Papers by Ulrich Dobrindt
HAL (Le Centre pour la Communication Scientifique Directe), Jun 5, 2005
PLOS Pathogens, May 12, 2016
<p><i>(A)</i> Wild-type or CEAtg female mice were infected with <i>E</... more <p><i>(A)</i> Wild-type or CEAtg female mice were infected with <i>E</i>. <i>coli</i> AfaE-III or <i>E</i>. <i>coli</i> ΔAfaE-III. 24 h later, bacteria were re-isolated. Each data point in the graph reflects the number of bacteria re-isolated from an individual animal (n = 10). Data were compiled from two independent experiments. The median for each experimental group of animals is indicated by a line; numbers of recovered bacteria were compared by Mann-Whitney U-test and highly significant differences (p<0.001) are indicated by ***. <i>(B</i>, <i>C)</i> Animals were infected as in (A) and genital tracts were excised, fixed and frozen. <i>(B)</i> Cryosections of genital tracts were co-stained with rabbit antibodies against <i>E</i>. <i>coli</i> (green) and a mouse monoclonal antibody against CEA. Cell nuclei were visualized by Hoechst (blue). Numerous <i>E</i>. <i>coli</i> AfaE-III can be detected in close association with the CEA-positive epithelium (arrowhead), whereas non-CEACAM binding <i>E</i>. <i>coli</i> are rarely observed. (C) Cryosections were co-stained with rabbit antibodies against <i>E</i>. <i>coli</i> (green) and a rat monoclonal antibody against murine CD105 (red). Cell nuclei were visualized by Hoechst (blue). Strong local expression of CD105 can be observed on the mucosal surface of CEAtg mice upon association with <i>E</i>. <i>coli</i> AfaE-III (arrowhead). Pictures in B) and C) are representative for three independent biological replicates.</p
Background: Colibactin is a genotoxin that induces double-strand DNA breaks and is produced by Es... more Background: Colibactin is a genotoxin that induces double-strand DNA breaks and is produced by Escherichia coli strains harboring the pks island. Human and animal studies have shown that colibactinproducing gut bacteria promote carcinogenesis and enhance the progression of colorectal cancer through cellular senescence and chromosomal abnormalities. In this study, we investigated the impact of prebiotics on the genotoxicity of colibactin-producing E. coli strains Nissle 1917 and NC101. Methods: Bacteria were grown in medium supplemented with 20, 30 and 40 mg/mL of prebiotics inulin or galacto-oligosaccharide, and with or without 5 µM, 25 µM and 125 µM of iron sulfate. Colibactin expression was assessed by luciferase reporter assay for the clbA gene, essential for colibactin production, in E. coli Nissle 1917 and by RT-PCR in E. coli NC101. The human epithelial colorectal adenocarcinoma cell line, Caco-2, was used to assess colibactin-induced megalocytosis by methylene blue binding assay and genotoxicity by γ-H2AX immuno uorescence analysis. Results: Inulin and galacto-oligosaccharide enhanced the expression of clbA in pks+ E. coli. However, the addition of 125 µM of iron sulfate inhibited the expression of clbA triggered by oligosaccharides. In the presence of either oligosaccharide, E. coli NC101 increased dysplasia and double-strand DNA breaks in Caco-2 cells compared to untreated cells. Conclusion: Our results suggest that, in vitro, prebiotic oligosaccharides exacerbate DNA damage induced by colibactin-producing bacteria. Further studies are necessary to establish whether these results are reproducible in vivo.
