Publications by authors named "Martin Iain Bahl"

40 Publications

Acute Experimental Barrier Injury Triggers Ulcerative Colitis-Specific Innate Hyperresponsiveness and Ulcerative Colitis-Type Microbiome Changes in Humans.

Cell Mol Gastroenterol Hepatol 2021 Jun 9. Epub 2021 Jun 9.

Department of Gastroenterology, Herlev Hospital, University of Copenhagen, Copenhagen, Denmark.

Background And Aims: The trigger hypothesis opens the possibility of anti-flare initiation therapies by stating that ulcerative colitis (UC) flares originate from inadequate responses to acute mucosal injuries. However, experimental evidence is restricted by a limited use of suitable human models. We thus aimed to investigate the acute mucosal barrier injury responses in humans with and without UC using an experimental injury model.

Methods: A standardized mucosal break was inflicted in the sigmoid colon of 19 patients with UC in endoscopic and histological remission and 20 control subjects. Postinjury responses were assessed repeatedly by high-resolution imaging and sampling to perform Geboes scoring, RNA sequencing, and injury niche microbiota 16S ribosomal RNA gene sequencing.

Results: UC patients had more severe endoscopic postinjury inflammation than did control subjects (P < .01), an elevated modified Geboes score (P < .05), a rapid induction of innate response gene sets (P < .05) and antimicrobial peptides (P < .01), and engagement of neutrophils (P < .01). Innate lymphoid cell type 3 (ILC3) markers were increased preinjury (P < .01), and ILC3 activating cytokines were highly induced postinjury, resulting in an increase in ILC3-type cytokine interleukin-17A. Across groups, the postinjury mucosal microbiome had higher bacterial load (P < .0001) and lower α-diversity (P < .05).

Conclusions: UC patients in remission respond to mucosal breaks by an innate hyperresponse engaging resident regulatory ILC3s and a subsequent adaptive activation. The postinjury inflammatory bowel disease-like microbiota diversity decrease is irrespective of diagnosis, suggesting that the dysbiosis is secondary to host injury responses. We provide a model for the study of flare initiation in the search for antitrigger-directed therapies.
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http://dx.doi.org/10.1016/j.jcmgh.2021.06.002DOI Listing
June 2021

Determining Gut Microbial Dysbiosis: a Review of Applied Indexes for Assessment of Intestinal Microbiota Imbalances.

Appl Environ Microbiol 2021 05 11;87(11). Epub 2021 May 11.

National Food Institute, Technical University of Denmark, Kgs Lyngby, Denmark

Assessing "dysbiosis" in intestinal microbial communities is increasingly considered a routine analysis in microbiota studies, and it has added relevant information to the prediction and characterization of diseases and other adverse conditions. However, dysbiosis is not a well-defined condition. A variety of different dysbiosis indexes have been suggested and applied, but their underlying methodologies, as well as the cohorts and conditions for which they have been developed, differ considerably. To date, no comprehensive overview and comparison of all the different methodologies and applications of such indexes is available. Here, we list all types of dysbiosis indexes identified in the literature, introduce their methodology, group them into categories, and discuss their potential descriptive and clinical applications as well as their limitations. Thus, our focus is not on the implications of dysbiosis for disease but on the methodological approaches available to determine and quantify this condition.
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http://dx.doi.org/10.1128/AEM.00395-21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8208139PMC
May 2021

Gut Microbiota Perturbation in IgA Deficiency Is Influenced by IgA-Autoantibody Status.

Gastroenterology 2021 Jun 1;160(7):2423-2434.e5. Epub 2021 Mar 1.

Division of Clinical Immunology, Department of Laboratory Medicine, Karolinska Institutet at Karolinska University Hospital, Huddinge, Stockholm, Sweden. Electronic address:

Background & Aims: IgA exerts its primary function at mucosal surfaces, where it binds microbial antigens to regulate bacterial growth and epithelial attachment. One third of individuals with IgA deficiency (IgAD) suffers from recurrent mucosal infections, possibly related to an altered microbiota. We aimed to delineate the impact of IgAD and the IgA-autoantibody status on the composition and functional capacity of the gut microbiota.

Methods: We performed a paired, lifestyle-balanced analysis of the effect of IgA on the gut microbiota composition and functionality based on fecal samples from individuals with IgAD and IgA-sufficient household members (n = 100), involving quantitative shotgun metagenomics, species-centric functional annotation of gut bacteria, and strain-level analyses. We supplemented the data set with 32 individuals with IgAD and examined the influence of IgA-autoantibody status on the composition and functionality of the gut microbiota.

Results: The gut microbiota of individuals with IgAD exhibited decreased richness and diversity and was enriched for bacterial species encoding pathogen-related functions including multidrug and antimicrobial peptide resistance, virulence factors, and type III and VI secretion systems. These functional changes were largely attributed to Escherichia coli but were independent of E coli strain variations and most prominent in individuals with IgAD with IgA-specific autoreactive antibodies.

Conclusions: The microbiota of individuals with IgAD is enriched for species holding increased proinflammatory potential, thereby potentially decreasing the resistance to gut barrier-perturbing events. This phenotype is especially pronounced in individuals with IgAD with IgA-specific autoreactive antibodies, thus warranting a screening for IgA-specific autoreactive antibodies in IgAD to identify patients with IgAD with increased risk for gastrointestinal implications.
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http://dx.doi.org/10.1053/j.gastro.2021.02.053DOI Listing
June 2021

Settlers of our inner surface - Factors shaping the gut microbiota from birth to toddlerhood.

FEMS Microbiol Rev 2021 Jan 11. Epub 2021 Jan 11.

National Food Institute, Technical University of Denmark, DK-2800 Kgs. Lyngby.

