Bacteroides Distasonis Research Articles

The Beta-Lactam Resistome Expressed by Aerobic and Anaerobic Bacteria Isolated from Human Feces of Healthy Donors.

Antibiotic resistance is a major health problem worldwide, causing more deaths than diabetes and cancer. The dissemination of vertical and horizontal antibiotic resistance genes has been conducted for a selection of pan-resistant bacteria. Here, we test if the aerobic and anaerobic bacteria from human feces samples in health conditions are carriers of beta-lactamases genes. The samples were cultured in a brain–heart infusion medium and subcultured in blood agar in aerobic and anaerobic conditions for 24 h at 37 °C. The grown colonies were identified by their biochemical profiles. The DNA was extracted and purified by bacterial lysis using thermal shock and were used in the endpoint PCR and next generation sequencing to identify beta-lactamase genes expression (OXA, VIM, SHV, TEM, IMP, ROB, KPC, CMY, DHA, P, CFX, LAP, and BIL). The aerobic bacterias Aeromonas hydrophila, Citrobacter freundii, Proteus mirabilis, Providencia rettgeri, Serratia fonticola, Serratia liquefaciens, Enterobacter aerogenes, Escherichia coli, Klebsiella pneumoniae, Pantoea agglomerans, Enterococcus faecalis, and Enterobacter cloacae, the anaerobic bacteria: Capnocytophaga species, Bacteroides distasonis, Bifidobacterium adolescentis, Bacteroides ovatus, Bacteroides fragilis, Eubacterium species, Eubacterium aerofaciens, Peptostreptococcus anaerobius, Fusobacterium species, Bacteroides species, and Bacteroides vulgatus were isolated and identified. The results showed 49 strains resistant to beta-lactam with the expression of blaSHV (10.2%), blaTEM (100%), blaKPC (10.2%), blaCYM (14.3%), blaP (2%), blaCFX (8.2%), and blaBIL (6.1%). These data support the idea that the human enteric microbiota constitutes an important reservoir of genes for resistance to beta-lactamases and that such genes could be transferred to pathogenic bacteria.

Sex and strain dependent differences in mucosal immunology and microbiota composition in mice

BackgroundA dysbiosis in the intestinal microbiome plays a role in the pathogenesis of several immunological diseases. These diseases often show a sex bias, suggesting sex differences in immune responses and in the intestinal microbiome. We hypothesized that sex differences in immune responses are associated with sex differences in microbiota composition.MethodsFecal microbiota composition (MITchip), mRNA expression in intestinal tissue (microarray), and immune cell populations in mesenteric lymph nodes (MLNs) were studied in male and female mice of two mouse strains (C57B1/6OlaHsd and Balb/cOlaHsd). Transcriptomics and microbiota data were combined to identify bacterial species which may potentially be related to sex-specific differences in intestinal immune related genes.ResultsWe found clear sex differences in intestinal microbiota species, diversity, and richness in healthy mice. However, the nature of the sex effects appeared to be determined by the mouse strain as different bacterial species were enriched in males and females of the two strains. For example, Lactobacillus plantarum and Bacteroides distasonis were enriched in B6 females as compared to B6 males, while Bifidobacterium was enriched BALB/c females as compared to BALB/c males. The strain-dependent sex effects were also observed in the expression of immunological genes in the colon. We found that the abundance of various bacteria (e.g., Clostridium leptum et rel.) which were enriched in B6 females positively correlated with the expression of several genes (e.g., Il-2rb, Ccr3, and Cd80) which could be related to immunological functions, such as inflammatory responses and migration of leukocytes. The abundance of several bacteria (e.g., Faecalibacterium prausnitzii et rel. and Coprobacillus et rel.- Clostridium ramosum et rel.) which were enriched in BALB/c males positively correlated to the expression of several genes (e.g., Apoe, Il-1b, and Stat4) related to several immunological functions, such as proliferation and quantity of lymphocytes. The net result was the same, since both mouse strains showed similar sex induced differences in immune cell populations in the MLNs.ConclusionsOur data suggests a correlation between microbiota and intestinal immune populations in a sex and strain-specific way. These findings may contribute to the development of more sex and genetic specific treatments for intestinal-related disorders.

