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The environmental bacterium Klebsiella oxytoca displays an alarming increase of antibiotic-resistant strains that frequently cause outbreaks in intensive care units. Due to its prevalence in the environment and opportunistic presence in humans, molecular surveillance (including resistance marker screening) and high-resolution cluster analysis are of high relevance. Furthermore, K. oxytoca previously described in studies is rather a species complex (KoSC) than a single species comprising at least six closely related species that are not easily differentiated by standard typing methods. To reach a discriminatory power high enough to identify and resolve clusters within these species, whole genome sequencing is necessary. The resolution is achievable with core genome multilocus sequence typing (cgMLST) extending typing of a few housekeeping genes to thousands of core genome genes. CgMLST is highly standardized and provides a nomenclature enabling cross laboratory reproducibility and data exchange for routine diagnostics. Here, we established a cgMLST scheme not only capable of resolving the KoSC species but also producing reliable and consistent results for published outbreaks. Our cgMLST scheme consists of 2,536 core genome and 2,693 accessory genome targets, with a percentage of good cgMLST targets of 98.31% in 880 KoSC genomes downloaded from the National Center for Biotechnology Information (NCBI). We also validated resistance markers against known resistance gene patterns and successfully linked genetic results to phenotypically confirmed toxic strains carrying the til gene cluster. In conclusion, our novel cgMLST enables highly reproducible typing of four different clinically relevant species of the KoSC and thus facilitates molecular surveillance and cluster investigations.
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Genoma Bacteriano , Klebsiella oxytoca , Tipificación de Secuencias Multilocus , Tipificación de Secuencias Multilocus/métodos , Klebsiella oxytoca/genética , Klebsiella oxytoca/clasificación , Klebsiella oxytoca/aislamiento & purificación , Humanos , Genoma Bacteriano/genética , Filogenia , Infecciones por Klebsiella/microbiología , Secuenciación Completa del Genoma , Técnicas de Tipificación Bacteriana/métodos , Genes Esenciales/genética , Reproducibilidad de los ResultadosRESUMEN
OBJECTIVES: Klebsiella oxytoca is a gastrointestinal pathobiont with the potential to produce the toxins tilivalline and tilimycin, which cause antibiotic-associated hemorrhagic colitis. Overgrowth of toxigenic K oxytoca has recently been implicated in necrotizing enterocolitis. K oxytoca colonizes 2-9% of healthy adults, however, there is no systematic data on colonization in healthy children. We investigated K oxytoca colonization and its toxigenic properties in healthy infants. METHODS: We sampled stool of healthy infants and determined K oxytoca colonization using stool culture and PCR (pehX). Toxin in stool was measured with HPLC/high-resolution mass spectrometry. K oxytoca isolates were typed using multi-locus sequence typing (MLST) and K oxytoca toxin PCR (npsA/B). Cytotoxin production of isolates was analyzed by MTT assay. RESULTS: K oxytoca was detected in 30 of 61 infants (49%) using stool culture and in 45 of 61 (73%) using PCR (pehX). Toxin marker PCR (npsA/B) was positive in 66% of stool samples positive for K oxytoca PCR. Stool toxin levels were too low for quantitation but traces of tilivalline were detected. Contrarily, 49% of K oxytoca isolates demonstrated toxicity in the MTT assay. MLST revealed 36 distinct sequence types affiliated with all known K oxytoca sequence type clusters (A, B1 and B2). CONCLUSIONS: More than 70% of healthy infants were colonized with K oxytoca. Toxin quantities in stool of colonized healthy infants were below detection level, yet half of the isolates produced toxin in vitro demonstrating their pathobiont potential. The high occurrence of toxigenic K oxytoca in healthy infants has to be considered for future disease association studies.
