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PubMed1992

Pathogenicity of Fusobacterium necrophorum biovar B.

Previous studies showed that the high minimum infective dose (more than 10(6) organisms) of biovar A strains of Fusobacterium necrophorum for mice by subcutaneous inoculation could be greatly reduced, often to less than 10 organisms, by suspending the fusobacteria in sublethal doses of broth cultures of certain other bacterial species, such as Staphylococcus aureus. The present study showed that no such enhancement of infectivity occurred with two biovar B strains. This observation, together with the low pathogenicity of pure cultures of these strains for mice, suggests that biovar B plays no more than a minor role in the aetiology of necrobacillosis.

Animals↗
PubMed1986

Generation of immunity against Fusobacterium necrophorum in mice inoculated with extracts containing leucocidin.

The capacity of extracts from toxigenic and non-toxigenic ruminant strains of Fusobacterium necrophorum to protect against challenge with homologous and heterologous bacteria was examined in mice. The numbers of F. necrophorum which were infective or lethal for mice increased 5- to 8-fold in animals which had been previously inoculated with complete Freund's adjuvant (FCA). Although preparations containing lipopolysaccharide (LPS) and outer membrane proteins (OMP) from several strains gave protection against a non-toxigenic strain (FnB-3), they did not significantly immunize mice against a challenge infection with a toxigenic bovine strain, FnB-1. Only material which had been prepared by gel filtration of 18-h liquid culture supernates of toxigenic F. necrophorum elicited significant immunity against homologous challenge with FnB-1. This preparation contained LPS and the majority of the leucotoxic activity. However, passive protection was not afforded to mice inoculated with bovine or rabbit sera which possessed high neutralization titres against the leucocidin.

Animals↗
PubMed1996

An experimental ovine foot abscess model using a Fusobacterium necrophorum biotype AB.

An experimental procedure is described for the production of foot abscess in sheep that mimics the natural disease. Lesions were produced by the intradermal inoculation of suspensions of Fusobacterium necrophorum biotype AB containing from 5 x 10(2) to 5 x 10(8) bacteria, into interdigital skin devitalized by freezing with liquid nitrogen. A dose of 5 x 10(5) bacteria induced the development of foot abscess in 3 of 4 and 8 of 8 inoculated feet. It was found that to produce foot abscess in devitalized tissue required between 10(3) and 10(6) fewer bacteria than were necessary to produce similar lesions in healthy tissue.

Abscess↗
PubMed2005

Human infections with Fusobacterium necrophorum.

Fusobacterium necrophorum is a Gram-negative anaerobic bacillus that can be a primary pathogen causing either localised abscesses and throat infections or systemic life-threatening disease. Systemic infections due to F. necrophorum are referred to as either Lemierre's disease/syndrome, post-anginal sepsis or necrobacillosis, but in the context of this mini-review, all are included under the umbrella term of 'invasive F. necrophorum disease' (IFND). Although IFND has been well documented for over a century, it is quite a rare condition and modern-day clinicians of various medical disciplines are frequently unaware of this organism and the severity of symptoms that it can cause. IFND classically occurs in previously healthy young people although the factors that trigger the invasive process are not fully understood. There are countless descriptive case histories and small series of cases of IFND disease in the literature and although commonly referred to as a 'forgotten' disease, in truth, it is probably best described as a repeatedly 'discovered' disease, as it may not always be included in medical curricula, and neither is it mentioned in some major medical textbooks. There is some evidence that IFND may be on the increase, particularly in the UK. The potential reasons for this are considered in this review along with an historical overview, and updates on disease incidence, patient demography, pathogenesis and laboratory diagnosis.

Adolescent↗
PubMed2004

Orbital abscess caused by Fusobacterium necrophorum.

We report the case of previously healthy boy with orbital abscess secondary to sinusitis. Fusobacterium necrophorum and Streptococcus anginosus was cultured both from the maxillary sinus and the orbital abscess. After surgical drainage and intravenous antibiotic treatment the boy recovered without complications.

Abscess↗
PubMed2005

Enhanced pathogenicity of Fusobacterium nucleatum adapted to oxidative stress.