Application of quantitative real-time PCR for rapid identification of Bacteroides fragilis group and related organisms in human wound samples

Our goal was to establish a quantitative real-time PCR (QRT-PCR) method to detect Bacteroides fragilis group and related organisms from clinical specimens. Compared to conventional anaerobic culture, QRT-PCR can provide accurate and more rapid detection and identification of B. fragilis group and similar species. B. fragilis group and related organisms are the most frequently isolated anaerobic pathogens from clinical samples. However, culture and phenotypic identification is quite time-consuming. We designed specific primers and probes based on the 16S rRNA gene sequences of Bacteroides caccae, Bacteroides eggerthii, B. fragilis, Bacteroides ovatus, Bacteroides stercoris, Bacteroides thetaiotaomicron, Bacteroides uniformis, Bacteroides vulgatus, Odoribacter splanchnicus ( Bacteroides splanchnicus), Parabacteroides distasonis ( Bacteroides distasonis) and Parabacteroides merdae ( Bacteroides merdae), and detected these species by means of QRT-PCR in 400 human surgical wound infection samples or closed abscesses. The target bacteria were detected from 31 samples (8%) by culture, but from 132 samples (33%) by QRT-PCR ( p-value < 0.001). B. uniformis was the most common species (44 positive samples) according to QRT-PCR while culture showed it to be B. fragilis (16 positive samples). Additionally, for each species QRT-PCR detected higher counts than culture did; this may reflect detecting DNA of dead organisms by QRT-PCR. QRT-PCR is a rapid and sensitive method which has great potential for detection of B. fragilis group and related organisms in wound samples.

Epizootic rabbit enteropathy inoculum (TEC4): antibiograms and antibiotic fractionation

Epizootic rabbit enteropathy (ERE) emerged and spread in Europe within the last 13years causing major economical loss. The aims of the study was to evaluate antibiograms of TEC4, an inoculum composed of an extract of intestinal content of affected rabbits, and to test the potential of different antibiotic-based TEC4 fractions to reproduce the disease. Twenty nine different antibiotic discs were incubated for determining bacteria resistance. In a complementary study, nine tubes of liquid medium were inoculated with TEC4, incubated and added individually with amoxicillin/clavulanic acid, bacitracin, ceftiofur, doxycycline, novobiocin, streptomycyin, tylosin, vancomycin and 0.9% saline solution as control. The content of each tube was washed by centrifugation and suspended in saline. The three most effective antibiotics are florfenicol, amoxycillin/clavulanic acid and tylosin. A high concentration of Clostridium sordelli and Bacillus firmus were isolated in all fractions. Species never cultured from TEC4 were identified as Fusobacterium necrogenes (in vancomycin fraction), Cellulomonas sp (in novobiocin fraction) and Bacteroides distasonis (in doxycycline fraction). The ERE was reproduced when bacitracin, doxycycline and 0.9% fractions were inoculated. Rabbits showed ERE clinical signs with the specific drop in daily weight gain.

Intestinal Bacteroides species associated with coeliac disease

AimsTo characterise the predominant species of bacterial populations associated with duodenal biopsies of paediatric patients with active and treated coeliac disease.Methods20 biopsy specimens from patients with active coeliac disease, 12...

Abstract 1957: Loss of TGFβ1 alters host-microbial interactions, predisposing the colonic epithelium to inflammation