During the first three years of life, the microbial ecosystem within the human gut undergoes a process that is unlike what happens in this ecosystem at any other time of our life. This period in time is considered a highly important developmental window, where the gut microbiota is much less resilient and much more responsive to external and environmental factors than seen in the adult gut. While advanced bioinformatics and clinical correlation studies have received extensive focus within studies of the human microbiome, basic microbial growth physiology has attracted much less attention, although it plays a pivotal role to understand the developing gut microbiota during early life. In this review, we will thus take a microbial ecology perspective on the analysis of factors that influence the temporal development of the infant gut microbiota. Such factors include sources of microbes that seed the intestinal environment, physico-chemical (abiotic) conditions influencing microbial growth, and the availability of nutrients needed by the intestinal microbes.
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http://dx.doi.org/10.1093/femsre/fuab001DOI Listing
January 2021

The microbiota of farmed mink (Neovison vison) follows a successional development and is affected by early life antibiotic exposure.

Sci Rep 2020 11 24;10(1):20434. Epub 2020 Nov 24.

Department of Veterinary Clinical and Animal Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg C, Denmark.

On many mink farms, antibiotics are used extensively during the lactation period to reduce the prevalence and severity of pre-weaning diarrhoea (PWD) in mink kits (also referred to as greasy kit syndrome). Concerns have been raised, that routine treatment of PWD with antibiotics could affect the natural successional development of the gut microbiota, which may have long lasting consequences. Here we investigated the effects of early life antibiotic treatment administered for 1 week (postnatal days 13-20). Two routes of antibiotic administration were compared to a non-treated control group (CTR, n = 24). Routes of administration included indirect treatment, through the milk from dams receiving antibiotics by intramuscular administration (ABX_D, n = 24) and direct treatment by intramuscular administration to the kits (ABX_K, n = 24). A tendency for slightly increased weight at termination (Day 205) was observed in the ABX_K group. The gut microbiota composition was profiled by 16S rRNA gene sequencing at eight time points between Day 7 and Day 205. A clear successional development of the gut microbiota composition was observed and both treatment regimens caused detectable changes in the gut microbiota until at least eight days after treatment ceased. At termination, a significant positive correlation was identified between microbial diversity and animal weight.
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http://dx.doi.org/10.1038/s41598-020-77417-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7686315PMC
November 2020

Faecal microbiota transplantation for eradication of co-infection with and extensively drug-resistant KPC-producing .

Scand J Gastroenterol 2020 May 23;55(5):626-630. Epub 2020 Apr 23.

Department of Hepatology and Gastroenterology, Aarhus University Hospital, Aarhus, Denmark.

infection may be complicated by co-infection with other pathogens. We here describe the successful use of faecal microbiota transplantation to eradicate concomitant and extensively drug-resistant (XDR) KPC-producing Donor microbiota efficiently engrafted in the patient, and a donor-like microbial assemblage persisted in the patient during six months follow-up. The report explores the potential for the donor microbiota to eradicate and replace multi-resistant microorganisms.
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http://dx.doi.org/10.1080/00365521.2020.1753806DOI Listing
May 2020

Short-Term Amoxicillin-Induced Perturbation of the Gut Microbiota Promotes Acute Intestinal Immune Regulation in Brown Norway Rats.

Front Microbiol 2020 26;11:496. Epub 2020 Mar 26.

National Food Institute, Technical University of Denmark, Kongens Lyngby, Denmark.

The intestinal gut microbiota is essential for maintaining host health. Concerns have been raised about the possible connection between antibiotic use, causing microbiota disturbances, and the increase in allergic and autoimmune diseases observed during the last decades. To elucidate the putative connection between antibiotic use and immune regulation, we have assessed the effects of the antibiotic amoxicillin on immune regulation, protein uptake, and bacterial community structure in a Brown Norway rat model. Daily intra-gastric administration of amoxicillin resulted in an immediate and dramatic shift in fecal microbiota, characterized by a reduction of within sample (α) diversity, reduced variation between animals (β diversity), increased relative abundance of Bacteroidetes and Gammaproteobacteria, with concurrent reduction of Firmicutes, compared to a water control group. In the small intestine, amoxicillin also affected microbiota composition significantly, but in a different way than observed in feces. The small intestine of control animals was vastly dominated by , but this genus was much less abundant in the amoxicillin group. Instead, multiple different genera expanded after amoxicillin administration, with high variation between individual animals, thus the small intestinal α and β diversity were higher in the amoxicillin group compared to controls. After 1 week of daily amoxicillin administration, total fecal IgA level, relative abundance of small intestinal regulatory T cells and goblet cell numbers were higher in the amoxicillin group compared to controls. Several bacterial genera, including , (Gammaproteobacteria), and , for which the relative abundance was higher in the small intestine in the amoxicillin group than in controls, were positively correlated with the fraction of small intestinal regulatory T cells. Despite of epidemiologic studies showing an association between early life antibiotic consumption and later prevalence of inflammatory bowel diseases and food allergies, our findings surprisingly indicated that amoxicillin-induced perturbation of the gut microbiota promotes acute immune regulation. We speculate that the observed increase in relative abundance of small intestinal regulatory T cells is partly mediated by immunomodulatory lipopolysaccharides derived from outgrowth of Gammaproteobacteria.
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http://dx.doi.org/10.3389/fmicb.2020.00496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7135894PMC
March 2020

Intestinal Enterococcus abundance correlates inversely with excessive weight gain and increased plasma leptin in breastfed infants.

FEMS Microbiol Ecol 2020 05;96(5)

National Food Institute, Technical University of Denmark, Kemitorvet 202, 2800 Kgs Lyngby, Denmark.

Epidemiological evidence indicates that breastfeeding provides protection against development of overweight/obesity. Nonetheless, a small subgroup of infants undergo excessive weight gain during exclusive breastfeeding, a phenomenon that remains unexplained. Breast milk contains both gut-seeding microbes and substrates for microbial growth in the gut of infants, and a large body of evidence suggests a role for gut microbes in host metabolism. Based on the recently established SKOT III cohort, we investigated the role of the infant gut microbiota in excessive infant weight gain during breastfeeding, including 30 exclusively breastfed infants, 13 of which exhibited excessive weight gain and 17 controls which exhibited normal weight gain during infancy. Infants undergoing excessive weight gain during breastfeeding had a reduced abundance of gut Enterococcus as compared with that observed in the controls. Within the complete cohort, Enterococcus abundance correlated inversely with age/gender-adjusted body-weight, body-mass index and waist circumference, body fat and levels of plasma leptin. The reduced abundance of Enterococcus in infants with excessive weight gain was coupled to a lower content of Enterococcus in breast milk samples of their mothers than seen for mothers in the control group. Together, this suggests that lack of breast milk-derived gut-seeding Enterococci may contribute to excessive weight gain in breastfed infants.
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http://dx.doi.org/10.1093/femsec/fiaa066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7183236PMC
May 2020

Banking feces: a new frontier for public blood banks?