Fusobacterium nucleatum is an obligate anaerobic bacterium found in the indigenous human microbiota but also recovered from several anaerobic infections. Considering the biological and medical relevance of F. nucleatum, the characterization of its response to oxidative stress is needed in order to understand how this anaerobic bacterium survives during an invasive process of oxygenated tissues. Influence of oxidative stress by atmospheric oxygen exposure on cellular morphology and pathogenicity of F. nucleatum were investigated. The wild-type F. nucleatum ATCC 25586 (wt-strain) was exposed to oxidative stress to select an adapted strain (aero-strain). Conventional NIH Swiss mice were split in two experimental groups which were challenged intraperitoneally with wt-strain and aero-strain, respectively, and a control group, unchallenged. Histopathological and hyperemia analysis were performed by day 30 after infection. Gram stain of aero-strain showed drastic changes in cellular morphology when compared to wt-strain. A significant increase of liver weight/body weight ratio (P < 0.05) as well as a tendency (P = 0.16) to higher spleen weight/body weight ratio were observed for the mice challenged with aero-strain when compared to the two other animal groups. Additionally, these animals also showed hyperemia in the spleen and liver as well as an increased number of inflammatory cells and steatosis in the liver. The results showed that, in addition to extensive changes in cell morphology, the adaptation to oxidative stress might also influence the pathogenicity of F. nucleatum. These findings have clinical implications since in the host tissues this indigenous putative pathogen is exposed to more or less oxygenated environments found on the different anatomic sites invaded by the bacterium.

Adaptation, Physiological↗
PubMed2005

Efficient gene transfer and targeted mutagenesis in Fusobacterium nucleatum.

Fusobacterium nucleatum is a Gram-negative anaerobe important in dental biofilm ecology and infectious diseases with significant societal impact. The lack of efficient genetic systems has hampered molecular analyses in this microorganism. We previously reported construction of a shuttle plasmid, pHS17, using the native fusobacterial plasmid pFN1 and an erythromycin resistance cassette. However, the host range of pHS17 was restricted to F. nucleatum, ATCC 10953, and the transformation efficiency was limited. This study was undertaken to improve genetic systems for molecular analysis in F. nucleatum. We identified a second F. nucleatum strain, ATCC 23726, which is transformed with improved efficiency compared to ATCC 10953. Two novel second generation pFN1-based shuttle plasmids, pHS23 and pHS30, were developed and enable transformation of ATCC 23726 at 6.2 x 10(4) and 1.5 x 10(6) transformants/mug plasmid DNA, respectively. The transformation efficiency of pHS30, which harbors a catP gene conferring resistance to chloramphenicol, was more than 1000-fold greater than that of pHS17. The improved transformation efficiency facilitated disruption of the chromosomal rnr gene using a suicide plasmid pHS19, the first demonstration of targeted mutagenesis in F. nucleatum. These results provide significant advances in the development of systems for molecular analysis in F. nucleatum.

Chloramphenicol Resistance↗
PubMed2003

Antagonistic interactions among Fusobacterium nucleatum and Prevotella intermedia with oral lactobacilli.

Microbiota residing in oral ecosystems show great complexity because of the mutual interdependence of certain microorganisms that might influence their presence or absence at a given site. The aim of this work was to evaluate possible antagonistic interactions among Fusobacterium nucleatum and Prevotella intermedia, isolated from periodontal pockets, and Lactobacillus casei, L. salivarius, L. rhamnosus and L. plantarum isolated from saliva. Different tests were carried out using each strain as an effector as well as a sensitive strain, alternatively: (1) agar diffusion with paper disks embedded with supernatants and pellets in different culture media; (b) the well diffusion assay; (c) the double layer method; and (d) OD(560) measurements of the kinetic growth of Lactobacillus strains in LAPTg broth with different volumes of F. nucleatum supernatant. P. intermedia supernatant did not have an inhibitory effect on Lactobacillus growth, except for L. casei, when the double plaque method was used. F. nucleatum supernatant inhibited growth of all Lactobacillus strains when the well diffusion method was used. F. nucleatum inhibited L. casei growth whatever the method used. The substance responsible for inhibition was a thermoresistant extracellular protein which was hydrolyzed by trypsin-like proteases. None of the species of lactobacilli studied inhibited the growth of P. intermedia or F. nucleatum.

Antibiosis↗
PubMed2004

Antiproliferative activity of Actinobacillus (Haemophilus) actinomycetemcomitans and Fusobacterium nucleatum in peripheral blood mononuclear cells.