Abstract Introduction: The TGFB pathway is mutated in up to 30% of human colon cancers. Genetically Engineered Mouse Models (GEMs) with deficient TGFβ signaling model several characteristics of IBD associated human colon cancers. Introduction of Helicobacter sp. into the Tgfb1−/−Rag2−/− mouse model is necessary for the development of inflammatory lesions which progress to adenoma and carcinoma. The exact role of TGFβ1 and bacterial-associated inflammation has yet to be elucidated and offers a potential target for the prevention of colon cancer. Methods: To determine the function of TGFβ1 on colonic bacterial composition we used GEM models, Tgfb1−/−Rag2−/− and Tgfb1+/+Rag2−/−. The cecal microflora of 10 Tgfb1−/−Rag2−/− and 10 Tgfb1+/+Rag2−/− mice were isolated and serially diluted onto brucella (BRU), bacteroides bile esculin (BBE), and laked kanomycin-vancomycin (LKV) media under anaerobic conditions. Colony forming units (CFUs) were enumerated. Individual colony types were then streaked onto trypitcase soy agar with 5% sheep blood and grown anaerobically and aerobically. The bacteria were then gram-stained and biotyped utilizing a Dade Berhing MicroScan instrument. To further examine the bacterial composition we designed primers specific to the 16s rRNA subunit of different Bacteroides species, and using the Roche LightCycler preformed quantitative Real Time-PCR (qRT-PCR) on fecal DNA. Results: The Dade Berhing Instrument showed that Tgfb1−/−Rag2−/− mice had a 4 fold increase in bacterial load and a 28 fold increase in Bacteroides species when compared with Tgfb1+/+Rag2−/− mice. The qRT-PCR results showed an increase in Bacteroides fragilis and Bacteroides distasonis and a significant decrease in Bacteroides thetaiotaomicron in the Tgfb1−/−Rag2−/− mice. These data suggest that loss of TGFβ1 alters the colonic microflora. Previous studies illustrated the importance of bacterial nutrient sources on bacterial composition. To examine if TGFβ1 is altering nutrient availability in the colon a previous micro-array was analyzed for candidate genes associated with glycoprotein metabolism. This showed changes in fucose metabolizing enzymes with the loss of TGFβ1. Conclusion: These findings suggest that TGFβ1 plays a role in bacterial load maintenance, possibly by altering available nutrient sources and when disrupted, can cause abnormalities in pathobionts (commensal bacterial with pathogenic potential) which could then lead to increased inflammation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1957.

Lessons Learned from the Anaerobe Survey: Historical Perspective and Review of the Most Recent Data (2005–2007)

The rationale and lessons learned through the evolution of the National Survey for the Susceptibility of Bacteroides fragilis Group from its initiation in 1981 through 2007 are reviewed here. The survey was conceived in 1980 to track emerging antimicrobial resistance in Bacteroides species. Data from the last 11 years of the survey (1997-2007), including 6574 isolates from 13 medical centers, were analyzed for in vitro antimicrobial resistance to both frequently used and newly developed anti-anaerobic agents. The minimum inhibitory concentrations of the antibiotics were determined using agar dilution in accordance with Clinical and Laboratory Standards Institute recommendations. The analyses revealed that the carbapenems (imipenem, meropenem, ertapenem, and doripenem) and piperacillin-tazobactam were the most active agents against these pathogens, with resistance rates of 0.9%-2.3%. In the most recent 3 years of the survey (2005-2007), resistance to some agents was shown to depend on the species, such as ampicillin-sulbactam against Bacteroides distasonis (20.6%) and tigecycline against Bacteroides uniformis and Bacteroides eggerthii ( approximately 7%). Very high resistance rates (>50%) were noted for moxifloxacin and trovafloxacin, particularly against Bacteroides vulgatus. During that period of study, non-B. fragilis Bacteroides species had >40% resistance to clindamycin. Metronidazole-resistant Bacteroides strains were also first reported during that period. In summary, resistance to antibiotics was greater among non-B. fragilis Bacteroides species than among B. fragilis and was especially greater among species with a low frequency of isolation, such as Bacteroides caccae and B. uniformis. The emergence of resistance among the non-B. fragilis Bacteroides species underscores the need for speciation of B. fragilis group isolates and for clinicians to be aware of associations between species and drug resistance.

The Bioavailability of Apigenin-7-Glucoside Is Influenced by Human Intestinal Microbiota in Rats

We investigated the impact of human intestinal microbiota on bioavailability of the flavone apigenin-7-glucoside (A7G) by comparing germ-free and human microbiota-associated (HMA) rats. First, the ability of the human intestinal microbiota to convert A7G was proven in vitro by incubating A7G with fecal suspensions. Apigenin, naringenin, and 3-(4-hydroxyphenyl)propionic acid were formed as main metabolites. After application of A7G to germ-free rats, apigenin, luteolin, and their conjugates were detected in urine and feces. In HMA rats, naringenin, eriodictyol, phloretin, 3-(3,4-dihydroxyphenyl)propionic acid, 3-(4-hydroxyphenyl)propionic acid, 3-(3-hydroxyphenyl)propionic acid, and 4-hydroxycinnamic acid in their free and conjugated forms were additionally formed. In whole-blood samples from germ-free and HMA rats, only apigenin conjugates and phloretin, respectively, were detected. The total excretion of A7G and its metabolites within 48 h was similarly low in both germ-free and HMA rats, with 11 and 13% of the A7G dose, respectively. In germ-free rats, A7G metabolites dominated by apigenin and its conjugates were mainly excreted with feces. In contrast, the compounds in HMA rats were predominantly recovered from urine, 3-(4-hydroxyphenyl)propionic acid being the main metabolite. The ability of selected gut bacteria and the host intestinal mucosa to deglycosylate A7G was tested using cell extracts. Apigenin was formed by cytosolic extracts of Eubacterium ramulus and Bacteroides distasonis and by the microsomal fraction of the small intestinal mucosa of rats. Overall, human intestinal microbiota largely contributed to A7G metabolism, indicating its influence on the bioactivity of flavones.