Transfusion 2019 09 26;59(9):2776-2782. Epub 2019 Jun 26.

Department of Clinical Immunology, Aarhus University Hospital, Aarhus, Denmark.

Fecal microbiota transplantation (FMT) is an effective treatment for recurrent Clostridioides difficile infection and is potentially beneficial in other microbiota-related disorders. The provision of FMT in routine clinical practice requires an extensive infrastructure that is reliant on voluntary donors. Alongside an increasing demand for FMT, the logistic barriers of a large-scale donor-dependent operation and the difficulties among health authorities to regulate FMT limit the dissemination of sustainable FMT services. Blood centers are large organizations that handle a multitude of donor-dependent operations on a daily basis. Blood and feces share many of the same dependencies, and feces may present a new opportunity for the blood services to handle. In this paper, we describe how an FMT service may be established and embedded within the blood service infrastructure, and we explain the benefits of using blood donors as feces donors. We further explore the current indications of FMT, the challenges related to the lack of legislation, and the future perspectives for blood banks to meet a new and increasing demand.
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http://dx.doi.org/10.1111/trf.15422DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6852397PMC
September 2019

Bacterial community analysis for investigating bacterial transfer from tonsils to the pig carcass.

Int J Food Microbiol 2019 Apr 4;295:8-18. Epub 2019 Feb 4.

Technical University of Denmark, National Food Institute, Kemitorvet, Building 202, DK-2800 Kgs. Lyngby, Denmark. Electronic address:

Tonsils in the oral cavity are an important source of contamination during pig slaughter, but have not received as much attention as faecal contamination. In the present study, ten pigs were sampled from tonsils, faeces and three different areas on each carcass. The samples were analysed by both culturing of Escherichia coli and Yersinia enterocolitica and by 16S rRNA gene sequencing to characterize the bacterial communities. Comparing culture data from deep tonsil tissue and tonsil surface showed similar numbers of E. coli but significantly higher numbers of Y. enterocolitica in the deep tissue samples. Microbiota analysis showed similar bacterial communities in the two sample types at phylum level, while comparison at genus level showed significant differences between the relative abundance of several genera in the two sample types. The finding of a significantly higher relative abundance of Yersinia in tonsil tissue compared to tonsil surface supported the culture analysis. The microbiota analysis also investigated characteristics of the bacterial community that could discriminate bacterial transfer from tonsils and faeces to the carcass during slaughter. The microbiota analyses demonstrated that Fusobacteria and Proteobacteria are the most abundant phyla in tonsils, while Firmicutes showed the highest relative abundance in faeces. The dominating phylum on carcasses was Proteobacteria. Besides Proteobacteria, the swabbing area on the forepart of the carcass, showed a higher relative abundance of Firmicutes and Fusobacteria compared to swabbing areas on the rear part and mid-section of the carcass. Principal coordinate analysis showed clear clustering of samples based on sample source (tonsils, faeces and carcass). Carcass swab samples from the forepart tended to cluster closer to the tonsil samples compared to carcass swab samples from the rear part and mid-section. Identification of the genera Fusobacterium, Moraxella, Actinobacillus and non-E. coli genera of the family Enterobacteriaceae in carcass swabs could indicate tonsil contamination, while faecal contamination would more likely include higher prevalence of bacteria belonging to the class of Clostridia. The present study supports that it is possible to identify bacterial groups that are indicative for either tonsil or faecal carcass contamination. The level and composition of Enterobacteriaceae on the carcasses did, however, indicate that other sources of meat contamination than tonsils and faeces may be important, such as the process environment.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2019.02.003DOI Listing
April 2019

Antibiotic treatment of rat dams affects bacterial colonization and causes decreased weight gain in pups.

Commun Biol 2018 13;1:145. Epub 2018 Sep 13.

National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Kgs. Lyngby, Denmark.

Intergenerational transmission of bacteria during birth initiates the natural successional development of the intestinal microbiota in mammals. This process can be disrupted by antibiotic exposure, potentially affecting early-life microbiota-dependent metabolic programming. In the present study, we specifically investigate the metabolic consequences of exposing neonate Wistar rats to an antibiotic-perturbed low-diversity microbiota from birth until weaning, without exposing the pups directly to antibiotics. Here, we show that pups born from both amoxicillin and vancomycin-treated dams gain less weight than controls. This was concordant with lower feed intake as well as increased colonic expression of the PYY satiety hormone gene at weaning. The weight difference persists into adulthood even though the initial differences in gut microbiota subsided. Our results demonstrate that early-life exposure to an antibiotic-perturbed low-diversity microbiota is sufficient to cause changes in body weight persisting into adulthood.
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http://dx.doi.org/10.1038/s42003-018-0140-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6137057PMC
September 2018

Exposure to a glyphosate-based herbicide formulation, but not glyphosate alone, has only minor effects on adult rat testis.

Reprod Toxicol 2018 12 27;82:25-31. Epub 2018 Sep 27.

Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark. Electronic address:

Glyphosate has been suggested to be an endocrine disrupting chemical capable of disrupting male reproduction. There are conflicting data, however, with studies reporting effects from exposure to either glyphosate alone or to herbicide formulations, making comparisons difficult. We assessed rat testis histopathology and androgen function following two weeks exposure to either glyphosate at 2.5 and 25 mg/kg bw/day (5x and 50x Acceptable Daily Intake, ADI, respectively), or equivalent high dose of glyphosate in a herbicide formulation; Glyfonova. We observed no significant effects on testes or testosterone synthesis in rats exposed to glyphosate. Limited effects were observed in rats exposed to Glyfonova, with a small upregulation of the steroidogenic genes Cyp11a1 and Cyp17a1. We conclude that glyphosate alone has no effect on adult rat testis at exposure levels up to 25 mg/kg bw/day. Glyfonova induced only minor effects on steroidogenic gene expression, likely caused by additives other than glyphosate.
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http://dx.doi.org/10.1016/j.reprotox.2018.09.008DOI Listing
December 2018

Differential bacterial capture and transport preferences facilitate co-growth on dietary xylan in the human gut.