Several studies indicate Actinobacillus (Haemophilus) actinomycetemcomitans and Fusobacterium nucleatum as etiologic agents of periodontal disease. Immunosuppressive factors produced by microorganisms probably contribute to the initiation and evolution of this disease. This study evaluated the antiproliferative activity of ammonium precipitate fractions of A. (H.) actinomycetemcomitans and F. nucleatum isolates from humans and marmosets both with and without periodontal disease. All A. (H.) actinomycetemcomitans and most F. nucleatum strains inhibited PBMC proliferation in a dose-dependent manner. The degree of cell proliferative inhibition of each bacterial species differed among the strains and was independent of host clinical status. The in vitro inhibition of stimulated lymphocyte proliferation induced by different A. (H.) actinomycetemcomitans and F. nucleatum isolates demonstrated the importance of this phenomenon in bacterial virulence, playing a possible suppressor role in host defense mechanisms in vivo. Moreover, our findings pointed out a marked difference between A. (H.) actinomycetemcomitans and F. nucleatum cytoplasmic extracts in their antiproliferative activity, regarding the antigen concentration required for maximum inhibition and their vulnerability to heating and proteolytic treatment.

Actinobacillus Infections↗
PubMed2005

Effects of a collagenolytic cell wall component from Fusobacterium necrophorum subsp. necrophorum on rabbit tissue-culture cells.

The effects on rabbit tissue-cultured cells of collagenolytic cell wall component (CCWC) from Fusobacterium necrophorum subsp. necrophorum were investigated. Scanning electron microscopy demonstrated that CCWC damaged the cell surfaces of the rabbit granulocytes and hepatocytes but the effects of the cells differed from each other. Granulocytes appeared smooth and morphologically irregular whereas hepatocytes looked rough and had tiny holes in the cell membranes. Differences in cell viability were observed in MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulphophenyl)-2H-tetrazolium, inner salt) assay. The findings suggest that cytotoxic activity in vivo may well contribute to the establishment of an initial injury in visceral tissues, and the action of CCWC could increase the chances of survival for an invading F. necrophorum subsp. necrophorum at the first stages of infection.

Animals↗
PubMed2005

The two major subspecies of Fusobacterium necrophorum have distinct leukotoxin operon promoter regions.

Fusobacterium necrophorum, a gram-negative, non-spore-forming anaerobe, is a normal inhabitant of the alimentary tract of animals and humans. Two types of F. necrophorum, subspecies necrophorum (biotype A) and funduliforme (biotype B), have been recognized, which differ morphologically, biochemically and biologically. The organism is an opportunistic pathogen that causes numerous necrotic conditions (necrobacillosis) such as bovine hepatic abscesses and ruminant foot abscesses. Subspecies necrophorum strains are considered to be more virulent for cattle and have been shown to produce greater amounts of leukotoxin than subspecies funduliforme strains. The leukotoxin operon of F. necrophorum consists of three genes (lktBAC) of which the leukotoxin structural gene (lktA) is the second gene in the operon. In this study, the promoter regions of the leukotoxin operons from the two subspecies were identified and their nucleotide sequence compared. The promoter regions were found to differ in sequence, in length of the sequence between the upstream determinant (oppF) and the first gene of the leukotoxin operon (lktB), and in promoter strength as assayed in Escherichia coli host cells.

Animals↗
PubMed2001

Orbital cellulitis caused by Fusobacterium necrophorum.

PURPOSE: To report the case of a previously healthy young female who developed orbital cellulitis caused by Fusobacterium necrophorum. We are unaware of previous reports of this condition caused by the same anaerobic, gram-negative, nonsporeforming bacterium and could find no reference to it in a computer search using MEDLINE. METHODS: Case report. RESULTS: In the case of orbital cellulitis presented here, the patient required 3 sinus debridement operations and 30 days of intravenous antibiotics. Despite this, her vision did not fully recover. CONCLUSION: F. necrophorum is capable of causing severe orbital disease that requires aggressive and prompt treatment to preserve sight.

Adolescent↗
PubMed1992

Fusobacterium nucleatum bacteraemia with multiple liver abscesses in an HIV-I antibody positive man with IgG2 deficiency.

Liver abscess formation due to Fusobacterium nucleatum is rare. We describe an HIV-I antibody positive man, with normal surrogate markers of cell-mediated immunity, who presented with F. nucleatum bacteraemia and liver abscess formation. He was found to have IgG2 subclass deficiency. This case illustrates the clinical importance of altered B-cell function in patients who are at an early stage of HIV disease.

Adult↗
PubMed2003

Immunogenicity and protective effects of truncated recombinant leukotoxin proteins of Fusobacterium necrophorum in mice.

