New medium selective for Fusobacterium species and differential for Fusobacterium necrophorum

Profiling Fusobacterium infection at high taxonomic resolution reveals lineage-specific correlations in colorectal cancer

The bacterial genus Fusobacterium promotes colorectal cancer (CRC) development, but an understanding of its precise composition at the species level in the human gut and the relevant association with CRC is lacking. Herein, we devise a Fusobacterium rpoB amplicon sequencing (FrpoB-seq) method that enables the differentiation of Fusobacterium species and certain subspecies in the microbiota. By applying this method to clinical tissue and faecal samples from CRC patients, we detect 62 Fusobacterium species, including 45 that were previously undescribed. We additionally reveal that Fusobacterium species may display different lineage-dependent functions in CRC. Specifically, a lineage (designated L1) including F. nucleatum, F. hwasookii, F. periodonticum and their relatives (rather than any particular species alone) is overabundant in tumour samples and faeces from CRC patients, whereas a non-enriched lineage (designated L5) represented by F. varium and F. ulcerans in tumours has a positive association with lymphovascular invasion.

Bacteria from the genus Fusobacterium can promote colorectal cancer (CRC) development; however, the exact Fusobacterium species involved in this process remain underexplored. Here, the authors develop a rpoB amplicon sequencing approach to identify Fusobacterium species and subspecies in CRC patient samples.

Isolation and identification of Dichelobacter nodosus and Fusobacterium necrophorum using the polymerase chain reaction method in sheep with footrot

Footrot is an important infectious disease of small ruminants leading to severe economical losses. The aim of the present study was to determine isolation and identification rates ofDichelobacter nodosusandFusobacterium necrophorumin the culture techniques and reveal the specificity and sensitivity of the culture technique based on the polymerase chain reaction (PCR) method in sheep with footrot. Dry swabs and swabs with Amies medium from 83 sheep were subjected to PCR and culture analyses. In dry swabs, 4 samples were positive forF. necrophorumand all were negative forD. nodosus. Colonies in Eugon and Fusobacterium selective agars from swabs with Amies medium were evaluated. Polymerase chain reaction analysis was conducted on macroscopically and microscopically unidentified samples. The positivity rate was 55.4% forD. nodosusand 69.8% forF. necrophorumin cultures from Fusobacterium selective agars. The positivity rate forD. nodosusin Fusobacterium selective agars was higher than that in Eugon agar. Performing PCR and culture methods increased positivity as compared to performing them alone. In comparison with the PCR method, culturing in Fusobacterium selective agars had moderate sensitivity and low specificity forD. nodosus(71.7 and 28.7%) andF. necrophorum(61.3 and 80.0%), respectively. In conclusion, Fusobacterium selective agar (without antibiotics) for isolation and identification ofD. nodosusis superior to Eugon agar.Fusobacterium necrophorumshould also be considered as a provoking agent for footrot in small ruminants. The PCR method on culture increases elucidation of definitive aetiology.

Laboratory maintenance of fusobacteria

This unit describes routine laboratory handling of fusobacteria. Different media that can be used to grow or enrich Fusobacterium nucleatum and other species of this genus are described. The growth and stock conditions as well as the susceptibility of F. nucleatum to oxygen in a pure culture are also discussed.

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.

Inulin, oligofructose and intestinal function

Inulin and oligofructose have attracted much attention recently as nonabsorbable carbohydrates with prebiotic properties. When inulin and oligofructose were added to a controlled diet, significant increases were noted in colonic bifidobacterial populations, and it has been proposed that these changes promote both colonic and systemic health through modification of the intestinal microflora. Inulin and oligofructose are rapidly and completely fermented by the colonic microflora with the production of acetate and other short-chain fatty acids. As with lactulose, they may also result in the growth of the fecal biomass, and in doing so, entrap ammonia for bacterial protein synthesis or conversion to the ammonium ion. As with dietary fiber and other nonabsorbable carbohydrates, there is also interest in inulin and oligofructose from the standpoint of inhibition of colonic carcinogenesis, blood cholesterol reduction, immune stimulation and enhanced vitamin synthesis. In these areas, the influence of their molecular weight is also an issue, with the longer chain length providing a more sustained fermentation pattern. More human studies are now required, including studies on the long-term effects of inulin and oligofructose consumption on colonic health, in particular on markers of cancer risk such as reduction in colonic polyp recurrence.