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Enterocolitis Seudomembranosa , Infecciones por Klebsiella , Adulto , Niño , Heces , Humanos , Lactante , Recién Nacido , Infecciones por Klebsiella/complicaciones , Infecciones por Klebsiella/diagnóstico , Klebsiella oxytoca/genética , Tipificación de Secuencias MultilocusRESUMEN
Establishing causal links between bacterial metabolites and human intestinal disease is a significant challenge. This study reveals the molecular basis of antibiotic-associated hemorrhagic colitis (AAHC) caused by intestinal resident Klebsiella oxytoca Colitogenic strains produce the nonribosomal peptides tilivalline and tilimycin. Here, we verify that these enterotoxins are present in the human intestine during active colitis and determine their concentrations in a murine disease model. Although both toxins share a pyrrolobenzodiazepine structure, they have distinct molecular targets. Tilimycin acts as a genotoxin. Its interaction with DNA activates damage repair mechanisms in cultured cells and causes DNA strand breakage and an increased lesion burden in cecal enterocytes of colonized mice. In contrast, tilivalline binds tubulin and stabilizes microtubules leading to mitotic arrest. To our knowledge, this activity is unique for microbiota-derived metabolites of the human intestine. The capacity of both toxins to induce apoptosis in intestinal epithelial cells-a hallmark feature of AAHC-by independent modes of action, strengthens our proposal that these metabolites act collectively in the pathogenicity of colitis.
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Enterocolitis Seudomembranosa/genética , Enterotoxinas/metabolismo , Interacciones Microbiota-Huesped/genética , Klebsiella oxytoca/genética , Animales , Benzodiazepinonas/metabolismo , Benzodiazepinonas/toxicidad , Daño del ADN/efectos de los fármacos , Enterocolitis Seudomembranosa/microbiología , Enterocolitis Seudomembranosa/patología , Enterotoxinas/biosíntesis , Células Epiteliales/microbiología , Células Epiteliales/patología , Humanos , Intestinos/microbiología , Intestinos/patología , Infecciones por Klebsiella/genética , Infecciones por Klebsiella/microbiología , Klebsiella oxytoca/metabolismo , Klebsiella oxytoca/patogenicidad , Ratones , Microtúbulos/efectos de los fármacos , Oxiquinolina/análogos & derivados , Oxiquinolina/metabolismo , Oxiquinolina/toxicidad , Péptidos/metabolismo , Péptidos/toxicidadRESUMEN
BACKGROUND: Various observational studies have examined a potential relationship between Helicobacter pylori colonization and inflammatory bowel diseases (IBDs); however, results are inconclusive. This systematic review evaluates articles reporting an association between human H. pylori colonization and IBD. METHODS: A systematic search of studies was conducted to evaluate a possible relationship between H. pylori colonization and IBD. Seven databases and different types of gray literature were searched. After screening for relevant articles, selection and data extraction were done. After that, the data were analyzed, and pooled odds ratios (ORs) were calculated, using meta-analysis. Heterogeneity, sensitivity, and subgroups analyses were conducted. Funnel plots followed by Begg and Egger tests were done to assess the publication bias. RESULTS: Among 58 studies, including 13,549 patients with IBD and 506,554 controls, the prevalence of H. pylori colonization was 22.74% and 36.30%, respectively. A significant negative association was observed between H. pylori colonization and IBD (pooled OR: 0.45, 95% confidence interval 0.39-0.53, P≤0.001). The random-effect model showed significant statistical heterogeneity in the included studies (I2=79%). No publication bias was observed. Among subgroups, ORs were notably different when the data were stratified by the age difference between patient and control group, and by study regions and/or continent. Finally, the meta-regression analysis showed significant results, in terms of the age difference and region variables. CONCLUSIONS: In this meta-analysis, all statistical data support the theory that H. pylori has a protective role in IBD. However, more primary studies using proper methodology are needed to confirm this association.
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Colitis , Infecciones por Helicobacter , Helicobacter pylori , Enfermedades Inflamatorias del Intestino , Infecciones por Helicobacter/epidemiología , Humanos , Enfermedades Inflamatorias del Intestino/epidemiología , Oportunidad RelativaRESUMEN
Leupeptin is a bacterial small molecule that is used worldwide as a protease inhibitor. However, its biosynthesis and genetic distribution remain unknown. We identified a family of leupeptins in gammaproteobacterial pathogens, including Photorhabdus, Xenorhabdus, and Klebsiella species, amongst others. Through genetic, metabolomic, and heterologous expression analyses, we established their construction by discretely expressed ligases and accessory enzymes. In Photorhabdus species, a hypothetical protein required for colonizing nematode hosts was established as a new class of proteases. This enzyme cleaved the tripeptide aldehyde protease inhibitors, leading to the formation of "pro-pyrazinones" featuring a hetero-tricyclic architecture. In Klebsiella oxytoca, the pathway was enriched in clinical isolates associated with respiratory tract infections. Thus, the bacterial production and proteolytic degradation of leupeptins can be associated with animal colonization phenotypes.
