• Loss of CNFY toxin-induced inflammation drives Yersinia pseudotuberculosis into persistency.

      Heine, Wiebke; Beckstette, Michael; Heroven, Ann Kathrin; Thiemann, Sophie; Heise, Ulrike; Nuss, Aaron Mischa; Pisano, Fabio; Strowig, Till; Dersch, Petra; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-02)
      Gastrointestinal infections caused by enteric yersiniae can become persistent and complicated by relapsing enteritis and severe autoimmune disorders. To establish a persistent infection, the bacteria have to cope with hostile surroundings when they transmigrate through the intestinal epithelium and colonize underlying gut-associated lymphatic tissues. How the bacteria gain a foothold in the face of host immune responses is poorly understood. Here, we show that the CNFY toxin, which enhances translocation of the antiphagocytic Yop effectors, induces inflammatory responses. This results in extensive tissue destruction, alteration of the intestinal microbiota and bacterial clearance. Suppression of CNFY function, however, increases interferon-γ-mediated responses, comprising non-inflammatory antimicrobial activities and tolerogenesis. This process is accompanied by a preterm reprogramming of the pathogen's transcriptional response towards persistence, which gives the bacteria a fitness edge against host responses and facilitates establishment of a commensal-type life style.
    • Microbiota Alters Urinary Bladder Weight and Gene Expression.

      Roje, Blanka; Elek, Anamaria; Palada, Vinko; Bom, Joana; Iljazović, Aida; Šimić, Ana; Sušak, Lana; Vilović, Katarina; Strowig, Till; Vlahoviček, Kristian; et al. (MDPI, 2020-03-17)
      We studied the effect of microbiota on the transcriptome and weight of the urinary bladder by comparing germ-free (GF) and specific pathogen-free (SPF) housed mice. In total, 97 genes were differently expressed (fold change > ±2; false discovery rate (FDR) p-value < 0.01) between the groups, including genes regulating circadian rhythm (Per1, Per2 and Per3), extracellular matrix (Spo1, Spon2), and neuromuscular synaptic transmission (Slc18a3, Slc5a7, Chrnb4, Chrna3, Snap25). The highest increase in expression was observed for immunoglobulin genes (Igkv1-122, Igkv4-68) of unknown function, but surprisingly the absence of microbiota did not change the expression of the genes responsible for recognizing microbes and their products. We found that urinary bladder weight was approximately 25% lighter in GF mice (p = 0.09 for males, p = 0.005 for females) and in mice treated with broad spectrum of antibiotics (p = 0.0002). In conclusion, our data indicate that microbiota is an important determinant of urinary bladder physiology controlling its gene expression and size.
    • Microbiota Normalization Reveals that Canonical Caspase-1 Activation Exacerbates Chemically Induced Intestinal Inflammation.

      Błażejewski, Adrian J; Thiemann, Sophie; Schenk, Alexander; Pils, Marina C; Gálvez, Eric J C; Roy, Urmi; Heise, Ulrike; de Zoete, Marcel R; Flavell, Richard A; Strowig, Till; et al. (2017-06-13)
      Inflammasomes play a central role in regulating intestinal barrier function and immunity during steady state and disease. Because the discoveries of a passenger mutation and a colitogenic microbiota in the widely used caspase-1-deficient mouse strain have cast doubt on previously identified direct functions of caspase-1, we reassessed the role of caspase-1 in the intestine. To this end, we generated Casp1(-/-) and Casp11(-/-) mice and rederived them into an enhanced barrier facility to standardize the microbiota. We found that caspase-11 does not influence caspase-1-dependent processing of IL-18 in homeostasis and during DSS colitis. Deficiency of caspase-1, but not caspase-11, ameliorated the severity of DSS colitis independent of microbiota composition. Ablation of caspase-1 in intestinal epithelial cells was sufficient to protect mice against DSS colitis. Moreover, Casp1(-/-) mice developed fewer inflammation-induced intestinal tumors than control mice. These data show that canonical inflammasome activation controls caspase-1 activity, contributing to exacerbation of chemical-induced colitis.
    • Microbiota-dependent expansion of testicular IL-17-producing Vγ6 γδ T cells upon puberty promotes local tissue immune surveillance.