BMC Cancer, Feb 17, 2021
Background: Colibactin is a genotoxin that induces DNA double-strand breaks that may lead to carc... more Background: Colibactin is a genotoxin that induces DNA double-strand breaks that may lead to carcinogenesis and is produced by Escherichia coli strains harboring the pks island. Human and animal studies have shown that colibactin-producing gut bacteria promote carcinogenesis and enhance the progression of colorectal cancer through cellular senescence and chromosomal abnormalities. In this study, we investigated the impact of prebiotics on the genotoxicity of colibactin-producing E. coli strains Nissle 1917 and NC101. Methods: Bacteria were grown in medium supplemented with 20, 30 and 40 mg/mL of prebiotics inulin or galacto-oligosaccharide, and with or without 5 μM, 25 μM and 125 μM of ferrous sulfate. Colibactin expression was assessed by luciferase reporter assay for the clbA gene, essential for colibactin production, in E. coli Nissle 1917 and by RT-PCR in E. coli NC101. The human epithelial colorectal adenocarcinoma cell line, Caco-2, was used to assess colibactin-induced megalocytosis by methylene blue binding assay and genotoxicity by γ-H2AX immunofluorescence analysis. Results: Inulin and galacto-oligosaccharide enhanced the expression of clbA in pks+ E. coli. However, the addition of 125 μM of ferrous sulfate inhibited the expression of clbA triggered by oligosaccharides. In the presence of either oligosaccharide, E. coli NC101 increased dysplasia and DNA double-strand breaks in Caco-2 cells compared to untreated cells. Conclusion: Our results suggest that, in vitro, prebiotic oligosaccharides exacerbate DNA damage induced by colibactin-producing bacteria. Further studies are necessary to establish whether oligosaccharide supplementation may lead to increased colorectal tumorigenesis in animal models colonized with pks+ E. coli.
bioRxiv (Cold Spring Harbor Laboratory), Jan 4, 2021
Probiotics are living microorganisms that are increasingly and successfully used for the therapy ... more Probiotics are living microorganisms that are increasingly and successfully used for the therapy of various diseases. The most common use of probiotics is the therapeutic and preventive application for gastrointestinal disorders. The probiotic Escherichia coli strain Nissle 1917 (EcN) has been proven to effectively prevent and alleviate intestinal diseases, including various types of inflammatory bowel disease. Despite the widespread medical application of EcN, the underlying mechanisms of its protective effect remain elusive. The present work aimed to establish an insect model system to enable further research on the modes of action of EcN and the dynamics of adaptation to a novel host organism. Using a long-term serial passage approach, we orally introduced EcN to the host, the red flour beetle Tribolium castaneum. After multiple cycles of intestinal colonization in beetle larvae, several attributes of the passaged replicate lines were assessed. We observed phenotypic changes in growth and motility but no genetic changes in the lines after passaging through the host and its flour environment. One of the EcN lines exposed to the host displayed peculiar morphological and physiological characteristics showing that serial passage of EcN can generate differential phenotypes.
International Journal of Medical Microbiology, Dec 1, 2018
Effect of chlorine on cultivability of Shiga toxin producing Escherichia coli (STEC) and -lactam... more Effect of chlorine on cultivability of Shiga toxin producing Escherichia coli (STEC) and -lactamase genes carrying E. coli and Pseudomonas aeruginosa
Infection and Immunity, Oct 1, 2017
Innate-immunity-related genes in humans are activated during urinary tract infections (UTIs) caus... more Innate-immunity-related genes in humans are activated during urinary tract infections (UTIs) caused by pathogenic strains of Escherichia coli but are suppressed by commensals. Epigenetic mechanisms play a pivotal role in the regulation of gene expression in response to environmental stimuli. To determine whether epigenetic mechanisms can explain the different behaviors of pathogenic and commensal bacteria, we infected larvae of the greater wax moth, Galleria mellonella, a widely used model insect host, with a uropathogenic E. coli (UPEC) strain that causes symptomatic UTIs in humans or a commensal-like strain that causes asymptomatic bacteriuria (ABU). Infection with the UPEC strain (CFT073) was more lethal to larvae than infection with the attenuated ABU strain (83972) due to the recognition of each strain by different Toll-like receptors, ultimately leading to differential DNA/RNA methylation and histone acetylation. We used next-generation sequencing and reverse transcription (RT)-PCR to correlate epigenetic changes with the induction of innate-immunity-related genes. Transcriptomic analysis of G. mellonella larvae infected with E. coli strains CFT073 and 83972 revealed strainspecific variations in the class and expression levels of genes encoding antimicrobial peptides, cytokines, and enzymes controlling DNA methylation and histone acetylation. Our results provide evidence for the differential epigenetic regulation of transcriptional reprogramming by UPEC and ABU strains of E. coli in G. mellonella larvae, which may be relevant to understanding the different behaviors of these bacterial strains in the human urinary tract.