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Gammaproteobacteria/metabolismo , Leupeptinas/farmacología , Inhibidores de Proteasas/farmacología , Animales , Gammaproteobacteria/patogenicidad , Leupeptinas/metabolismo , Inhibidores de Proteasas/metabolismoRESUMEN
Corpus-dominant lymphocytic gastritis (LyG) is characterized by CD8+ T-cell infiltration of the stomach epithelium by a so far uncharacterized mechanism. Although Helicobacter pylori is typically undetectable in LyG, patients respond to H. pylori antibiotic eradication therapy, suggesting a non-H. pylori microbial trigger for the disease. Comparative microbiota analysis of specimens from LyG, H. pylori gastritis and healthy controls precluded involvement of H. pylori in LyG but identified Propionibacterium acnes as a possible disease trigger. In addition, the natural killer group 2 member D (NKG2D) system and the proinflammatory cytokine interleukin (IL)-15 are significantly upregulated in the gastric mucosa of LyG patients, and gastric epithelial cells respond to microbe-derived stimuli, including live P. acnes and the microbial products short-chain fatty acids, with induction of NKG2D ligands. In contrast, H. pylori infection does not activate or even repress NKG2D ligands. Together, our findings identify P. acnes as a possible causative agent for LyG, which is dependent on the NKG2D system and IL-15 activation. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.
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Gastritis/microbiología , Infecciones por Bacterias Grampositivas/inmunología , Células Asesinas Naturales/inmunología , Linfocitosis/microbiología , Propionibacterium acnes/aislamiento & purificación , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Biopsia , Estudios de Casos y Controles , Células Cultivadas , Niño , Femenino , Mucosa Gástrica/inmunología , Gastritis/inmunología , Gastritis/patología , Infecciones por Bacterias Grampositivas/patología , Helicobacter pylori/inmunología , Humanos , Inmunofenotipificación , Mediadores de Inflamación/metabolismo , Interleucina-15/biosíntesis , Interleucina-15/genética , Ligandos , Linfocitosis/inmunología , Masculino , Microbiota , Persona de Mediana Edad , Subfamilia K de Receptores Similares a Lectina de Células NK/metabolismo , Propionibacterium acnes/inmunología , ARN Mensajero/genética , Estómago/inmunología , Estómago/microbiología , Estómago/patología , Regulación hacia Arriba , Adulto JovenRESUMEN
Background: Helicobacter pylori (H. pylori) uses various strategies that attenuate mucosal immunity to ensure its persistence in the stomach. We recently found evidence that H. pylori might modulate the natural killer group 2, member 2 (NKG2D) system. The NKG2D receptor and its ligands are a major activation system of natural killer and cytotoxic T cells, which are important for mucosal immunity and tumor immunosurveillance. The NKG2D system allows recognition and elimination of infected and transformed cells, however viruses and cancers often subvert its activation. Here we aimed to identify a potential evasion of the NKG2D system in H. pylori infection. Methods: We analyzed expression of NKG2D system genes in gastric tissues of H. pylori gastritis and gastric cancer patients, and performed cell-culture based infection experiments using H. pylori isogenic mutants and epithelial and NK cell lines. Results: In biopsies of H. pylori gastritis patients, NKG2D receptor expression was reduced while NKG2D ligands accumulated in the lamina propria, suggesting NKG2D evasion. In vitro, H. pylori induced the transcription and proteolytic shedding of NKG2D ligands in stomach epithelial cells, and these effects were associated with specific H. pylori virulence factors. The H. pylori-driven release of soluble NKG2D ligands reduced the immunogenic visibility of infected cells and attenuated the cytotoxic activity of effector immune cells, specifically the anti-tumor activity of NK cells. Conclusion: H. pylori manipulates the NKG2D system. This so far unrecognized strategy of immune evasion by H. pylori could potentially facilitate chronic bacterial persistence and might also promote stomach cancer development by allowing transformed cells to escape immune recognition and grow unimpeded to overt malignancy.