Nat Microbiol 2018 05 2;3(5):570-580. Epub 2018 Apr 2.

Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark.

Metabolism of dietary glycans is pivotal in shaping the human gut microbiota. However, the mechanisms that promote competition for glycans among gut commensals remain unclear. Roseburia intestinalis, an abundant butyrate-producing Firmicute, is a key degrader of the major dietary fibre xylan. Despite the association of this taxon to a healthy microbiota, insight is lacking into its glycan utilization machinery. Here, we investigate the apparatus that confers R. intestinalis growth on different xylans. R. intestinalis displays a large cell-attached modular xylanase that promotes multivalent and dynamic association to xylan via four xylan-binding modules. This xylanase operates in concert with an ATP-binding cassette transporter to mediate breakdown and selective internalization of xylan fragments. The transport protein of R. intestinalis prefers oligomers of 4-5 xylosyl units, whereas the counterpart from a model xylan-degrading Bacteroides commensal targets larger ligands. Although R. intestinalis and the Bacteroides competitor co-grew in a mixed culture on xylan, R. intestinalis dominated on the preferred transport substrate xylotetraose. These findings highlight the differentiation of capture and transport preferences as a possible strategy to facilitate co-growth on abundant dietary fibres and may offer a unique route to manipulate the microbiota based on glycan transport preferences in therapeutic interventions to boost distinct taxa.
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http://dx.doi.org/10.1038/s41564-018-0132-8DOI Listing
May 2018

Gut Colonization Is Accelerated by Presence of Older Siblings.

mSphere 2017 Nov-Dec;2(6). Epub 2017 Nov 29.

National Food Institute, Technical University of Denmark, Lyngby, Denmark.

is a highly abundant human gut microbe in healthy individuals, but it is present at reduced levels in individuals with gastrointestinal inflammatory diseases. It has therefore been suggested to constitute a marker of a healthy gut and is associated with anti-inflammatory properties. However, factors affecting the colonization of in the human gut during early life are very poorly understood. By analysis of 16S rRNA amplicon sequencing data from three separate infant study populations, we determined the colonization dynamics of and factors affecting its establishment in the gut. We found that in particular, the presence of older siblings was consistently associated with gut colonization during late infancy and conclude that acquisition of is very likely to be accelerated through transfer between siblings. has been suggested to constitute a key marker of a healthy gut, yet the factors shaping the colonization of this highly oxygen-sensitive, non-spore-forming species in the intestinal environment remain poorly understood. Here, we provide evidence from three separate infant study populations that colonization in the gut happens during late infancy and is affected by the number of older siblings in the family. We conclude that acquisition is highly likely to be accelerated by contact between siblings. Bearing in mind the immunoregulatory properties of and the well-established protective effects against allergic disorders related to the presence of older siblings, early colonization of this species may have profound consequences for child health.
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http://dx.doi.org/10.1128/mSphere.00448-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5705805PMC
November 2017

Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial.

Gut 2019 01 1;68(1):83-93. Epub 2017 Nov 1.

The Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark.

Objective: To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality.

Design: 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week dietary intervention periods comprising whole grain diet and refined grain diet, separated by a washout period of ≥6 weeks. The response to the interventions on the gut microbiome composition and insulin sensitivity as well on measures of glucose and lipid metabolism, gut functionality, inflammatory markers, anthropometry and urine metabolomics were assessed.

Results: 50 participants completed both periods with a whole grain intake of 179±50 g/day and 13±10 g/day in the whole grain and refined grain period, respectively. Compliance was confirmed by a difference in plasma alkylresorcinols (p<0.0001). Compared with refined grain, whole grain did not significantly alter glucose homeostasis and did not induce major changes in the faecal microbiome. Also, breath hydrogen levels, plasma short-chain fatty acids, intestinal integrity and intestinal transit time were not affected. The whole grain diet did, however, compared with the refined grain diet, decrease body weight (p<0.0001), serum inflammatory markers, interleukin (IL)-6 (p=0.009) and C-reactive protein (p=0.003). The reduction in body weight was consistent with a reduction in energy intake, and IL-6 reduction was associated with the amount of whole grain consumed, in particular with intake of rye.

Conclusion: Compared with refined grain diet, whole grain diet did not alter insulin sensitivity and gut microbiome but reduced body weight and systemic low-grade inflammation.

Trial Registration Number: NCT01731366; Results.
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http://dx.doi.org/10.1136/gutjnl-2017-314786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839833PMC
January 2019

Glyphosate has limited short-term effects on commensal bacterial community composition in the gut environment due to sufficient aromatic amino acid levels.

Environ Pollut 2018 Feb 5;233:364-376. Epub 2017 Nov 5.

National Food Institute, Technical University of Denmark, Kgs. Lyngby, Denmark. Electronic address:

Recently, concerns have been raised that residues of glyphosate-based herbicides may interfere with the homeostasis of the intestinal bacterial community and thereby affect the health of humans or animals. The biochemical pathway for aromatic amino acid synthesis (Shikimate pathway), which is specifically inhibited by glyphosate, is shared by plants and numerous bacterial species. Several in vitro studies have shown that various groups of intestinal bacteria may be differently affected by glyphosate. Here, we present results from an animal exposure trial combining deep 16S rRNA gene sequencing of the bacterial community with liquid chromatography mass spectrometry (LC-MS) based metabolic profiling of aromatic amino acids and their downstream metabolites. We found that glyphosate as well as the commercial formulation Glyfonova450 PLUS administered at up to fifty times the established European Acceptable Daily Intake (ADI = 0.5 mg/kg body weight) had very limited effects on bacterial community composition in Sprague Dawley rats during a two-week exposure trial. The effect of glyphosate on prototrophic bacterial growth was highly dependent on the availability of aromatic amino acids, suggesting that the observed limited effect on bacterial composition was due to the presence of sufficient amounts of aromatic amino acids in the intestinal environment. A strong correlation was observed between intestinal concentrations of glyphosate and intestinal pH, which may partly be explained by an observed reduction in acetic acid produced by the gut bacteria. We conclude that sufficient intestinal levels of aromatic amino acids provided by the diet alleviates the need for bacterial synthesis of aromatic amino acids and thus prevents an antimicrobial effect of glyphosate in vivo. It is however possible that the situation is different in cases of human malnutrition or in production animals.
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http://dx.doi.org/10.1016/j.envpol.2017.10.016DOI Listing
February 2018

Short-term effect of oral amoxicillin treatment on the gut microbial community composition in farm mink (Neovison vison).