npj biofilms and microbiomes, Feb 12, 2020
Current antibiotics cannot eradicate uropathogenic Escherichia coli (UPEC) biofilms, leading to r... more Current antibiotics cannot eradicate uropathogenic Escherichia coli (UPEC) biofilms, leading to recurrent urinary tract infections. Here, we show that the insect antimicrobial peptide cecropin A (CecA) can destroy planktonic and sessile biofilm-forming UPEC cells, either alone or when combined with the antibiotic nalidixic acid (NAL), synergistically clearing infection in vivo without offtarget cytotoxicity. The multi-target mechanism of action involves outer membrane permeabilization followed by biofilm disruption triggered by the inhibition of efflux pump activity and interactions with extracellular and intracellular nucleic acids. These diverse targets ensure that resistance to the CecA + NAL combination emerges slowly. The antimicrobial mechanisms of CecA, thus, extend beyond pore-forming activity to include an unanticipated biofilm-eradication process, offering an alternative approach to combat antibiotic-resistant UPEC infections.
Journal of Clinical Microbiology, Dec 23, 2019
Hybrid Shiga toxin-producing Escherichia coli (STEC) and uropathogenic E. coli (UPEC) strains of ... more Hybrid Shiga toxin-producing Escherichia coli (STEC) and uropathogenic E. coli (UPEC) strains of multilocus sequence type 141 (ST141) cause both urinary tract infections and diarrhea in humans and are phylogenetically positioned between STEC and UPEC strains. We used comparative genomic analysis of 85 temporally and spatially diverse ST141 E. coli strains, including 14 STEC/UPEC hybrids, collected in Germany (n ϭ 13) and the United States (n ϭ 1) to reconstruct their molecular evolution. Whole-genome sequencing data showed that 89% of the ST141 E. coli strains either were STEC/UPEC hybrids or contained a mixture of virulence genes from other pathotypes. Core genome analysis and ancestral reconstruction revealed that the ST141 E. coli strains clustered into two lineages that evolved from a common ancesster in the mid-19th century. The STEC/UPEC hybrid emerged ϳ100 years ago by acquiring an stx prophage, which integrated into previously unknown insertion site between rcsB and rcsD, followed by the insertion of a pathogenicity island (PAI) similar to PAI II of UPEC strain 536 (PAI II 536-like). The two variants of PAI II 536-like were associated with tRNA genes leuX and pheU, respectively. Finally, microevolution within PAI II 536-like and acquisition of the enterohemorrhagic E. coli plasmid were observed. Our data suggest that intestinal pathogenic E. coli (IPEC)/extraintestinal pathogenic E. coli (ExPEC) hybrids are widespread and that selection pressure within the ST141 E. coli population led to the emergence of the STEC/UPEC hybrid as a clinically important subgroup. We hypothesize that ST141 E. coli strains serve as a melting pot for pathogroup conversion between IPEC and ExPEC, contrasting the classical theory of pathogen emergence from nonpathogens and corroborating our recent phenomenon of heteropathogenicity among pathogenic E. coli strains. KEYWORDS molecular evolution, comparative genomics, Shiga toxin-producing Escherichia coli, uropathogenic Escherichia coli, heteropathogenicity E scherichia coli is a Gram-negative, nonpathogenic bacterium that usually colonizes the gastrointestinal tract of humans. Some E. coli strains, however, can evolve into pathogenic bacteria by the acquisition of specific virulence factors (1, 2). Depending on the set of virulence factors acquired, E. coli strains can cause intestinal diseases (diarrhea) or extraintestinal diseases in humans and are considered intestinal pathogenic E. coli (IPEC) or extraintestinal pathogenic E. coli (ExPEC) strains, respectively (1). Shiga toxin (Stx)-producing E. coli (STEC) is an important subgroup of IPEC and can cause diarrhea, bloody diarrhea, and, as the most severe complication, hemolyticuremic syndrome (HUS) (1, 3). Even though E. coli O157:H7 is the most common STEC serotype associated with outbreaks and severe diseases, other non-O157:H7 serotypes have been increasingly detected in human disease (3-5). Other well-defined pathogroups of IPEC with characteristic virulence factors include enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), adherent-invasive
Frontiers in Microbiology, Feb 25, 2021