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Gastritis , Infecciones por Helicobacter , Helicobacter pylori , Neoplasias Gástricas , Humanos , Subfamilia K de Receptores Similares a Lectina de Células NK/metabolismo , Evasión Inmune , Infecciones por Helicobacter/metabolismo , Células Asesinas Naturales , Neoplasias Gástricas/patología , Gastritis/metabolismo , Péptido Hidrolasas/metabolismoRESUMEN
The Klebsiella oxytoca species complex is part of the human microbiome, especially during infancy and childhood. K. oxytoca species complex strains can produce enterotoxins, namely, tilimycin and tilivalline, while also contributing to colonization resistance (CR). The relationship between these seemingly contradictory roles is not well understood. Here, by coupling ex vivo assays with CRISPR-mutagenesis and various mouse models, we show that K. oxytoca provides CR against Salmonella Typhimurium. In vitro, the antimicrobial activity against various Salmonella strains depended on tilimycin production and was induced by various simple carbohydrates. In vivo, CR against Salmonella depended on toxin production in germ-free mice, while it was largely toxin-independent in mice with residual microbiota. This was linked to the relative levels of toxin-inducing carbohydrates in vivo. Finally, dulcitol utilization was essential for toxin-independent CR in gnotobiotic mice. Together, this demonstrates that nutrient availability is key to both toxin-dependent and substrate-driven competition between K. oxytoca and Salmonella.
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Klebsiella oxytoca , Infecciones por Salmonella , Salmonella typhimurium , Klebsiella oxytoca/genética , Klebsiella oxytoca/metabolismo , Animales , Ratones , Infecciones por Salmonella/microbiología , Salmonella typhimurium/genética , Salmonella typhimurium/metabolismo , Salmonella typhimurium/crecimiento & desarrollo , Salmonella typhimurium/efectos de los fármacos , Humanos , Modelos Animales de Enfermedad , Enterotoxinas/metabolismo , Enterotoxinas/genética , Femenino , Ratones Endogámicos C57BL , Infecciones por Klebsiella/microbiología , Microbiota , Microbioma Gastrointestinal , Antibiosis , BenzodiazepinonasRESUMEN
Klebsiella oxytoca is a ubiquitous bacterium that is increasingly associated with inflammatory diseases. Here, we report the hybrid assembled genome for cytotoxic K. oxytoca strain AHC-6. The genome comprises a total of 5.7 Mbp, with a GC content of 55.2% and 5,258 coding sequences after assembly and annotation.
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[This corrects the article DOI: 10.3389/fmicb.2021.692453.].
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The DNA-alkylating metabolite tilimycin is a microbial genotoxin. Intestinal accumulation of tilimycin in individuals carrying til+ Klebsiella spp. causes apoptotic erosion of the epithelium and colitis. Renewal of the intestinal lining and response to injury requires the activities of stem cells located at the base of intestinal crypts. This study interrogates the consequences of tilimycin-induced DNA damage to cycling stem cells. We charted the spatial distribution and luminal quantities of til metabolites in Klebsiella-colonized mice in the context of a complex microbial community. Loss of marker gene G6pd function indicates genetic aberrations in colorectal stem cells that became stabilized in monoclonal mutant crypts. Mice colonized with tilimycin-producing Klebsiella displayed both higher frequencies of somatic mutation and more mutations per affected individual than animals carrying a non-producing mutant. Our findings imply that genotoxic til+ Klebsiella may drive somatic genetic change in the colon and increase disease susceptibility in human hosts.
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Microbiota , Mutágenos , Humanos , Ratones , Animales , Mutágenos/metabolismo , Colon/metabolismo , Mutación/genética , Células Madre , Mucosa IntestinalRESUMEN
Lewis (Le) antigens are fucosylated oligosaccharides present in the Helicobacter pylori lipopolysaccharide. Expression of these antigens is believed to be important for H. pylori colonization, since Le antigens also are expressed on the gastric epithelia in humans. A galactosyltransferase encoded by ß-(1,3)galT is essential for production of type 1 (Le(a) and Le(b)) antigens. The upstream gene jhp0562, which is present in many but not all H. pylori strains, is homologous to ß-(1,3)galT but is of unknown function. Because H. pylori demonstrates extensive intragenomic recombination, we hypothesized that these two genes could undergo DNA rearrangement. A PCR screen and subsequent sequence analyses revealed that the two genes can recombine at both the 5' and 3' ends. Chimeric ß-(1,3)galT-like alleles can restore function in a ß-(1,3)galT null mutant, but neither native nor recombinant jhp0562 can. Mutagenesis of jhp0562 revealed that it is essential for synthesis of both type 1 and type 2 Le antigens. Transcriptional analyses of both loci showed ß-(1,3)galT expression in all wild-type (WT) and mutant strains tested, whereas jhp0562 was not expressed in jhp0562 null mutants, as expected. Since jhp0562 unexpectedly displayed functions in both type 1 and type 2 Le synthesis, we asked whether galT, part of the type 2 synthesis pathway, had analogous functions in type 1 synthesis. Mutagenesis and complementation analysis confirmed that galT is essential for Le(b) production. In total, these results demonstrate that galT and jhp0562 have functions that cross the expected Le synthesis pathways and that jhp0562 provides a substrate for intragenomic recombination to generate diverse Le synthesis enzymes.