      Wilharm, Anneke; Brigas, Helena C; Sandrock, Inga; Ribeiro, Miguel; Amado, Tiago; Reinhardt, Annika; Demera, Abdi; Hoenicke, Lisa; Strowig, Till; Carvalho, Tânia; et al. (Springer Nature, 2020-07-30)
      γδT cells represent the majority of lymphocytes in several mucosal tissues where they contribute to tissue homoeostasis, microbial defence and wound repair. Here we characterise a population of interleukin (IL) 17-producing γδ (γδ17) T cells that seed the testis of naive C57BL/6 mice, expand at puberty and persist throughout adulthood. We show that this population is foetal-derived and displays a T-cell receptor (TCR) repertoire highly biased towards Vγ6-containing rearrangements. These γδ17 cells were the major source of IL-17 in the testis, whereas αβ T cells mostly provided interferon (IFN)-γ in situ. Importantly, testicular γδ17 cell homoeostasis was strongly dependent on the microbiota and Toll-like receptor (TLR4)/IL-1α/IL-23 signalling. We further found that γδ17 cells contributed to tissue surveillance in a model of experimental orchitis induced by intra-testicular inoculation of Listeria monocytogenes, as Tcrδ-/- and Il17-/- infected mice displayed higher bacterial loads than wild-type (WT) controls and died 3 days after infection. Altogether, this study identified a previously unappreciated foetal-derived γδ17 cell subset that infiltrates the testis at steady state, expands upon puberty and plays a crucial role in local tissue immune surveillance.
    • Modulation of inflammatory responses by gastrointestinal Prevotella spp. - From associations to functional studies.

      Iljazovic, Aida; Amend, Lena; Galvez, Eric J C; de Oliveira, Romulo; Strowig, Till; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Elsevier, 2021-01-08)
      Numerous studies have associated alterations in the gut microbiota composition with almost every known inflammatory disease. However, proving the biological relevance of distinct microbial signatures and linking specific microorganisms to host phenotypes, remains a considerable challenge. Correspondingly, increased abundance of members of Prevotella genus within microbial communities colonizing distinct mucosal surfaces has been found in individuals diagnosed with rheumatoid arthritis, periodontitis, metabolic disorders, and intestinal and vaginal dysbiosis. Still, the role of Prevotella spp. in the incidence of these diseases continues to be debated. For many years, poor understanding of Prevotella biology could be in large part attributed to the lack of experimental tools. However, in the recent years significant advances have been made towards overcoming these limitations, including increased number of isolates and improved understanding of genetic diversity. Besides discussing the most relevant associations between Prevotella spp. and inflammatory disorders, in the present review we examine the recent efforts to expand the Prevotella experimental "toolbox" and we highlight remaining experimental challenges that should advance future research and our understanding of Prevotella-host interplay.
    • MyD88 signaling in dendritic cells and the intestinal epithelium controls immunity against intestinal infection with C. rodentium.

