for the diagnosis of psoas abscess. Although Staphylococcus aureus accounts for most cases of primary psoas abscess, this report emphasizes the importance of bacteriological confirmation of the microorganism involved.

Identification of the cause of a brain abscess by direct 16S ribosomal DNA sequencing

We report the case of a young man who apparently suffered successive episodes of meningitis and cerebral abscess over a 1-month period, both of which were diagnosed by two different molecular approaches; PCR for Neisseria meningitidis IS1106 from CSF and 16S rRNA gene sequencing on a specimen of brain pus. In each case, cultures were negative due to prior antibiotic therapy.

Bacteriocin production by Fusobacterium isolates recovered from the oral cavity of human subjects with and without periodontal disease and of marmosets

Bacteriocin production has been studied in very few anaerobic bacteria, and no report is available for Fusobacterium species. In the present study a total of 167 Fusobacterium isolates were tested for bacteriocin production: 70 isolates were obtained from the oral cavity of patients with periodontal disease, 47 were recovered from healthy oral sites of human subjects and 50 from the oral cavity of Callithrix penicillata. Autoantagonism and isoantagonism were observed when the bacteriocin-producing isolates were tested against themselves. Heteroantagonism was detected by testing the Fusobacterium isolates against 14 reference strains and 2 strains of Actinobacillus actinomycetemcomitans from our laboratory collection. The auto-, iso- and heteroantagonism phenomena observed in this comparative study suggest a possible ecological role for this (these) antagonistic substance(s) in the oral environment.

Studies on fusobacteria associated with periodontal diseases

The physiological and metabolic characteristics of representative isolates of the various subspecies of Fusobacterium nucleatum were investigated by growing them in continuous culture in chemically-defined, media. Behaving almost identically, these organisms were found to obtain energy from the fermentation of simple carbohydrates such as glucose or fructose or from the fermentation of certain amino acids, free or in the form of small peptides. The latter can be attacked by aminopeptidase activity which was shown to be essential for the growth of the organism in an environment lacking fermentable carbohydrate and free amino acids but replete with small peptides. This metabolic versatility may explain the presence of F. nucleatum in both supra- and sub-gingival dental plaque and why it is often found together with organisms such as Porphyromonas gingivalis which display powerful endopeptidase activities. Using the technique of allozyme electrophoresis, the current subspeciation of F. nucleatum was shown to be of doubtful validity and evidence, based upon physiological and metabolic properties, for differences in pathogenicity between isolates was not detected. While this organism is a member of various bacterial consortia associated with periodontal diseases, its contribution to the disease process remains unclear.

6-phospho-alpha-D-glucosidase from Fusobacterium mortiferum: cloning, expression, and assignment to family 4 of the glycosylhydrolases

The Fusobacterium mortiferum malH gene, encoding 6-phospho-alpha-glucosidase (maltose 6-phosphate hydrolase; EC 3.2.1.122), has been isolated, characterized, and expressed in Escherichia coli. The relative molecular weight of the polypeptide encoded by malH (441 residues; Mr of 49,718) was in agreement with the estimated value (approximately 49,000) obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the enzyme purified from F. mortiferum. The N-terminal sequence of the MalH protein obtained by Edman degradation corresponded to the first 32 amino acids deduced from the malH sequence. The enzyme produced by the strain carrying the cloned malH gene cleaved [U-14C]maltose 6-phosphate to glucose 6-phosphate (Glc6P) and glucose. The substrate analogs p-nitrophenyl-alpha-D-glucopyranoside 6-phosphate (pNP alphaGlc6P) and 4-methylumbelliferyl-alpha-D-glucopyranoside 6-phosphate (4MU alphaGlc6P) were hydrolyzed to yield Glc6P and the yellow p-nitrophenolate and fluorescent 4-methylumbelliferyl aglycons, respectively. The 6-phospho-alpha-glucosidase expressed in E. coli (like the enzyme purified from F. mortiferum) required Fe2+, Mn2+, Co2+, or Ni2+ for activity and was inhibited in air. Synthesis of maltose 6-phosphate hydrolase from the cloned malH gene in E. coli was modulated by addition of various sugars to the growth medium. Computer-based analyses of MalH and its homologs revealed that the phospho-alpha-glucosidase from F. mortiferum belongs to the seven-member family 4 of the glycosylhydrolase superfamily. The cloned 2.2-kb Sau3AI DNA fragment from F. mortiferum contained a second partial open reading frame of 83 residues (designated malB) that was located immediately upstream of malH. The high degree of sequence identity of MalB with IIB(Glc)-like proteins of the phosphoenol pyruvate dependent:sugar phosphotransferase system suggests participation of MalB in translocation of maltose and related alpha-glucosides in F. mortiferum.

Postanginal Sepsis Syndrome with Metastatic Lung Abscess in a Young Man

A postanginal Sepsis Syndrome with metastatic lung abscess caused by Fusobacterium necrophorumin a 25-year-old previously healthy man is described. The incomplete and ineffective antibiotic treatment at onset of angina ended progressively in septicaemia and metastatic infections in a 3-week time period. The early parenteral use of Metronidazole based only on the clinical picture, the Gram stain findings and the strict anaerobic feature of the blood isolate in parallel with the long-term antibiotic treatment were possibly the main reasons for the good outcome of this serious infection.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

The use of allozyme electrophoresis to assess genetic heterogeneity among previously subspeciated isolates of Fusobacterium nucleatum

Fusobacterium nucleatum has been implicated in the pathogenesis of periodontal diseases. Five subspecies have previously been proposed. The validity of these subdivisions was investigated using allozyme electrophoresis for 21 enzyme mobilities. The 18 F. nucleatum isolates tested had previously been subspeciated and included type strains as well as isolates from both oral and extraoral sites. The results showed 2 distinct genetic groups with fixed differences at 82.5% of the test loci, indicative of a species complex with a number of subspecies within each of the 2 groups. There was also evidence of a correlation between the 2 major groups of isolates and the site from which they were taken. It was concluded that there is a high degree of genetic heterogeneity within the species F. nucleatum and that its current subspeciation is of questionable validity.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Recurrent vertebral osteomyelitis and psoas abscess caused by Streptococcus constellatus and Fusobacterium nucleatum in a patient with atrial septal defect and an occult dental infection

We describe a case in which recurrent vertebral osteomyelitis and psoas abscess due to Streptococcus constellatus and Fusobacterium nucleatum developed in a patient with a previously unrecognized atrial septal defect with bidirectional shunts. Disease recurrence was ascribed to the presence of dental disease, which served as the source of infection. To the best of our knowledge, this is the first case in which vertebral osteomyelitis and psoas abscess have been associated with atrial septal defect.