FEMS Microbiol Ecol 2017 07;93(7)

National Food Institute, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.

It is well documented that antibiotics have pronounced modulatory effects on the intestinal bacterial community of both humans and animals, with potential health consequences. The gut microbiota of mink has however attracted little attention due to low bacterial load and fast gastrointestinal transit time, questioning its relevance. In this study, we hypothesise that oral amoxicillin treatment affects the gut microbiota in mink. This was investigated in a controlled trial including 24 animals of which 12 were treated with amoxicillin for 7 days. By applying 16S rRNA gene sequencing, we found that the faecal microbiota was markedly altered already after 2 days of treatment, with a surprising increase in diversity to resemble the feed. The diversity within the mucosa at termination was however reduced, which indicates this compartment as an important colonisation site in mink. No impact on blood biochemistry, lipid metabolism, serum amyloid A, vitamins A and E and histomorphology of the gut and liver was found; however, a slight decrease in fat digestibility was observed. We suggest that early-life use of amoxicillin in mink production may be counteractive as dysbiosis of the microbiota during infancy is increasingly being recognised as a risk factor for future health.
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http://dx.doi.org/10.1093/femsec/fix092DOI Listing
July 2017

Administration of two probiotic strains during early childhood does not affect the endogenous gut microbiota composition despite probiotic proliferation.

BMC Microbiol 2017 Aug 17;17(1):175. Epub 2017 Aug 17.

National Food Institute, Technical University of Denmark, Kemitorvet, DK-2800, Lyngby, Denmark.

Background: Probiotics are increasingly applied to prevent and treat a range of infectious, immune related and gastrointestinal diseases. Despite this, the mechanisms behind the putative effects of probiotics are poorly understood. One of the suggested modes of probiotic action is modulation of the endogenous gut microbiota, however probiotic intervention studies in adults have failed to show significant effects on gut microbiota composition. The gut microbiota of young children is known to be unstable and more responsive to external factors than that of adults. Therefore, potential effects of probiotic intervention on gut microbiota may be easier detectable in early life. We thus investigated the effects of a 6 month placebo-controlled probiotic intervention with Bifidobacterium animalis subsp. lactis (BB-12®) and Lactobacillus rhamnosus (LGG®) on gut microbiota composition and diversity in more than 200 Danish infants (N = 290 enrolled; N = 201 all samples analyzed), as assessed by 16S rRNA amplicon sequencing. Further, we evaluated probiotic presence and proliferation by use of specific quantitative polymerase chain reaction (qPCR).

Results: Probiotic administration did not significantly alter gut microbiota community structure or diversity as compared to placebo. The probiotic strains were detected in 91.3% of the fecal samples from children receiving probiotics and in 1% of the placebo treated children. Baseline gut microbiota was not found to predict the ability of probiotics to establish in the gut after the 6 month intervention. Within the probiotics group, proliferation of the strains LGG® and BB-12® in the gut was detected in 44.7% and 83.5% of the participants, respectively. A sub-analysis of the gut microbiota including only individuals with detected growth of the probiotics LGG® or BB-12® and comparing these to placebo revealed no differences in community structure or diversity.

Conclusion: Six months of probiotic administration during early life did not change gut microbiota community structure or diversity, despite active proliferation of the administered probiotic strains. Therefore, alteration of the healthy infant gut microbiota is not likely to be a prominent mechanism by which these specific probiotics works to exert beneficial effects on host health.

Trial Registration: NCT02180581 . Registered 30 June 2014.
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http://dx.doi.org/10.1186/s12866-017-1090-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5561568PMC
August 2017

Abortion and mortality in farm mink (Neovison vison) associated with feed-born Clostridium limosum.

Vet Microbiol 2017 May 18;203:229-233. Epub 2017 Mar 18.

National Food Institute, Technical University of Denmark, 2860, Søborg, Denmark.

Disease in mink clinically characterized by abortion and increased mortality among pregnant female mink on 28 Danish farms was observed during April and May 2015. Most of these farms suffered extensive disease problems, including a significant increase in the number of mated females without litters. Pathological, microbiological and molecular biological methods were applied to investigate the cause of disease. Necropsies of animals found dead revealed fragile and partially dissolved (liquefying) uterine tissue, with the presence of Gram positive rod-shaped bacteria. These slow growing bacteria were isolated by anaerobic culturing and identified as Clostridium limosum by both MALDI-TOF mass spectrometry analysis and 16S rRNA gene sequencing. All the performed tests for relevant differential diagnoses were negative. Foodborne disease was indicated because all the affected farms were served by the same feed factory. A specific PCR-based analysis was developed for positive identification of C. limosum and used to screen archived feed samples from the implicated feed factory. Both C. limosum 16S rRNA genes and C. limosum collagenase genes were identified in both mixed feed and more specifically in raw chicken carcass used as one of the components in the mixed feed, which was therefore identified as the most likely source of contamination. Based on the results of this investigation it is concluded that C. limosum can be associated with abortion and increased mortality in pregnant mink females and it is consequently recommended that raw materials contaminated with C. limosum should be avoided in mink feed, in particular during the whelping season.
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http://dx.doi.org/10.1016/j.vetmic.2017.03.017DOI Listing
May 2017

Effects of Gliadin consumption on the Intestinal Microbiota and Metabolic Homeostasis in Mice Fed a High-fat Diet.

Sci Rep 2017 03 16;7:44613. Epub 2017 Mar 16.

National Food Institute, Technical University of Denmark, 2860 Søborg, Denmark.