      Friedrich, Christin; Mamareli, Panagiota; Thiemann, Sophie; Kruse, Friederike; Wang, Zuobai; Holzmann, Bernhard; Strowig, Till; Sparwasser, Tim; Lochner, Matthias; TWINCORE, Zentrum für experimentelle und klinische Infektionsforschung GmbH, Feodor-Lynen Str.7, 30625 Hannover, Germany. (2017-05)
      MyD88-mediated signaling downstream of Toll-like receptors and the IL-1 receptor family is critically involved in the induction of protective host responses upon infections. Although it is known that MyD88-deficient mice are highly susceptible to a wide range of bacterial infections, the cell type-specific contribution of MyD88 in protecting the host against intestinal bacterial infection is only poorly understood. In order to investigate the importance of MyD88 in specific immune and nonimmune cell types during intestinal infection, we employed a novel murine knock-in model for MyD88 that enables the cell type-specific reactivation of functional MyD88 expression in otherwise MyD88-deficient mice. We report here that functional MyD88 signaling in CD11c+ cells was sufficient to activate intestinal dendritic cells (DC) and to induce the early group 3 innate lymphoid cell (ILC3) response as well as the development of colonic Th17/Th1 cells in response to infection with the intestinal pathogen C. rodentium. In contrast, restricting MyD88 signaling to several other cell types, including macrophages (MO), T cells or ILC3 did not induce efficient intestinal immune responses upon infection. However, we observed that the functional expression of MyD88 in intestinal epithelial cells (IEC) also partially protected the mice during intestinal infection, which was associated with enhanced epithelial barrier integrity and increased expression of the antimicrobial peptide RegIIIγ and the acute phase protein SAA1 by epithelial cells. Together, our data suggest that MyD88 signaling in DC and IEC is both essential and sufficient to induce a full spectrum of host responses upon intestinal infection with C. rodentium.
    • Performance, Fermentation Characteristics and Composition of the Microbiome in the Digest of Piglets Kept on a Feed With Humic Acid-Rich Peat.

      Visscher, Christian; Hankel, Julia; Nies, Andrea; Keller, Birgit; Galvez, Eric; Strowig, Till; Keller, Christoph; Breves, Gerhard; HZI, Helmholtz Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig Germany. (Frontiers, 2019-01-01)
      The transition from breast milk to solid feed is a dramatic change in the nutrition of piglets, frequently necessitating antibiotic treatment. In efforts to reduce the use of antibiotics, dietetic concepts based on natural feed additives are becoming more and more important. In the present study, experiments were carried out with 15 rearing piglets (days 28–56) divided into three groups that were offered different diets (Ctr [0% peat]; H1.5 [1.5% peat]; and H3.0 [3.0% peat] based on a commercial weaner recipe; all ~178 g CP, 13.7 MJ ME, 13.3 g Lys, as-fed). The contents of cecal and colon digesta were removed at necropsy. The gas formation (4 h) in colon digesta was measured using in vitro batch fermenters. For microbiome studies, 16S rRNA amplification was performed within the hypervariable region V 4 and sequenced with Illumina MiSeq platform. DNA read mapping and statistical analysis were performed using QIIME (version 1.8.0), MicrobiomeAnalyst, RStudio, and SAS Enterprise Guide. The mean body weight of the animals at the end of the trial did not show statistical differences (in kg: Ctr: 26.1 ± 4.85, H1.5: 28.5 ± 3.41, H3.0: 26.2 ± 4.92). The daily weight gains were high for this age (in g/day; Ctr: 607 ± 157; H1.5: 692 ± 101; H3.0: 615 ± 113) and the feed to gain ratio low (in kg/kg; Ctr: 1.538; H1.5: 1.462; H3.0: 1.462). Concentrations of short-chain fatty acids in the cecal content were significantly lower when peat was used (mmol/kg wet weight; Ctr: 173 ± 30.0; H1.5:134 ± 15.0; H3.0:133 ± 17.3). Numerical differences were found in the gas formation (in mL gas per 10 mL batch in 4 h; Ctr: 7.9 ± 2.2; H1.5: 7.4 ± 2.4; H3.0: 6.6 ± 1.1). The microbiome analyses in the cecal content showed significantly higher values for alpha diversity Chao 1 index for samples from the control group. Significant differences were found for bacterial relative abundance for Tenericutes at phylum level and Mollicutes at class level (p < 0.05) in cecal microbiota. Therefore, there was initial evidence that peat influences intestinal microflora causing a shift in the overall concentration of fermentation products in both, the cecal and the colon content.
    • Perturbation of the gut microbiome by Prevotella spp. enhances host susceptibility to mucosal inflammation.