Bioactivation of Selenocysteine Derivatiives by β-Lyases Present in Common Gastrointestinal Bacterial Species

Studies in cell cultures and animal models have demonstrated cancer chemopreventive effects of certain selenium compounds. Here we describe the screening of cysteine S-conjugate beta-lyase activity in bacterial species that are implicated in the bio-activation of sulfur- and selenocysteine derivatives. We screened a range of bacterial species commonly found in the human intestine for beta-lyase activity on Se-p-methoxybenzylselenocysteine and the natural occurring S-methylcysteine and Se-methylselenocysteine conjugates. A high-performance liquid chromatography (HPLC)-assisted assay was established to determine specific activities of each strain. Of the 29 tested bacterial species, 22 showed specific activities towards the test compound reaching up to 10.1 U/mg protein, thereby accounting for 75% of total fecal activity (13.3. U/mg protein). Lysates of four bacterial strains (Bacteroides distasonis, bacteroides vulgatus, Enterococcus faecalis, and Enterococcus faecium), which exhibited high specific activities towards the test compound and which are known to be present at high numbers in the human intestine, were characterized further. Our results indicate that beta-lyase activity is widely distributed in human intestinal bacteria and might play a key role in the bioactivation of selenocysteine derivatives.

&lt;i&gt;Bacteroides (Parabacteroides) distasonis&lt;/i&gt; Splenic Abscess in a Sickle Cell Patient

Splenic abscess is not an uncommon complication of patients with sickle-cell disease. Here we describe an 18 year-old boy with sickle cell disease and left upper quadrant abdominal pain. Computerized axial tomography revealed left sided free flowing pleural effusion and splenomegaly with liquefaction and possible gas formation. The splenic fluid grew an unusual organism known as Bacteroides distasonis. The patient received antimicrobial therapy and underwent a splenectomy with full recovery. The spleen was cystically infarcted and measured 22 x 16 x 5 cm. The capsule was thickened and covered by fibrinous exudate. Histopathologic examination of the spleen showed complete necrosis with reparative fibrosis. This case presents an unusual cause of splenic abscess due to Bacteroides distasonis with a subacute to chronic course. The presence of fever and left sided pleuritic chest pain in patients with sickle cell disease should raise the suspicion of splenic abscess.

Segmented filamentous bacteria in a defined bacterial cocktail induce intestinal inflammation in SCID mice reconstituted with CD45RBhigh CD4+ T cells

The aim was to analyze the influence of intestinal microbiota on the development of intestinal inflammation. We used the model of chronic inflammation that develops spontaneously in the colon of conventional severe combined immunodeficiency (SCID) mice restored with the CD45 RB(high) subset of CD4+T cells isolated from the spleen of normal BALB/c mice. A CD4+CD45RB(high) subpopulation of T cells was purified from the spleen of conventional BALB/c mice by magnetic separation (MACS) and transferred into immunodeficient SCID mice. Germ-free (GF) SCID mice or SCID mice monoassociated with Enterococcus faecalis, SFB (segmented filamentous bacteria), Fusobacterium mortiferum, Bacteroides distasonis, and in combination Fusobacterium mortiferum + SFB or Bacteroides distasonis + SFB were used as recipients. SCID mice were colonized by a defined cocktail of specific pathogen-free (SPF) bacteria. Mice were evaluated 8-12 weeks after the cell transfer for clinical and morphological signs of inflammatory bowel disease (IBD). After the transfer of the CD4+CD45RB(high) T-cell subpopulation to SCID mice severe colitis was present in conventional animals and in mice colonized with a cocktail of SPF microflora plus SFB. Altered intestinal barrier in the terminal ileum of mice with severe colitis was documented by immunohistology using antibodies to ZO-1 (zona occludens). Only SFB bacteria together with a defined SPF mixture were effective in triggering intestinal inflammation in the model of IBD in reconstituted SCID mice, while no colitis was detected in GF mice or in mice colonized either with SPF microflora or monoassociated only with SFB or colonized by Bacteroides distasonis + SFB or Fusobacterium mortiferum + SFB.