Dietary gluten causes severe disorders like celiac disease in gluten-intolerant humans. However, currently understanding of its impact in tolerant individuals is limited. Our objective was to test whether gliadin, one of the detrimental parts of gluten, would impact the metabolic effects of an obesogenic diet. Mice were fed either a defined high-fat diet (HFD) containing 4% gliadin (n = 20), or a gliadin-free, isocaloric HFD (n = 20) for 23 weeks. Combined analysis of several parameters including insulin resistance, histology of liver and adipose tissue, intestinal microbiota in three gut compartments, gut barrier function, gene expression, urinary metabolites and immune profiles in intestinal, lymphoid, liver and adipose tissues was performed. Mice fed the gliadin-containing HFD displayed higher glycated hemoglobin and higher insulin resistance as evaluated by the homeostasis model assessment, more hepatic lipid accumulation and smaller adipocytes than mice fed the gliadin-free HFD. This was accompanied by alterations in the composition and activity of the gut microbiota, gut barrier function, urine metabolome, and immune phenotypes within liver and adipose tissue. Our results reveal that gliadin disturbs the intestinal environment and affects metabolic homeostasis in obese mice, suggesting a detrimental effect of gluten intake in gluten-tolerant subjects consuming a high-fat diet.
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http://dx.doi.org/10.1038/srep44613DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5353615PMC
March 2017

Environmental spread of microbes impacts the development of metabolic phenotypes in mice transplanted with microbial communities from humans.

ISME J 2017 03 18;11(3):676-690. Epub 2016 Nov 18.

National Food Institute, Technical University of Denmark, Søborg, Denmark.

Microbiota transplantation to germ-free animals is a powerful method to study involvement of gut microbes in the aetiology of metabolic syndrome. Owing to large interpersonal variability in gut microbiota, studies with broad coverage of donors are needed to elucidate the establishment of human-derived microbiotas in mice, factors affecting this process and resulting impact on metabolic health. We thus transplanted faecal microbiotas from humans (16 obese and 16 controls) separately into 64 germ-free Swiss Webster mice caged in pairs within four isolators, with two isolators assigned to each phenotype, thereby allowing us to explore the extent of microbial spread between cages in a well-controlled environment. Despite high group-wise similarity between obese and control human microbiotas, transplanted mice in the four isolators developed distinct gut bacterial composition and activity, body mass gain, and insulin resistance. Spread of microbes between cages within isolators interacted with establishment of the transplanted microbiotas in mice, and contributed to the transmission of metabolic phenotypes. Our findings highlight the impact of donor variability and reveal that inter-individual spread of microbes contributes to the development of metabolic traits. This is of major importance for design of animal studies, and indicates that environmental transfer of microbes between individuals may affect host metabolic traits.
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http://dx.doi.org/10.1038/ismej.2016.151DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322303PMC
March 2017

Infant Gut Microbiota Development Is Driven by Transition to Family Foods Independent of Maternal Obesity.

mSphere 2016 Jan-Feb;1(1). Epub 2016 Feb 10.

National Food Institute, Technical University of Denmark, Søborg, Denmark.

The first years of life are paramount in establishing our endogenous gut microbiota, which is strongly affected by diet and has repeatedly been linked with obesity. However, very few studies have addressed the influence of maternal obesity on infant gut microbiota, which may occur either through vertically transmitted microbes or through the dietary habits of the family. Additionally, very little is known about the effect of diet during the complementary feeding period, which is potentially important for gut microbiota development. Here, the gut microbiotas of two different cohorts of infants, born either of a random sample of healthy mothers (n = 114), or of obese mothers (n = 113), were profiled by 16S rRNA amplicon sequencing. Gut microbiota data were compared to breastfeeding patterns and detailed individual dietary recordings to assess effects of the complementary diet. We found that maternal obesity did not influence microbial diversity or specific taxon abundances during the complementary feeding period. Across cohorts, breastfeeding duration and composition of the complementary diet were found to be the major determinants of gut microbiota development. In both cohorts, gut microbial composition and alpha diversity were thus strongly affected by introduction of family foods with high protein and fiber contents. Specifically, intake of meats, cheeses, and Danish rye bread, rich in protein and fiber, were associated with increased alpha diversity. Our results reveal that the transition from early infant feeding to family foods is a major determinant for gut microbiota development. IMPORTANCE The potential influence of maternal obesity on infant gut microbiota may occur either through vertically transmitted microbes or through the dietary habits of the family. Recent studies have suggested that the heritability of obesity may partly be caused by the transmission of "obesogenic" gut microbes. However, the findings presented here suggest that maternal obesity per se does not affect the overall composition of the gut microbiota and its development after introduction of complementary foods. Rather, progression in complementary feeding is found to be the major determinant for gut microbiota establishment. Expanding our understanding of the influence of complementary diet on the development and establishment of the gut microbiota will provide us with the knowledge to tailor a beneficial progression of our intestinal microbial community.
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http://dx.doi.org/10.1128/mSphere.00069-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4863607PMC
June 2016

Antibiotic Treatment Affects Intestinal Permeability and Gut Microbial Composition in Wistar Rats Dependent on Antibiotic Class.

PLoS One 2015 21;10(12):e0144854. Epub 2015 Dec 21.

Division of Diet, Disease prevention and Toxicology, National Food Institute, Technical University of Denmark, Søborg, Denmark.