      Iljazovic, Aida; Roy, Urmi; Gálvez, Eric J C; Lesker, Till R; Zhao, Bei; Gronow, Achim; Amend, Lena; Will, Sabine E; Hofmann, Julia D; Pils, Marina C; et al. (Springer Nature, 2020-05-20)
      Diverse microbial signatures within the intestinal microbiota have been associated with intestinal and systemic inflammatory diseases, but whether these candidate microbes actively modulate host phenotypes or passively expand within the altered microbial ecosystem is frequently not known. Here we demonstrate that colonization of mice with a member of the genus Prevotella, which has been previously associated to colitis in mice, exacerbates intestinal inflammation. Our analysis revealed that Prevotella intestinalis alters composition and function of the ecosystem resulting in a reduction of short-chain fatty acids, specifically acetate, and consequently a decrease in intestinal IL-18 levels during steady state. Supplementation of IL-18 to Prevotella-colonized mice was sufficient to reduce intestinal inflammation. Hence, we conclude that intestinal Prevotella colonization results in metabolic changes in the microbiota, which reduce IL-18 production and consequently exacerbate intestinal inflammation, and potential systemic autoimmunity.
    • Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles.

      Lipinski, Simone; Pfeuffer, Steffen; Arnold, Philipp; Treitz, Christian; Aden, Konrad; Ebsen, Henriette; Falk-Paulsen, Maren; Gisch, Nicolas; Fazio, Antonella; Kuiper, Jan; et al. (2019-09-23)
    • Prdx4 limits caspase‐1 activation and restricts inflammasome‐mediated signaling by extracellular vesicles

      Lipinski, Simone; Pfeuffer, Steffen; Arnold, Philipp; Treitz, Christian; Aden, Konrad; Ebsen, Henriette; Falk‐Paulsen, Maren; Gisch, Nicolas; Fazio, Antonella; Kuiper, Jan; et al. (EMBO Press, 2019-09-23)
      Inflammasomes are cytosolic protein complexes, which orchestrate the maturation of active IL-1β by proteolytic cleavage via caspase-1. Although many principles of inflammasome activation have been described, mechanisms that limit inflammasome-dependent immune responses remain poorly defined. Here, we show that the thiol-specific peroxidase peroxiredoxin-4 (Prdx4) directly regulates IL-1β generation by interfering with caspase-1 activity. We demonstrate that caspase-1 and Prdx4 form a redox-sensitive regulatory complex via caspase-1 cysteine 397 that leads to caspase-1 sequestration and inactivation. Mice lacking Prdx4 show an increased susceptibility to LPS-induced septic shock. This effect was phenocopied in mice carrying a conditional deletion of Prdx4 in the myeloid lineage (Prdx4-ΔLysMCre). Strikingly, we demonstrate that Prdx4 co-localizes with inflammasome components in extracellular vesicles (EVs) from inflammasome-activated macrophages. Purified EVs are able to transmit a robust IL-1β-dependent inflammatory response in vitro and also in recipient mice in vivo. Loss of Prdx4 boosts the pro-inflammatory potential of EVs. These findings identify Prdx4 as a critical regulator of inflammasome activity and provide new insights into remote cell-to-cell communication function of inflammasomes via macrophage-derived EVs
    • Prevotella copri in individuals at risk for rheumatoid arthritis.

      Alpizar-Rodriguez, Deshire; Lesker, Till Robin; Gronow, Achim; Gilbert, Benoît; Raemy, Elena; Lamacchia, Celine; Gabay, Cem; Finckh, Axel; Strowig, Till; HZI, Helmholtz Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig Germany. (BMJ-Journals, 2019-02-13)
      Rheumatoid arthritis (RA) has been associated with a relative expansion of faecal Prevotellaceae. To determine the microbiome composition and prevalence of In an ongoing cohort study of first-degree relatives (FDRs) of patients with RA, we identified 'FDR controls', asymptomatic and without autoantibodies, and individuals in pre-clinical RA stages, who had either developed anticitrullinated peptide antibodies or rheumatoid factor positivity and/or symptoms and signs associated with possible RA. Stool sampling and culture-independent microbiota analyses were performed followed by descriptive statistics and statistical analyses of community structures. A total of 133 participants were included, of which 50 were categorised as 'FDR controls' and 83 in 'pre-clinical RA stages'. The microbiota of individuals in 'pre-clinical RA stages' was significantly altered compared with FDR controls. We found a significant enrichment of the bacterial family Prevotellaceae, particularly spp. enrichment in individuals in pre-clinical stages of RA, before the onset of RA, suggests a role of intestinal dysbiosis in the development of RA.
    • The role of Ames dwarfism and calorie restriction on gut microbiota.