Evolution of Symbiotic Bacteria in the Distal Human Intestine

The adult human intestine contains trillions of bacteria, representing hundreds of species and thousands of subspecies. Little is known about the selective pressures that have shaped and are shaping this community's component species, which are dominated by members of the Bacteroidetes and Firmicutes divisions. To examine how the intestinal environment affects microbial genome evolution, we have sequenced the genomes of two members of the normal distal human gut microbiota, Bacteroides vulgatus and Bacteroides distasonis, and by comparison with the few other sequenced gut and non-gut Bacteroidetes, analyzed their niche and habitat adaptations. The results show that lateral gene transfer, mobile elements, and gene amplification have played important roles in affecting the ability of gut-dwelling Bacteroidetes to vary their cell surface, sense their environment, and harvest nutrient resources present in the distal intestine. Our findings show that these processes have been a driving force in the adaptation of Bacteroidetes to the distal gut environment, and emphasize the importance of considering the evolution of humans from an additional perspective, namely the evolution of our microbiomes.

Identification of Commensal Bacterial Strains That Modulate Yersinia enterocolitica and Dextran Sodium Sulfate-Induced Inflammatory Responses: Implications for the Development of Probiotics

An increasing body of evidence suggests that probiotic bacteria are effective in the treatment of enteric infections, although the molecular basis of this activity remains elusive. To identify putative probiotics, we tested commensal bacteria in terms of their toxicity, invasiveness, inhibition of Yersinia-induced inflammation in vitro and in vivo, and modulation of dextran sodium sulfate (DSS)-induced colitis in mice. The commensal bacteria Escherichia coli, Bifidobacterium adolescentis, Bacteroides vulgatus, Bacteroides distasonis, and Streptococcus salivarius were screened for adhesion to, invasion of, and toxicity for host epithelial cells (EC), and the strains were tested for their ability to inhibit Y. enterocolitica-induced NF-kappaB activation. Additionally, B. adolescentis was administered to mice orally infected with Y. enterocolitica and to mice with mucosae impaired by DSS treatment. None of the commensal bacteria tested was toxic for or invaded the EC. B. adolescentis, B. distasonis, B. vulgatus, and S. salivarius inhibited the Y. enterocolitica-induced NF-kappaB activation and interleukin-8 production in EC. In line with these findings, B. adolescentis-fed mice had significantly lower results for mean pathogen burden in the visceral organs, intestinal tumor necrosis factor alpha mRNA expression, and loss of body weight upon oral infection with Y. enterocolitica. In addition, the administration of B. adolescentis decelerated inflammation upon DSS treatment in mice. We suggest that our approach might help to identify new probiotics to be used for the treatment of inflammatory and infectious gastrointestinal disorders.

Association Between the cfxA Gene and Transposon Tn4555 in Bacteroides distasonis Strains and Other Bacteroides Species

The Bacteroides genus, the most prevalent anaerobic bacteria of the intestinal tract, carries a plethora of the mobile elements, such as plasmids and conjugative and mobilizable transposons, which are probably responsible for the spreading of resistance genes. Production of beta-lactamases is the most important resistance mechanism including cephalosporin resistance to beta-lactam agents in species of the Bacteroides fragilis group. In our previous study, the cfxA gene was detected in B. distasonis species, which encodes a clinically significant broad-spectrum beta-lactamase responsible for widespread resistance to cefoxitin and other beta-lactams. Such gene has been associated with the mobilizable transposon Tn4555. Therefore, the aim of this study was to detect the association between the cfxA gene and the presence of transposon Tn4555 in 53 Bacteroides strains isolated in Rio de Janeiro, Brazil, by PCR assay. The cfxA gene was detected in 11 strains and the Tn4555 in 15. The transposon sequence revealed similarities of approximately 96% with the B. vulgatus sequence which has been deposited in GenBank. Hybridization assay was performed in attempt to detect the cfxA gene in the transposon. It was possible to associate the cfxA gene in 11 of 15 strains that harbored Tn4555. Among such strains, 9 presented the cfxA gene as well as Tn4555, but in 2 strains the cfxA gene was not detected by PCR assay. Our results confirm the involvement of Tn4555 in spreading the cfxA gene in Bacteroides species.