Antibiotics are frequently administered orally to treat bacterial infections not necessarily related to the gastrointestinal system. This has adverse effects on the commensal gut microbial community, as it disrupts the intricate balance between specific bacterial groups within this ecosystem, potentially leading to dysbiosis. We hypothesized that modulation of community composition and function induced by antibiotics affects intestinal integrity depending on the antibiotic administered. To address this a total of 60 Wistar rats (housed in pairs with 6 cages per group) were dosed by oral gavage with either amoxicillin (AMX), cefotaxime (CTX), vancomycin (VAN), metronidazole (MTZ), or water (CON) daily for 10-11 days. Bacterial composition, alpha diversity and caecum short chain fatty acid levels were significantly affected by AMX, CTX and VAN, and varied among antibiotic treatments. A general decrease in diversity and an increase in the relative abundance of Proteobacteria was observed for all three antibiotics. Additionally, the relative abundance of Bifidobacteriaceae was increased in the CTX group and both Lactobacillaceae and Verrucomicrobiaceae were increased in the VAN group compared to the CON group. No changes in microbiota composition or function were observed following MTZ treatment. Intestinal permeability to 4 kDa FITC-dextran decreased after CTX and VAN treatment and increased following MTZ treatment. Plasma haptoglobin levels were increased by both AMX and CTX but no changes in expression of host tight junction genes were found in any treatment group. A strong correlation between the level of caecal succinate, the relative abundance of Clostridiaceae 1 family in the caecum, and the level of acute phase protein haptoglobin in blood plasma was observed. In conclusion, antibiotic-induced changes in microbiota may be linked to alterations in intestinal permeability, although the specific interactions remain to be elucidated as changes in permeability did not always result from major changes in microbiota and vice versa.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144854PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4686753PMC
June 2016

Having older siblings is associated with gut microbiota development during early childhood.

BMC Microbiol 2015 Aug 1;15:154. Epub 2015 Aug 1.

Division of Diet, Disease Prevention and Toxicology, National Food Institute, Technical University of Denmark, Mørkhøj Bygade 19, DK-2860, Søborg, Denmark.

Background: Evidence suggests that early life infections, presence of older siblings and furred pets in the household affect the risk of developing allergic diseases through altered microbial exposure. Recently, low gut microbial diversity during infancy has also been linked with later development of allergies. We investigated whether presence of older siblings, furred pets and early life infections affected gut microbial communities at 9 and 18 months of age and whether these differences were associated with the cumulative prevalence of atopic symptoms of eczema and asthmatic bronchitis at 3 years of age. Bacterial compositions and diversity indices were determined in fecal samples collected from 114 infants in the SKOT I cohort at age 9 and 18 months by 16S rRNA gene sequencing. These were compared to the presence of older siblings, furred pets and early life infections and the cumulative prevalence of diagnosed asthmatic bronchitis and self-reported eczema at 3 years of age.

Results: The number of older siblings correlated positively with bacterial diversity (p = 0.030), diversity of the phyla Firmicutes (p = 0.013) and Bacteroidetes (p = 0.004) and bacterial richness (p = 0.006) at 18 months. Further, having older siblings was associated with increased relative abundance of several bacterial taxa at both 9 and 18 months of age. Compared to the effect of having siblings, presence of household furred pets and early life infections had less pronounced effects on the gut microbiota. Gut microbiota characteristics were not significantly associated with cumulative occurrence of eczema and asthmatic bronchitis during the first 3 years of life.

Conclusions: Presence of older siblings is associated with increased gut microbial diversity and richness during early childhood, which could contribute to the substantiation of the hygiene hypothesis. However, no associations were found between gut microbiota and atopic symptoms of eczema and asthmatic bronchitis during early childhood and thus further studies are required to elucidate whether sibling-associated gut microbial changes influence development of allergies later in childhood.
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http://dx.doi.org/10.1186/s12866-015-0477-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4522135PMC
August 2015

Dietary xylo-oligosaccharide stimulates intestinal bifidobacteria and lactobacilli but has limited effect on intestinal integrity in rats.

BMC Res Notes 2014 Sep 19;7:660. Epub 2014 Sep 19.

Division of Food Microbiology, National Food Institute, Technical University of Denmark, Mørkhøj Bygade 19, Søborg DK-2860, Denmark.

Background: Consumption of prebiotics may modulate gut microbiota, subsequently affecting the bacterial composition, metabolite profile, and human health. Previous studies indicate that also changes in intestinal integrity may occur. In order to explore this further we have investigated the effect of the putative prebiotic xylo-oligosaccharides (XOS) on the gut microbiota and intestinal integrity in male Wistar rats. As changes in intestinal integrity may be related to the expected bifidogenic effect of XOS, we additionally addressed effects of supplementation with a commensal Bifidobacterium pseudolongum (BIF) isolated from the same breed of laboratory rats.

Results: Changes in faecal and caecal bacterial composition determined by 16S rRNA gene sequencing and quantitative PCR for selected bacterial groups revealed that the overall bacterial composition did not differ markedly between the control (CON), XOS, and BIF groups, when correcting for multiple comparisons. However as hypothesised, the relative abundance of Bifidobacterium spp. was increased in XOS-fed rats as compared to CON in faecal samples after the intervention. Also Lactobacillus spp. was increased in both the XOS and BIF groups in caecum content compared to CON. Intestinal permeability determined in vivo by FITC-dextran permeability and in vitro using extracted caecum water in trans-epithelial resistance (TER) assay showed no effect on intestinal integrity in either the XOS or the BIF groups. However, the expression of occludin, which is part of the tight junction complex, was increased in the XOS group compared to the CON group.

Conclusions: Supplementation with XOS or a commensal Bifidobacterium pseudolongum had very limited effects on intestinal integrity in rats as only significant change in expression of a single tight junction protein gene was found for the XOS group.
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http://dx.doi.org/10.1186/1756-0500-7-660DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4179812PMC
September 2014

Choice of bacterial DNA extraction method from fecal material influences community structure as evaluated by metagenomic analysis.

Microbiome 2014 5;2:19. Epub 2014 Jun 5.

National Food Institute, Technical University of Denmark, Søborg DK-2860, Denmark.

Background: In recent years, studies on the human intestinal microbiota have attracted tremendous attention. Application of next generation sequencing for mapping of bacterial phylogeny and function has opened new doors to this field of research. However, little attention has been given to the effects of choice of methodology on the output resulting from such studies.

Results: IN THIS STUDY WE CONDUCTED A SYSTEMATIC COMPARISON OF THE DNA EXTRACTION METHODS USED BY THE TWO MAJOR COLLABORATIVE EFFORTS: The European MetaHIT and the American Human Microbiome Project (HMP). Additionally, effects of homogenizing the samples before extraction were addressed. We observed significant differences in distribution of bacterial taxa depending on the method. While eukaryotic DNA was most efficiently extracted by the MetaHIT protocol, DNA from bacteria within the Bacteroidetes phylum was most efficiently extracted by the HMP protocol.