      Wiesenborn, Denise S; Gálvez, Eric J C; Spinel, Lina; Victoria, Berta; Allen, Brittany; Schneider, Augusto; Gesing, Adam; Al-Regaiey, Khalid A; Strowig, Till; Schäfer, Karl-Herbert; et al. (Oxford Academic, 2019-10-30)
      The gut microbiome (GM) represents a large and very complex ecosystem of different microorganisms. There is an extensive interest in the potential role of the GM in different diseases including cancer, diabetes, cardiovascular diseases, and aging. The GM changes over the lifespan and is strongly associated with various age-related diseases. Ames dwarf (df/df) mice are characterized by an extended life- and healthspan, and although these mice are protected from many age-related diseases, their microbiome has not been studied. To determine the role of microbiota on longevity animal models, we investigated the changes in the GM of df/df and Normal control (N) mice, by comparing parents before mating and littermate mice at three distinct time points during early life. Furthermore, we studied the effects of a 6-month calorie restriction (CR), the most powerful intervention extending the lifespan. Our data revealed significant changes of the GM composition during early life development, and we detected differences in the abundance of some bacteria between df/df and N mice, already in early life. Overall, the variability of the microbiota by genotype, time-point and breeding pair showed significant differences. In addition, CR caused significant changes in microbiome according to gastrointestinal (GI) location (distal colon, ileum and cecum), genotype and diet. However, the overall impact of the genotype was more prominent than that of the CR. In conclusion, our findings suggest that the gut microbiota plays an important role during post-natal development in long-living df/df mice and CR dietary regimen can significantly modulate the GM.
    • Sequence and cultivation study of Muribaculaceae reveals novel species, host preference, and functional potential of this yet undescribed family.

      Lagkouvardos, Ilias; Lesker, Till R; Hitch, Thomas C A; Gálvez, Eric J C; Smit, Nathiana; Neuhaus, Klaus; Wang, Jun; Baines, John F; Abt, Birte; Stecher, Bärbel; et al. (BioMedCentral, 2019-02-19)
      Bacteria within family S24-7 (phylum Bacteroidetes) are dominant in the mouse gut microbiota and detected in the intestine of other animals. Because they had not been cultured until recently and the family classification is still ambiguous, interaction with their host was difficult to study and confusion still exists regarding sequence data annotation. We investigated family S24-7 by combining data from large-scale 16S rRNA gene analysis and from functional and taxonomic studies of metagenomic and cultured species. A total of 685 species was inferred by full-length 16S rRNA gene sequence clustering. While many species could not be assigned ecological habitats (93,045 samples analyzed), the mouse was the most commonly identified host (average of 20% relative abundance and nine co-occurring species). Shotgun metagenomics allowed reconstruction of 59 molecular species, of which 34 were representative of the 16S rRNA gene-derived species clusters. In addition, cultivation efforts allowed isolating five strains representing three species, including two novel taxa. Genome analysis revealed that S24-7 spp. are functionally distinct from neighboring families and versatile with respect to complex carbohydrate degradation. We provide novel data on the diversity, ecology, and description of bacterial family S24-7, for which the name Muribaculaceae is proposed.
    • Shaping of Intestinal Microbiota in Nlrp6- and Rag2-Deficient Mice Depends on Community Structure.