Colonic bacterial activity and serum lipid risk factors for cardiovascular disease

Antibiotics are being proposed for the treatment of cardiovascular disease. In the past, antibiotics were advocated for the control of hypercholesterolemia. We have therefore investigated the relation between colonic bacterial activity and serum lipids. In a four-phase randomized crossover study, we fed a different starch supplement during each 2-week phase to 24 healthy subjects. In two phases, supplements containing resistant starches were fed that reach the colon and are largely fermented by colonic bacteria. Fecal starch recovery therefore reflects the metabolic activity of colonic microflora. The control treatments were conventional starches. Blood lipid levels were obtained at the start and 4-day fecal collections at the end of each phase. Resistant starch supplements increased fecal starch excretion by 3.8 +/- 1.2 g/d more than conventional starches (P = .006). Mean starch excretion was related positively to pretreatment serum high-density lipoprotein (HDL) cholesterol (r = -.57, P = .003) and negatively to low-density lipoprotein (LDL) cholesterol (r = -.57, P = .004), apolipoprotein B:AI (r = -.56, P = .005), and fecal output of fusobacteria (r = -.73, P = .003) and bacteroides (r = -.72, P = .003). The ratio of fusobacteria to total anaerobes was also related to pretreatment LDL cholesterol (r = .56, P = .037). Differences in starch excretion between healthy subjects, as a measure of bacterial activity, accounted for 32% of the variation in pretreatment LDL cholesterol. The activity of colonic microflora therefore appears to influence serum lipid levels. Alterations of bacterial number and activity may provide an additional strategy to control serum lipid risk factors for cardiovascular disease.

Aetiology of ovine footrot in Spain

Four hundred and sixty strains of obligate anaerobes were isolated from 216 cases of ovine foot rot distributed throughout Spain. The predominant species was Dichelobacter nodosus, which was isolated in 168 cases (77.8 per cent). A higher proportion of the strains of D nodosus than of the other strains had elastolytic activity, 118 of the 168 strains degrading elastin. Species belonging to the genus Prevotella were isolated from 96 cases (44.4 per cent). Serotyping of the D nodosus strains showed that serovars A1, A2 and C were the most commonly isolated in Spain.

Microbiological features of gingivitis in pubertal children

The subgingival microflora of 42 pubertal children (aged 12-15 years) and 18 young adults (aged 21-25 years) was investigated by anaerobic culture and phase contrast microscopy. Motile rods, spirochetes and Prevotella intermedia were elevated proportionately in pubertal children with gingivitis (median GI > or = 1); however, no statistically significant differences in enumerated organisms on selective media were observed between pubertal children and young adults. These organisms were positively correlated with the index of bleeding on probing and the gingival index of pubertal children. Pubertal children were divided into 3 distinct subject clusters according to the similarity of subgingival microbial features, and the subjects who were then selected for the gingivitis group were distributed into clusters 1 and 2. The proportions of motile rods, P. intermedia and Eikenella corrodens were significantly higher in cluster 2 than in cluster 1. These results suggest that these 2 species and motile rods which differentiated features of clusters, are useful for screening of high-risk subjects for worsening of inflammation.

Selective enumeration of Fusobacterium necrophorum from the bovine rumen

A culture medium containing lactate as the sole energy source and antibiotics (bacitracin, gentamicin, and streptomycin) was used for selection and enumeration of Fusobacterium necrophorum from bovine ruminal contents. F. necrophorum growth was determined by indole production, and enumeration was performed by the most-probable-number technique. The number of F. necrophorum cells in cattle fed a 100% forage diet was 7 x 10(5)/g of ruminal contents. The number increased (P < 0.05) 10-fold after the diet was changed to 85% corn grain.