Luminex detection of fecal indicators in river samples, marine recreational water, and beach sand

Research to understand and remediate coastal pollution is moving toward a multitiered approach in which traditional enumeration of fecal indicators is accompanied by molecular analysis of a variety of targets. Technology that rapidly detects multiple microbial contaminants would benefit from such an approach. The Luminex ® 100™ system is a suspension array that assays multiple analytes rapidly in a single well of a microtiter plate. The ability of the system to simultaneously detect multiple fecal indicating bacteria in environmental samples was tested. Primer/probe sets were designed to simultaneously detect the following fecal indicators: the Bacteroides fragilis group, Enterococcus spp., Escherichia coli and Shigella spp., Bacteroides distasonis, and Ent. faecalis. Specificity and sensitivity of the Luminex probes was tested against laboratory cultures. In addition, sequencing, culture plate testing, and specificity testing with environmental isolates were steps taken to validate the function of the assay with environmental samples. Luminex response to cultures and to environmental samples was consistent with sequencing results, suggesting that the technology has the potential to simultaneously detect multiple targets for coastal water quality applications, particularly as progress is made to efficiently extract DNA from water and sediment matrices.

Antianaerobe activity of ceftobiprole, a new broad-spectrum cephalosporin

Agar dilution testing of 463 anaerobes showed most Gram-positive β-lactamase–negative strains (other than some Clostridium difficile and Peptostreptococcus anaerobius), as well as both β-lactamase–positive and β-lactamase–negative strains of Fusobacterium nucleatum, to have ceftobiprole MIC values of ≤0.016 to 4 μg/mL. Ceftobiprole was less active against β-lactamase–positive Gram-negative bacilli, especially the members of the Bacteroides fragilis group. Like ceftobiprole, piperacillin was active mainly against β-lactamase–negative strains, though MIC values for piperacillin were often 1 to 2 dilutions higher than for ceftobiprole. Carbapenems had MIC values ≤4 μg/L against all except some C. difficile and 2 strains of B. fragilis. All strains were susceptible to metronidazole, and all bacteria, except C. difficile and a single Bacteroides distasonis strain, were susceptible to chloramphenicol. Clindamycin resistance was seen in most anaerobe groups, whereas high moxifloxacin MICs were found mainly among the B. fragilis and Prevotella groups, and a few C. difficile and F. nucleatum strains.

RNA polymerase β-subunit gene (rpoB) sequence analysis for the identification of Bacteroides spp.

Partial rpoB sequences (317 bp) of 11 species of Bacteroides, two Porphyromonas spp. and two Prevotella spp. were compared to delineate the genetic relationships among Bacteroides and closely related anaerobic species. The high level of inter-species sequence dissimilarities (7.6-20.8%) allowed the various Bacteroides spp. to be distinguished. The position of the Bacteroides distasonis and Bacteriodes merdae cluster in the rpoB tree was different from the position in the 16S rRNA gene tree. Based on rpoB sequence similarity and clustering in the rpoB tree, it was possible to correctly re-identify 80 clinical isolates of Bacteroides. In addition to two subgroups, cfiA-negative (division I) and cfiA-positive (division II), of Bacteroides fragilis isolates, two distinct subgroups were also found among Bacteroides ovatus and Bacteroides thetaiotaomicron isolates. Bacteroides genus-specific rpoB PCR and B. fragilis species-specific rpoB PCR allowed Bacteroides spp. to be differentiated from Porphyromonas and Prevotella spp., and also allowed B. fragilis to be differentiated from other non-fragilisBacteroides spp. included in the present study.