      Gálvez, Eric J C; Iljazovic, Aida; Gronow, Achim; Flavell, Richard; Strowig, Till; Helmholtz Zentrum für Infektionsforschung GmbH, Inhoffenstr.7, 38124 Braunschweig, Germany. (2017-12-26)
      Contradicting observations have been made regarding the relative contributions of immune sensors to shaping the microbiome, yet the reasons for these discrepancies are not fully understood. Here, we investigated the contribution of environmental factors in shaping the microbiome in mice deficient in adaptive immunity (Rag2-/-) and Nlrp6, an immune sensor proposed to be involved in regulation of microbiota composition. In conventionally housed Nlrp6-/- mice, familial transmission has a significant effect on microbiota composition, complicating the analysis of genotype-dependent effects. Notably, after rederivation into standardized specific pathogen-free (SPF) conditions devoid of pathobionts, microbiota composition was indistinguishable between WT, Rag2-/-, and Nlrp6-/- mice. However, upon reintroduction of a pathobiont-containing community host, genotype-dependent differences reappear, specifically affecting the relative abundance of pathobionts such as Helicobacter spp. Our results show that the impact of Nlrp6 and also of adaptive immunity on microbiota composition depends on community structure and primarily influences pathobionts but not commensals.
    • Short-chain fatty acids regulate systemic bone mass and protect from pathological bone loss.

      Lucas, Sébastien; Omata, Yasunori; Hofmann, Jörg; Böttcher, Martin; Iljazovic, Aida; Sarter, Kerstin; Albrecht, Olivia; Schulz, Oscar; Krishnacoumar, Brenda; Krönke, Gerhard; et al. (2018)
      Microbial metabolites are known to modulate immune responses of the host. The main metabolites derived from microbial fermentation of dietary fibers in the intestine, short-chain fatty acids (SCFA), affect local and systemic immune functions. Here we show that SCFA are regulators of osteoclast metabolism and bone mass in vivo. Treatment of mice with SCFA as well as feeding with a high-fiber diet significantly increases bone mass and prevents postmenopausal and inflammation-induced bone loss. The protective effects of SCFA on bone mass are associated with inhibition of osteoclast differentiation and bone resorption in vitro and in vivo, while bone formation is not affected. Mechanistically, propionate (C3) and butyrate (C4) induce metabolic reprogramming of osteoclasts resulting in enhanced glycolysis at the expense of oxidative phosphorylation, thereby downregulating essential osteoclast genes such as TRAF6 and NFATc1. In summary, these data identify SCFA as potent regulators of osteoclast metabolism and bone homeostasis.
    • The stem cell-specific long noncoding RNA HOXA10-AS in the pathogenesis of KMT2A-rearranged leukemia.

      Al-Kershi, Sina; Bhayadia, Raj; Ng, Michelle; Verboon, Lonneke; Emmrich, Stephan; Gack, Lucie; Schwarzer, Adrian; Strowig, Till; Heckl, Dirk; Klusmann, Jan-Henning; et al. (American Society of Haematology, 2019-12-23)
      HOX genes are highly conserved, and their precisely controlled expression is crucial for normal hematopoiesis. Accordingly, deregulation of HOX genes can cause leukemia. However, despite of intensive research on the coding HOX genes, the role of the numerous long noncoding RNAs (lncRNAs) within the HOX clusters during hematopoiesis and their contribution to leukemogenesis are incompletely understood. Here, we show that the lncRNA HOXA10-AS, located antisense to HOXA10 and mir-196b in the HOXA cluster, is highly expressed in hematopoietic stem cells (HSCs) as well as in KMT2A-rearranged and NPM1 mutated acute myeloid leukemias (AMLs). Using short hairpin RNA- and locked nucleic acid-conjugated chimeric antisense oligonucleotide (LNA-GapmeR)-mediated HOXA10-AS-knockdown and CRISPR/Cas9-mediated excision in vitro, we demonstrate that HOXA10-AS acts as an oncogene in KMT2A-rearranged AML. Moreover, HOXA10-AS knockdown severely impairs the leukemic growth of KMT2A-rearranged patient-derived xenografts in vivo, while high HOXA10-AS expression can serve as a marker of poor prognosis in AML patients. Lentiviral expression of HOXA10-AS blocks normal monocytic differentiation of human CD34+ hematopoietic stem and progenitor cells. Mechanistically, we show that HOXA10-AS localizes in the cytoplasm and acts in trans to induce NF-κB target genes. In total, our data imply that the normally HSC-specific HOXA10-AS is an oncogenic lncRNA in KMT2A-r AML. Thus, it may also represent a potential therapeutic target in KMT2A-rearranged AML.
    • Successful Fecal Microbiota Transplantation in a Patient with Severe Complicated Clostridium difficile Infection after Liver Transplantation.