Cellular fatty acids in Fusobacterium species as a tool for identification

Identification of fusobacteria from clinical specimens currently requires analysis of metabolic end products by gas-liquid chromatography in addition to certain biochemical and enzymatic tests because of the relative biochemical inactivity of these bacteria. Even the finding of pointed, thin gram-negative cells on Gram-stained slides can no longer be relied on for identification of Fusobacterium nucleatum, since at least four other species of fusobacteria have been seen to exhibit similar morphology. We examined 46 clinical isolates and six American Type Culture Collection type strains of fusobacteria by conventional methods and by the Microbial ID Systems MIDI software package for analyzing cellular fatty acid patterns measured by capillary column gas-liquid chromatography. Distinctive patterns of major fatty acids could be used to reliably identify most clinical isolates to the species level. The MIDI system identified 89% of the isolates correctly and provides an alternative to conventional methods.

A selective medium for Fusobacterium spp

A new selective medium (JVN) for the isolation of Fusobacterium spp. from clinical material is described. The medium incorporates josamycin, vancomycin and norfloxacin (at 3, 4 and 1 microgram/ml, respectively) as the selective agents, plus 5% defibrinated horse blood in Fastidious Anaerobe Agar Base (Lab M). This formula allowed luxuriant growth of all 82 strains (eight recognized species) of fusobacteria tested, while significantly inhibiting 51/51 (100%) strains of facultative anaerobes and 45/51 (88%) strains of other obligate anaerobes. JVN medium allowed the successful isolation of strains of Fusobacterium naviforme, F. nucleatum and F. necrophorum from the gingivae of 9/16 healthy volunteers, and strains of F. varium and F. mortiferum from faecal suspensions seeded with these organisms.

Obligately anaerobic bacterial species isolated from foot-rot lesions in goats

Lesions showing clinical signs of foot-rot from 120 goats were cultured on six selective media during October 1987 to November 1988. A total of 582 strictly anaerobic microorganisms belonging to 50 different species was isolated and identified. The anaerobes most frequently isolated belonged to the following genera: Bacteroides (80%), Peptostreptococcus (63.6%), Megasphaera (40%), Fusobacterium (29.2%), Clostridium (22.5%), Propionibacterium (12.5%), Eubacterium (11.7%) and Leptotrichia (10.8%). Percentages for Acidaminococcus, Peptococcus, Tissierella, Wolinella and Veillonella were below 10%. The following species were identified in 10% or more of cases: Peptostreptococcus anaerobius (61.7%), Bacteroides buccae (51.7%), Bacteroides nodosus (42.5%), Megasphaera elsdenii (40%), Bacteroides ruminicola subsp. brevis (22.5%), Fusobacterium necrophorum (19.2%), Leptotrichia buccalis (11.7%) and Clostridium perfringens (10%). Lower percentages were obtained for the remaining species. The efficiency and selectivity of the six culture media used for isolation are discussed.

Selective medium for isolation of Bacteroides gracilis

A new medium selective for Bacteroides gracilis was developed. The medium is tryptic soy agar (Difco Laboratories, Detroit, Mich.) containing nalidixic acid, teicoplanin, sodium formate, sodium fumarate, and potassium nitrate. All 18 strains of B. gracilis tested grew with only minimal inhibition. Most of the other 214 organisms tested, including most Bacteroides species, other anaerobes, and a substantial number of facultative anaerobes, were significantly inhibited by the medium. In a diagnostic study of 49 clinical specimens (28 patients with intra-abdominal infection, mostly gangrenous or perforated appendicitis), four strains of B. gracilis were isolated (from 4 different patients) on B. gracilis selective agar but were not detected on standard media.