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Glicosiltransferasas/metabolismo , Helicobacter pylori/genética , Helicobacter pylori/inmunología , Lipopolisacáridos/biosíntesis , Lipopolisacáridos/inmunología , Secuencia de Aminoácidos , Secuencia de Bases , Prueba de Complementación Genética , Variación Genética , Genotipo , Glicosiltransferasas/genética , Helicobacter pylori/metabolismo , Antígenos del Grupo Sanguíneo de Lewis/biosíntesis , Antígenos del Grupo Sanguíneo de Lewis/inmunología , Lipopolisacáridos/química , Datos de Secuencia Molecular , Mutagénesis , Recombinación Genética , Alineación de Secuencia , Análisis de Secuencia de ADNRESUMEN
Bovine Genital Campylobacteriosis (BGC) is a worldwide spread venereal disease of cattle caused by Campylobacter fetus subsp. venerealis (Cfv). Although several real-time PCR assays were developed for Cfv identification, most target mobile genetic elements, which may lead to false-positive diagnosis. In this study, a real-time PCR assay coupled with High-Resolution Melting analysis (HRM) was developed for the identification of Campylobacter fetus subspecies and application in BGC diagnosis. Two HRM assays targeting different single nucleotide polymorphisms were validated using 51 C. fetus strains, including 36 Cfv and 15 C. fetus subsp. fetus (Cff). The specificity was assessed in 50 preputial samples previously tested as negative for C. fetus and in 24 strains from other Campylobacter species. The analytical sensitivity was determined with ten-fold dilutions of Cfv genome copies and in preputial samples spiked with Cfv cells. Both HRM assays accurately identified the 51 C. fetus strains, showing 100% concordance with the previous identification. C. fetus subspecies identification by HRM showed concordant results with the glycine test in 98.0% of the isolates. No amplification was obtained in C. fetus negative preputial samples as well as in strains from other Campylobacter species. The assays were able to detect 102 genome copies of Cfv, while for preputial washing samples the limit of detection was 103 CFU/mL. These novel HRM assays represent a highly specific and sensitive tool for the identification of C. fetus subspecies and show potential for direct use in bull preputial samples for BGC diagnosis.
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OBJECTIVE: Toxin-producing Klebsiella oxytoca causes antibiotic-associated haemorrhagic colitis (AAHC). The disease-relevant cytotoxins tilivalline and tilimycine produced by certain K. oxytoca isolates are encoded by the non-ribosomal peptide synthetase genes A (npsA) and B (npsB). In this study, the new LightMix® Modular kit for the detection of relevant K. oxytoca sensu lato (s.l.) toxin genes was evaluated. METHODS: DNA was extracted on the automated EMAG® platform. Amplification was done on the Light Cycler® 480 II instrument. In total, 130 residual faecal specimens collected from patients with antibiotic-associated diarrhoea were studied to determine the clinical sensitivity and specificity. Toxigenic culture served as reference method. RESULTS: With the new kit, the limit of detection was 15 CFU/mL for all targets. For the pehX target specific to K. oxytoca s.l., 65 of 130 clinical specimens were positive, while toxin-specific targets (npsA/npsB) were positive in 47 of 130. The npsA/npsB PCR targets showed a clinical sensitivity of 100% (95%CI 80.5-100%) and a specificity of 73.5% (95%CI 64.3-81.3%) with a positive predictive value of 16.5% (95%CI 12.7-21.2%) and a negative predictive value of 100%. CONCLUSION: Compared with culture, additional clinical specimens positive for K. oxytoca s.l. were detected with real-time PCR. The specificity of the toxin targets appears moderate due to the inferior sensitivity of the culture-based reference method. Since the developed assay is highly sensitive, it may be used as first-line method to improve the diagnosis of AAHC.