Mutagenicity of arbutin in mammalian cells after activation by human intestinal bacteria

Arbutin (hydroquinone-β-D-glucopyranoside) is present in various food plants. Its aglycone, hydroquinone, is mutagenic and carcinogenic. We investigated whether hydroquinone may be released under conditions encountered in the human gastrointestinal tract. Arbutin was stable in artificial gastric juice. Fecal slurries from nine human subjects completely converted arbutin (2 mM) into hydroquinone. Four of nine representative human intestinal species investigated, namely Eubacterium ramulus, Enterococcus casseliflavus, Bacteroides distasonis, and Bifidobacterium adolescentis, deglycosylated arbutin at rates of 21.08, 16.62, 8.43 and 3.59 nmol × min −1 × (mg protein) −1, respectively. In contrast, homogenates from small intestinal mucosa and cytosolic fractions from colon mucosa deglycosylated arbutin at substantially lower rates: 0.50 and 0.09 nmol × min −1 × (mg protein) −1, respectively. Arbutin, unlike hydroquinone, did not induce gene mutations in Chinese hamster V79 cells in the absence of an activating system. However, in the presence of cytosolic fractions from E. ramulus or B. distasonis, arbutin was strongly mutagenic. Cytosolic fraction from Escherichia coli, showing no arbutin glycosidase activity, was not able to activate arbutin in this model system. The release of the proximate mutagen hydroquinone from arbutin by intestinal bacteria in the immediate vicinity of the colon mucosa may pose a potential risk.

Reclassification of Bacteroides distasonis, Bacteroides goldsteinii and Bacteroides merdae as Parabacteroides distasonis gen. nov., comb. nov., Parabacteroides goldsteinii comb. nov. and Parabacteroides merdae comb. nov.

The characteristics of three Bacteroides species, Bacteroides distasonis, Bacteroides goldsteinii and Bacteroides merdae, were examined. 16S rRNA gene sequence analysis showed that B. distasonis, B. goldsteinii and B. merdae should not be classified as species within the genus Bacteroides. Although B. distasonis, B. goldsteinii and B. merdae were phylogenetically related to Tannerella forsythensis, the ratios of anteiso-C(15 : 0) to iso-C(15 : 0) in whole-cell methanolysates of the three species were different from that of T. forsythensis. In addition, whereas the major menaquinones of T. forsythensis were MK-10 and MK-11, the major menaquinones of B. distasonis, B. goldsteinii and B. merdae were MK-9 and MK-10. The three species were phenotypically similar to Bacteroides sensu stricto, but phylogenetically distinct. Furthermore, B. distasonis, B. goldsteinii and B. merdae could be differentiated from Bacteroides sensu stricto (predominant menaquinones: MK-10 and MK-11) by the menaquinone composition. This is an important chemotaxonomic characteristic of the three species. On the basis of these data, a novel genus, Parabacteroides gen. nov., is proposed for B. distasonis, B. goldsteinii and B. merdae, with three species, Parabacteroides distasonis gen. nov., comb. nov. (the type species), Parabacteroides goldsteinii comb. nov. and Parabacteroides merdae comb. nov. The type strains of P. distasonis, P. goldsteinii and P. merdae are JCM 5825(T) (=CCUG 4941(T)=DSM 20701(T)=ATCC 8503(T)), JCM 13446(T) (=CCUG 48944(T)) and JCM 9497(T) (=CCUG 38734(T)=ATCC 43184(T)), respectively.

Phylogeny of human intestinal bacteria that activate the dietary lignan secoisolariciresinol diglucoside

The human intestinal microbiota is essential for the conversion of the dietary lignan secoisolariciresinol diglucoside (SDG) via secoisolariciresinol (SECO) to the enterolignans enterodiol (ED) and enterolactone (EL). However, knowledge of the species that catalyse the underlying reactions is scant. Therefore, we focused our attention on the identification of intestinal bacteria involved in the conversion of SDG. Strains of Bacteroides distasonis, Bacteroides fragilis, Bacteroides ovatus and Clostridium cocleatum, as well as the newly isolated strain Clostridium sp. SDG-Mt85-3Db, deglycosylated SDG. Demethylation of SECO was catalysed by strains of Butyribacterium methylotrophicum, Eubacterium callanderi, Eubacterium limosum and Peptostreptococcus productus. Dehydroxylation of SECO was catalysed by strains of Clostridium scindens and Eggerthella lenta. Finally, the newly isolated strain ED-Mt61/PYG-s6 catalysed the dehydrogenation of ED to EL. The results indicate that the activation of SDG involves phylogenetically diverse bacteria, most of which are members of the dominant human intestinal microbiota.