The microbiology of HIV-associated periodontal lesions

2 intraoral lesions associated with human immunodeficiency virus (HIV) infection have recently been described: an atypical gingivitis and a rapidly progressive periodontitis. The microbiota associated with these gingival and periodontal lesions was investigated. Subgingival plaque samples were taken from 45 HIV-seropositive homosexual men and from 44 HIV-seronegative control subjects. Each sampled site was clinically and radiographically classified as HIV-associated gingivitis, HIV-associated periodontitis, healthy in an HIV-seropositive subject, or healthy, conventional gingivitis or classical periodontitis in a control subject. Plaque samples were examined by indirect immunofluorescence with polyclonal antisera to detect Bacteroides gingivalis, B. intermedius, Fusobacterium nucleatum, and Actinobacillus actinomycetemcomitans. Anaerobic culturing was used to detect black-pigmented Bacteroides species, Fusobacterium species, and A. actinomycetemcomitans to confirm the immunofluorescence findings. We detected B. gingivalis, B. intermedius, F. nucleatum, and A. actinomycetemcomitans in significantly more HIV-periodontitis sites (80, 65, 59 and 61% of sites, respectively) and HIV-gingivitis sites (61, 70, 52 and 52%, respectively) than in HIV-seropositive healthy and control sites (p less than 0.05). The results indicate that the microbiota found in HIV-periodontitis is similar to that of classical periodontitis. In contrast, however, the microbiota associated with HIV-gingivitis is strikingly different from that of conventional gingivitis. The similarity in the prevalence of periodontopathic organisms in both HIV-gingivitis and HIV-periodontitis suggests that the HIV-gingivitis lesion may be a precursor to the tissue destruction observed in HIV-periodontitis. Hence, early detection and treatment of the HIV-gingivitis lesion may prevent the rapid and extensive breakdown of periodontal tissues associated with HIV-periodontitis.

Prevalence and microbiology of localized prepubertal periodontitis

Loss of crestal alveolar bone at primary teeth was ascertained radiographically in a dental school clinical population of 2264 children. 19 patients (0.84%) demonstrated distinct periodontal bone destruction around one or more primary teeth; in only 2 of these patients had periodontal disease been identified in previous clinical examinations. A microbiological study of 35 subgingival samples from 9 available patients revealed a high prevalence of black-pigmented Bacteroides spp., mainly Bacteroides intermedius. Actinobacillus actinomycetemcomitans and Capnocytophaga spp. were predominant organisms in some samples. The present data indicate that localized prepubertal periodontitis is more common than previously realized and is associated with bacteria generally regarded as major periodontal pathogens.

Clinical and microbiologic effects of single-dose metronidazole or scaling and root planing in treatment of adult periodontitis

Sites affected with adult periodontitis were observed for 3 months to compare their clinical and microbiologic responses to a single 2 g dose of metronidazole, scaling and root planing, or no treatment. 2 sites with probing depths greater than or equal to 5 mm in each of 18 female subjects (6 in each treatment group) were evaluated clinically (plaque and bleeding indices, probing depth, attachment loss) and microbiologically (%s of cocci, motile rods, non-motile rods and spirochetes, and of obligate anaerobic colony-forming units, black-pigmented Bacteroides, Fusobacterium and Actinobacillus actinomycetemcomitans in subgingival plaque). No significant differences in these variables existed between the 3 groups at baseline. The no-treatment (control) group showed no substantial clinical or microbiologic changes during the study. After 1 month, scaling and root planing had effected significant clinical improvement and significant shifts in the subgingival flora to a pattern more consistent with periodontal health; these changes were still evident at 3 months. In contrast, 1 month after metronidazole, there was some clinical improvement and a significant increase in cocci and a decrease in motile rods, but at 3 months these changes were no longer evident. The results show that the benefits of scaling and root planing are sustained for at least 3 months. However, the benefits of a single 2 g dose of metronidazole are both few and transient, indicating that this regimen, while effective against anaerobic infections in other organ systems, is not clinically or microbiologically effective in the treatment of adult periodontitis.

Identification of fusobacteria in a routine diagnostic laboratory

A scheme for differentiating Fusobacterium spp. and Leptotrichia spp. from Bacteroides spp. was devised after examining 114 strains of fusobacteria and asaccharolytic bacteroides (17 reference strains and 97 clinical isolates). Sensitivity to a 300 micrograms/ml plate of phosphomycin and an acid reaction on a lysine plate were found to be reliable for differentiating Fusobacterium spp. and L. buccalis from Bacteroides. Using a short set of simple cultural and biochemical tests, isolates could be identified as F. necrophorum, F. necrogenes, F. nucleatum, F. varium or L. buccalis. These tests were: indole, lecithinase, phosphatase, DNase and gas production, aesculin and casein hydrolysis, greening of casein/methylene blue agar, nitrite reduction, bile tolerance and haemolysis on horse blood agar.