Conclusions: Whereas it is comforting that the inter-individual variation clearly exceeded the variation resulting from choice of extraction method, our data highlight the challenge of comparing data across studies applying different methodologies.
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http://dx.doi.org/10.1186/2049-2618-2-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4063427PMC
June 2014

Establishment of intestinal microbiota during early life: a longitudinal, explorative study of a large cohort of Danish infants.

Appl Environ Microbiol 2014 May 28;80(9):2889-900. Epub 2014 Feb 28.

Technical University of Denmark, National Food Institute, Søborg, Denmark.

Fecal samples were obtained from a cohort of 330 healthy Danish infants at 9, 18, and 36 months after birth, enabling characterization of interbacterial relationships by use of quantitative PCR targeting 31 selected bacterial 16S rRNA gene targets representing different phylogenetic levels. Nutritional parameters and measures of growth and body composition were determined and investigated in relation to the observed development in microbiota composition. We found that significant changes in the gut microbiota occurred, particularly from age 9 to 18 months, when cessation of breastfeeding and introduction of a complementary feeding induce replacement of a microbiota characterized by lactobacilli, bifidobacteria, and Enterobacteriaceae with a microbiota dominated by Clostridium spp. and Bacteroides spp. Classification of samples by a proxy enterotype based on the relative levels of Bacteroides spp. and Prevotella spp. showed that enterotype establishment occurs between 9 and 36 months. Thirty percent of the individuals shifted enterotype between 18 and 36 months. The composition of the microbiota was most pronouncedly influenced by the time of cessation of breastfeeding. From 9 to 18 months, a positive correlation was observed between the increase in body mass index and the increase of the short-chain-fatty-acid-producing clostridia, the Clostridum leptum group, and Eubacterium hallii. Considering previously established positive associations between rapid infant weight gain, early breastfeeding discontinuation, and later-life obesity, the corresponding microbial findings seen here warrant attention.
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http://dx.doi.org/10.1128/AEM.00342-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3993305PMC
May 2014

Freezing fecal samples prior to DNA extraction affects the Firmicutes to Bacteroidetes ratio determined by downstream quantitative PCR analysis.

FEMS Microbiol Lett 2012 Apr 6;329(2):193-7. Epub 2012 Mar 6.

National Food Institute, Technical University of Denmark, Søborg, Denmark.

Freezing stool samples prior to DNA extraction and downstream analysis is widely used in metagenomic studies of the human microbiota but may affect the inferred community composition. In this study, DNA was extracted either directly or following freeze storage of three homogenized human fecal samples using three different extraction methods. No consistent differences were observed in DNA yields between extractions on fresh and frozen samples; however, differences were observed between extraction methods. Quantitative PCR analysis was subsequently performed on all DNA samples using six different primer pairs targeting 16S rRNA genes of significant bacterial groups, and the community composition was evaluated by comparing specific ratios of the calculated abundances. In seven of nine cases, the Firmicutes to Bacteroidetes 16S rRNA gene ratio was significantly higher in fecal samples that had been frozen compared to identical samples that had not. This effect was further supported by qPCR analysis of bacterial groups within these two phyla. The results demonstrate that storage conditions of fecal samples may adversely affect the determined Firmicutes to Bacteroidetes ratio, which is a frequently used biomarker in gut microbiology.
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http://dx.doi.org/10.1111/j.1574-6968.2012.02523.xDOI Listing
April 2012

High abundance and diversity of Bacillus anthracis plasmid pXO1-like replicons in municipal wastewater.

FEMS Microbiol Ecol 2010 Oct 30;74(1):241-7. Epub 2010 Jun 30.

Centre for Biosecurity and Biopreparedness, Statens Serum Institut, Copenhagen, Denmark.

Water from the influent of a municipal wastewater treatment plant as well as soil samples collected from the shoreline of 10 lakes were screened for the presence of the Bacillus anthracis pXO1-like plasmid replicon repX using a PCR assay. Specific PCR products were retrieved from all samples, indicating a widespread presence of pXO1-like plasmid replicons in various environmental settings. Initial screening by restriction enzyme analysis revealed at least two forms of the repX gene in the wastewater sample, which was consequently subjected to further investigation. Nine of 51 Bacillus cereus group strains isolated from the wastewater sample were shown to contain a repX-specific gene sequence. Two of these strains were shown to have repX gene sequences with very high homology to the repX gene of plasmid pXO1. The same two strains also contained replicon-specific sequences with high homology to those of pXO2-like plasmids, but did not contain the pXO1-associated cya and lef virulence genes. Collectively, the sequence information from the isolated strains and PCR products obtained using total genomic DNA as a template suggests the existence of three subgroups of pXO1-like plasmid replicons in the wastewater sample.
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http://dx.doi.org/10.1111/j.1574-6941.2010.00922.xDOI Listing
October 2010

All IncP-1 plasmid subgroups, including the novel epsilon subgroup, are prevalent in the influent of a Danish wastewater treatment plant.

Plasmid 2009 Sep 6;62(2):134-9. Epub 2009 Jun 6.

Department of Biology, University of Copenhagen, Denmark.

The presence and diversity of IncP-1 plasmids in the influent of a Danish wastewater treatment plant was studied by PCR amplification of the trfA gene in community DNA followed by sequencing. Three sets of PCR primers were designed to amplify a 281bp fragment of trfA from all currently sequenced IncP-1 plasmids. A neighbor-joining tree, based on a multiple alignment of 72 obtained sequences together with homologous sequences of previously published IncP-1 plasmids, revealed that all established subgroups of IncP-1 plasmids, alpha, beta, gamma and delta, were present in the wastewater treatment plant influent. Also sequences representing the recently described fifth subgroup, the epsilon subgroup, were detected in the wastewater. Thus, these results confirm the presence of at least five phylogenetically distinct subgroups of IncP-1 plasmids and represent the first time that sequences associated with plasmids of all of these five subgroups have been detected in a single setting. Additionally, the results confirm that wastewater constitutes a reservoir for the conjugative IncP-1 plasmids, which often harbor multiple antibiotic resistance genes.
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http://dx.doi.org/10.1016/j.plasmid.2009.05.004DOI Listing
September 2009
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