      Schneider, Kai Markus; Wirtz, Theresa H; Kroy, Daniela; Albers, Stefanie; Neumann, Ulf Peter; Strowig, Till; Sellge, Gernot; Trautwein, Christian; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-05-18)
      Clostridium difficile infection (CDI) represents one of the most common healthcare-associated infections. Due to increasing numbers of recurrences and therapy failures, CDI has become a major disease burden. Studies have shown that fecal microbiota transplantation (FMT) can both be a safe and highly efficacious therapy for patients with therapy-refractory CDI. However, patients undergoing solid organ transplantation are at high risk for CDI due to long-term immunosuppression, previous antibiotic therapy, and proton pump inhibitor use. Additionally, these patients may be especially prone to adverse events related to FMT. Here, we report a successful FMT in a patient with severe therapy-refractory CDI after liver transplantation.
    • Variations in microbiota composition of laboratory mice influence Citrobacter rodentium infection via variable short-chain fatty acid production.

      Osbelt, Lisa; Thiemann, Sophie; Smit, Nathiana; Lesker, Till Robin; Schröter, Madita; Gálvez, Eric J C; Schmidt-Hohagen, Kerstin; Pils, Marina C; Mühlen, Sabrina; Dersch, Petra; et al. (PLOS, 2020-03-24)
      The composition of the intestinal microbiota influences the outcome of enteric infections in human and mice. However, the role of specific members and their metabolites contributing to disease severity is largely unknown. Using isogenic mouse lines harboring distinct microbiota communities, we observed highly variable disease kinetics of enteric Citrobacter rodentium colonization after infection. Transfer of communities from susceptible and resistant mice into germ-free mice verified that the varying susceptibilities are determined by microbiota composition. The strongest differences in colonization were observed in the cecum and could be maintained in vitro by coculturing cecal bacteria with C. rodentium. Cohousing of animals as well as the transfer of cultivable bacteria from resistant to susceptible mice led to variable outcomes in the recipient mice. Microbiome analysis revealed that a higher abundance of butyrate-producing bacteria was associated with the resistant phenotype. Quantification of short-chain fatty acid (SCFA) levels before and after infection revealed increased concentrations of acetate, butyrate and propionate in mice with delayed colonization. Addition of physiological concentrations of butyrate, but not of acetate and/or propionate strongly impaired growth of C. rodentium in vitro. In vivo supplementation of susceptible, antibiotic-treated and germ-free mice with butyrate led to the same level of protection, notably only when cecal butyrate concentration reached a concentration higher than 50 nmol/mg indicating a critical threshold for protection. In the recent years, commensal-derived primary and secondary bacterial metabolites emerged as potent modulators of hosts susceptibility to infection. Our results provide evidence that variations in SCFA production in mice fed fibre-rich chow-based diets modulate susceptibility to colonization with Enterobacteriaceae not only in antibiotic-disturbed ecosystems but even in undisturbed microbial communities. These findings emphasise the need for microbiota normalization across laboratory mouse lines for infection experiments with the model-pathogen C. rodentium independent of investigations of diet and antibiotic usage.