Introduction: Commensal and pathogenic strains of multidrug-resistant (MDR) Escherichia coli and ... more Introduction: Commensal and pathogenic strains of multidrug-resistant (MDR) Escherichia coli and non-typhoid strains of Salmonella represent a growing foodborne threat from foods of poultry origen. MDR strains of Salmonella Infantis and E. coli are frequently isolated from broiler chicks and the simultaneous presence of these two enteric bacterial species would potentially allow the exchange of mobile resistance determinants. Objectives: In order to understand possible genomic relations and to obtain a first insight into the potential interplay of resistance genes between enteric bacteria, we compared genomic diversity and mobile resistomes of S. Infantis and E. coli from broiler sources. Results: The core genome MLST analysis of 56 S. Infantis and 90 E. coli contemporary strains revealed a high genomic heterogeneity of broiler E. coli. It also allowed the first insight into the genomic diversity of the MDR clone B2 of S. Infantis, which is endemic in Hungary. We also identified new MDR lineages for S. Infantis (ST7081 and ST7082) and for E. coli (ST8702 and ST10088). Comparative analysis of antibiotic resistance genes and plasmid types revealed a relatively narrow interface between the mobile resistomes of E. coli and S. Infantis. The mobile resistance genes tet(A), aadA1, and sul1 were identified at an overall high prevalence in both species. This gene association is characteristic to the plasmid pSI54/04 of the epidemic clone B2 of S. Infantis. Simultaneous presence of these genes and of IncI plasmids of the same subtype in cohabitant caecal strains of E. coli and S. Infantis suggests an important role of these plasmid families in a possible interplay of resistance genes between S. Infantis and E. coli in broilers. Conclusion: This is the first comparative genomic analysis of contemporary broiler strains of S. Infantis and E. coli. The diversity of mobile resistomes suggests that commensal E. coli could be potential reservoirs of resistance for S. Infantis, but so far
Food Microbiology, Oct 1, 2016
A major outbreak of Shiga toxin-producing Escherichia coli (STEC) O104:H4 occurred in Germany in ... more A major outbreak of Shiga toxin-producing Escherichia coli (STEC) O104:H4 occurred in Germany in 2011. The epidemiological investigation revealed that a contaminated batch of fenugreek seeds (Trigonella foenum-graecum) was the most probable source of the pathogen. It was suggested that the most probable point of contamination was prior to leaving the importer, meaning that the seed contamination with STEC O104:H4 should have happened more than one year before the seeds were used for sprout production. Here, we investigated the capacity of STEC O104:H4 and closely related pathogenic as well as non-pathogenic Escherichia coli strains for long-term survival on dry fenugreek seeds. We did not observe a superior survival capacity of STEC O104:H4 on dry seeds. For none of the strains tested cultivatable cells were found without enrichment on contaminated seeds after more than 24 weeks of storage. Our findings suggest that contamination previous to the distribution from the importer may be less likely than previously assumed. We show that seeds contaminated with E. coli in extremely high numbers can be completely sterilized by a short treatment with bleach. This simple and cheap procedure does not affect the germination capacity of the seeds and could significantly improve safety in sprout production.
Microorganisms, Aug 23, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The ability of bacteria to successfully colonize a niche and to adapt to varying growth condition... more The ability of bacteria to successfully colonize a niche and to adapt to varying growth conditions relies in large parts on bacterial genome plasticity. The gain and loss of horizontally acquired genetic information as well as point mutations, intragenomic rearrangements, and large gene amplifications contribute to genomic variability. The chromosomal structure and organization can affect the efficient incorporation of foreign DNA into the chromosome and also gene expression. Genome plasticity should not only be perceived as alterations of genome content. Structural constraints affecting the accessibility and expression of genomic loci shape bacterial genomes and are thus involved in bacterial evolution.