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Colitis , Enterocolitis Seudomembranosa , Infecciones por Klebsiella , Antibacterianos/uso terapéutico , Colitis/complicaciones , Colitis/diagnóstico , Colitis/tratamiento farmacológico , Enterocolitis Seudomembranosa/tratamiento farmacológico , Hemorragia , Humanos , Infecciones por Klebsiella/microbiología , Klebsiella oxytoca/genética , Reacción en Cadena en Tiempo Real de la PolimerasaRESUMEN
Klebsiella spp. that secrete the DNA-alkylating enterotoxin tilimycin colonize the human intestinal tract. Numbers of toxigenic bacteria increase during antibiotic use, and the resulting accumulation of tilimycin in the intestinal lumen damages the epithelium via genetic instability and apoptosis. Here we examine the impact of this genotoxin on the gut ecosystem. 16S rRNA sequencing of faecal samples from mice colonized with Klebsiella oxytoca strains and mechanistic analyses show that tilimycin is a pro-mutagenic antibiotic affecting multiple phyla. Transient synthesis of tilimycin in the murine gut antagonized niche competitors, reduced microbial richness and altered taxonomic composition of the microbiota both during and following exposure. Moreover, tilimycin secretion increased rates of mutagenesis in co-resident opportunistic pathogens such as Klebsiella pneumoniae and Escherichia coli, as shown by de novo acquisition of antibiotic resistance. We conclude that tilimycin is a bacterial mutagen, and flares of genotoxic Klebsiella have the potential to drive the emergence of resistance, destabilize the gut microbiota and shape its evolutionary trajectory.
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Enterotoxinas , Klebsiella , Animales , Humanos , Ratones , Antibacterianos/farmacología , Farmacorresistencia Microbiana , Ecosistema , Escherichia coli/genética , Klebsiella/genética , ARN Ribosómico 16S/genética , Microbioma GastrointestinalRESUMEN
Gastrointestinal microbes respond to biochemical metabolites that coordinate their behaviors. Here, we demonstrate that bacterial indole functions as a multifactorial mitigator of Klebsiella grimontii and Klebsiella oxytoca pathogenicity. These closely related microbes produce the enterotoxins tilimycin and tilivalline; cytotoxin-producing strains are the causative agent of antibiotic-associated hemorrhagic colitis and have been associated with necrotizing enterocolitis of premature infants. We demonstrate that carbohydrates induce cytotoxin synthesis while concurrently repressing indole biosynthesis. Conversely, indole represses cytotoxin production. In both cases, the alterations stemmed from differential transcription of npsA and npsB, key genes involved in tilimycin biosynthesis. Indole also enhances conversion of tilimycin to tilivalline, an indole analog with reduced cytotoxicity. In this context, we established that tilivalline, but not tilimycin, is a strong agonist of pregnane X receptor (PXR), a master regulator of xenobiotic detoxification and intestinal inflammation. Tilivalline binding upregulated PXR-responsive detoxifying genes and inhibited tubulin-directed toxicity. Bacterial indole, therefore, acts in a multifunctional manner to mitigate cytotoxicity by Klebsiella spp.: suppression of toxin production, enhanced conversion of tilimycin to tilivalline, and activation of PXR. IMPORTANCE The human gut harbors a complex community of microbes, including several species and strains that could be commensals or pathogens depending on context. The specific environmental conditions under which a resident microbe changes its relationship with a host and adopts pathogenic behaviors, in many cases, remain poorly understood. Here, we describe a novel communication network involving the regulation of K. grimontii and K. oxytoca enterotoxicity. Bacterial indole was identified as a central modulator of these colitogenic microbes by suppressing bacterial toxin (tilimycin) synthesis and converting tilimycin to tilivalline while simultaneously activating a host receptor, PXR, as a means of mitigating tissue cytotoxicity. On the other hand, fermentable carbohydrates were found to inhibit indole biosynthesis and enhance toxin production. This integrated network involving microbial, host, and metabolic factors provides a contextual framework to better understand K. oxytoca complex pathogenicity.