Fusobacterium necrophorum, a gram-negative, anaerobic and rod-shaped bacterium, is generally an opportunistic pathogen and causes a wide variety of necrotic infections in animals and humans. Leukotoxin, a secreted protein, is a major virulence factor. The gene encoding the leukotoxin (lktA) in F. necrophorum has been cloned, sequenced and expressed in Escherichia coli. Because of low expression levels, problems associated with purifying full-length recombinant protein, and of the physical instability of the protein, five overlapping leukotoxin gene truncations were constructed. The recombinant polypeptides (BSBSE, SX, GAS, SH, and FINAL) were expressed in E. coli and purified by nickel-affinity chromatography. The objectives were to investigate the effectiveness of the purified truncated polypeptides to induce protective immunity in mice challenged with F. necrophorum. The polypeptides, individually or in combination, and inactivated native leukotoxin or culture supernatant of F. necrophorum were homogenized with an adjuvant and injected into mice on days 0 and 21. Blood samples were collected to measure serum anti-leukotoxin antibody titers on days 0, 21 and 42 and on day 42, mice were experimentally challenged with F. necrophorum. All polypeptides were immunogenic, with GAS polypeptide eliciting the least antibody response. Two polypeptides (BSBSE and SH) induced significant protection in mice against F. necrophorum infection. Protection was better than the full-length native leukotoxin or inactivated supernatant.The study demonstrated that the leukotoxin of F. necrophorum carries epitopes that induce protective immunity against experimental fusobacterial infection, thus providing further evidence to the importance of leukotoxin as a major virulence factor.

Animals↗
PubMed2000

The virulence of mixed infection with Streptococcus constellatus and Fusobacterium nucleatum in a murine orofacial infection model.

Orofacial infections are usually polymicrobial, and it is the microbial interactions of pathogenic species that cause tissue destruction. In this study, the microbial interaction between Streptococcus constellatus and Fusobacterium nucleatum was characterized using a murine orofacial infection model. A mixture of viable S. constellatus and F. nucleatum cells (both 2 x 10(8) CFU/mouse) was injected into the submandible; as a result, all of the test mice died. In contrast, none of the experimental animals monoinjected with either S. constellatus or F. nucleatum died (P<0.001), indicating that the synergism between the two resulted in the virulence. When a mixture of viable S. constellatus cells and a culture filtrate of F. nucleatum was tested, lethality and the bacterial cell count per lesion were significantly enhanced as compared with monoinjections (P<0.02). However, the virulence of F. nucleatum was not enhanced by infection of a culture filtrate of S. constellatus. The enhancement of virulence was observed even when viable S. constellatus cells and the culture filtrate of F. nucleatum were injected at separate sites. Heat treatment of the culture filtrate of F. nucleatum did not affect the enhancement. These results indicate that a heat-stable substance(s) produced by F. nucleatum contributes to the microbial synergy of S. constellatus and F. nucleatum in orofacial infections.

Abscess↗
PubMed1985

The weak immunogenicity of Fusobacterium necrophorum.

Three of four extreme methods of immunization completely failed to protect mice against challenge with the homologous strain of Fusobacterium necrophorum. Unsuccessful vaccines included (1) broth culture killed by mild heat and emulsified with Freund's complete adjuvant, and (2) a homogenate of heavily infected mouse brains, inactivated by mild heat and given in two doses. Also unsuccessful as a method of immunization was the production of a severe subcutaneous infection with F. necrophorum, followed by curative treatment with metronidazole. Slight but significant protection against subcutaneous challenge resulted, however, from two such infections given in rapid succession. It would appear that the main virulence factors of F. necrophorum are only weakly immunogenic, and the experiments give little encouragement to the prospect of an effective necrobacillosis vaccine.

Animals↗
PubMed1984

The pathogenic properties of Fusobacterium and Bacteroides species from wallabies and other sources.

Intracerebral inoculation was more effective than intraperitoneal, intravenous or subcutaneous inoculation as a means of producing lethal infections with Fusobacterium necrophorum in mice. Strains varied in virulence but, of five examined, two had LD50 values as low as ca. 8000 and 14000 viable organisms. Profuse bacterial multiplication in the brain was demonstrated. Intravenous vaccination with a single large dose of heat-killed whole culture or washed bacterial cells failed to protect against intracerebral challenge. Intracerebral injection of other fusobacteria (F. nucleatum, F. varium and F. necrogenes) and of 22 strains belonging to 10 Bacteroides spp. was without apparent effect on mice, except for a slight transient illness in some animals given B. fragilis. This organism (five strains) differed from the other Bacteroides spp. tested, which included eight strains belonging to the fragilis group, in being eliminated more slowly from the mouse brain--a point that may be relevant to the special pathogenicity of B. fragilis in endogenous infections in man. There was no evidence that B. fragilis multiplied in the brain or that intravenous vaccination with a large dose of heat-killed homologous culture affected the rate at which it was eliminated.

Animals↗