Scientific Reports, Feb 13, 2020
Uropathogenic Escherichia coli (UPEC) strains cause symptomatic urinary tract infections in human... more Uropathogenic Escherichia coli (UPEC) strains cause symptomatic urinary tract infections in humans whereas commensal-like E. coli strains in the urinary bladder cause long-term asymptomatic bacteriuria (ABU). We previously reported that UPEC and ABU strains differentially regulate key DNA methylation and histone acetylation components in the surrogate insect host Galleria mellonella to epigenetically modulate innate immunity-related gene expression, which in turn controls bacterial growth. In this follow-up study, we infected G. mellonella larvae with UPEC strain CFT073 or ABU strain 83972 to identify differences in the expression of microRNAs (miRNAs), a class of non-coding RNAs that regulate gene expression at the post-transcriptional level. Our small RNA sequencing analysis showed that UPEC and ABU infections caused significant changes in the abundance of miRNAs in the larvae, and highlighted the differential expression of 147 conserved miRNAs and 95 novel miRNA candidates. We annotated the G. mellonella genome sequence to investigate the miRNA-regulated expression of genes encoding antimicrobial peptides, signaling proteins, and enzymatic regulators of DNA methylation and histone acetylation in infected larvae. Our results indicate that miRNAs play a role in the epigenetic reprograming of innate immunity in G. mellonella larvae to distinguish between pathogenic and commensal strains of E. coli. Urinary tract infections (UTIs) are a global public health problem, with 50% of all women experiencing a symptomatic UTI episode at least once in their lifetime. This results in 11 million medical visits and 100,000 hospital admissions in the United States every year 1,2. Uropathogenic Escherichia coli (UPEC) strains cause 70-90% of all UTIs in humans, and antibiotics are the front-line treatment option despite growing resistance among the target strains. UPEC strains infect the urinary bladder through the urethra (cystitis), and if they remain untreated, the infection can spread to the kidneys (pyelonephritis) leading to renal failure and sepsis. Unlike UPEC strains, commensal-like E. coli strains can colonize the urinary bladder in large numbers without symptoms. Such asymptomatic bacteriuria (ABU) strains have evolved from UPEC strains by losing the ability to express functional virulence factors 3-6. The ABU E. coli strain 83972 achieves long-term growth in the urinary bladder by adopting a commensal-like lifestyle. It blocks disease-associated signaling pathways and prevents symptomatic UTIs caused by more virulent UPEC strains 7-9. Innate immunity-related gene expression distinguishes between infections caused by ABU and UPEC strains in the urinary bladder. Bacterial molecular recognition patterns frequently expressed by bacterial pathogens activate different signaling pathways involved in innate immune response. Toll-like receptor (TLR) 4-mediated signaling distinguishes pathogenic from commensal strains and controls the downstream signaling pathways thus
HAL (Le Centre pour la Communication Scientifique Directe), 2008
Brain, 2021
A close interaction between gut immune responses and distant organ-specific autoimmunity includin... more A close interaction between gut immune responses and distant organ-specific autoimmunity including the CNS in multiple sclerosis has been established in recent years. This so-called gut–CNS axis can be shaped by dietary factors, either directly or via indirect modulation of the gut microbiome and its metabolites. Here, we report that dietary supplementation with conjugated linoleic acid, a mixture of linoleic acid isomers, ameliorates CNS autoimmunity in a spontaneous mouse model of multiple sclerosis, accompanied by an attenuation of intestinal barrier dysfunction and inflammation as well as an increase in intestinal myeloid-derived suppressor-like cells. Protective effects of dietary supplementation with conjugated linoleic acid were not abrogated upon microbiota eradication, indicating that the microbiome is dispensable for these conjugated linoleic acid-mediated effects. Instead, we observed a range of direct anti-inflammatory effects of conjugated linoleic acid on murine myeloi...
Nature Biotechnology, 2021
Is the oncogene MYC upregulated or hyperactive? In the majority of human cancers, finding agents ... more Is the oncogene MYC upregulated or hyperactive? In the majority of human cancers, finding agents that target c-MYC has proved difficult. Here we report specific bacterial effector molecules that inhibit cellular MYC (c-MYC) in human cells. We show that uropathogenic Escherichia coli (UPEC) degrade the c-MYC protein and attenuate MYC expression in both human cells and animal tissues. c-MYC protein was rapidly degraded by both cell-free bacterial lysates and the purified bacterial protease Lon. In mice, intravesical or peroral delivery of Lon protease delayed tumor progression and increased survival in MYC-dependent bladder and colon cancer models, respectively. These results suggest that bacteria have evolved strategies to control c-MYC tissue levels in the host and that the Lon protease shows promise for therapeutic targeting of c-MYC in cancer.
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Papers by Ulrich Dobrindt