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Enterocolitis Seudomembranosa , Infecciones por Klebsiella , Humanos , Recién Nacido , Klebsiella oxytoca/genética , Klebsiella oxytoca/metabolismo , Enterotoxinas/metabolismo , Enterocolitis Seudomembranosa/microbiología , Infecciones por Klebsiella/microbiología , Citotoxinas/metabolismo , Indoles/metabolismoRESUMEN
We report here the first demonstration of intra- and interspecies conjugative plasmid DNA transfer for Campylobacter fetus. Gene regions carried by a Campylobacter coli plasmid were identified that are sufficient for conjugative mobilization to Escherichia coli and C. fetus recipients. A broader functional range is predicted. Efficient DNA transfer involves the virB9 and virD4 genes of the type IV bacterial secretion system encoded by a pathogenicity island of C. fetus subsp. venerealis. Complementation of these phenotypes from expression constructions based on the promoter of the C. fetus surface antigen protein (sap) locus was temperature dependent, and a temperature regulation of the sap promoter was subsequently confirmed under laboratory conditions. Gene transfer was sensitive to surface or entry exclusion functions in potential recipient cells carrying IncPα plasmid RP4 implying functional relatedness to C. fetus proteins. The virB/virD4 locus is also known to be involved in bacterial invasion and killing of cultured human cells in vitro. Whether specifically secreted effector proteins contribute to host colonization and infection activities is currently unknown. Two putative effector proteins carrying an FIC domain conserved in a few bacterial type III and type IV secreted proteins of pathogens were analyzed for secretion by the C. fetus or heterologous conjugative systems. No evidence for interbacterial translocation of the Fic proteins was found.
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Campylobacter fetus/metabolismo , Extensiones de la Superficie Celular/metabolismo , Sustancias Macromoleculares/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Campylobacter fetus/genética , Conjugación Genética , ADN Bacteriano/química , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica , Genes Bacterianos , Islas Genómicas , Datos de Secuencia Molecular , Plásmidos , Análisis de Secuencia de ADN , TemperaturaRESUMEN
Members of the Klebsiella oxytoca species complex (KoSC) are emerging human pathogens causing infections of increasing significance especially in healthcare settings. KoSC strains are affiliated with distinct phylogroups based on genetic variation at the beta-lactamase gene (bla OXY) and it has been proposed that each major phylogroup represents a unique species. However, since the typing methods applied in clinical settings cannot differentiate every species within the complex, existing clinical, epidemiological and DNA sequence data is frequently misclassified. Here we systematically examined the phylogenetic relationship of KoSC strains to evaluate robustness of existing typing methods and to provide a simple typing strategy for KoSC members that cannot be differentiated biochemically. Initial analysis of a collection of K. oxytoca, K. michiganensis, K. pasteurii, and K. grimontii strains of environmental origin showed robust correlation of core phylogeny and blaOXY grouping. Moreover, we identified species-specific accessory gene loci for these strains. Extension of species correlation using database entries initially failed. However, assessment of average nucleotide identities (ANI) and phylogenetic validations showed that nearly one third of isolates in public databases have been misidentified. Reclassification resulted in a robust reference strain set for reliable species identification of new isolates or for retyping of strains previously analyzed by multi-locus sequence typing (MLST). Finally, we show convergence of ANI, core gene phylogeny, and accessory gene content for available KoSC genomes. We conclude that also the monophyletic members K. oxytoca, K. michiganensis, K. pasteurii and K. grimontii can be simply differentiated by a PCR strategy targeting bla OXY and accessory genes defined here.
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The pathogen Campylobacter fetus comprises two subspecies, C. fetus subsp. fetus and C. fetus subsp. venerealis. Although these taxa are highly related on the genome level, they are adapted to distinct hosts and tissues. C. fetus subsp. fetus infects a diversity of hosts, including humans, and colonizes the gastrointestinal tract. In contrast, C. fetus subsp. venerealis is largely restricted to the bovine genital tract, causing epidemic abortion in these animals. In light of their close genetic relatedness, the specific niche preferences make the C. fetus subspecies an ideal model system to investigate the molecular basis of host adaptation. In this study, a subtractive-hybridization approach was applied to the genomes of the subspecies to identify different genes potentially underlying this specificity. The comparison revealed a genomic island uniquely present in C. fetus subsp. venerealis that harbors several genes indicative of horizontal transfer and that encodes the core components necessary for bacterial type IV secretion. Macromolecular transporters of this type deliver effector molecules to host cells, thereby contributing to virulence in various pathogens. Mutational inactivation of the putative secretion system confirmed its involvement in the pathogenicity of C. fetus subsp. venerealis.
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Campylobacter fetus/genética , Campylobacter fetus/patogenicidad , Islas Genómicas/fisiología , Virulencia/fisiología , Análisis del Polimorfismo de Longitud de Fragmentos Amplificados , Proteínas Bacterianas/genética , Proteínas Bacterianas/fisiología , Células CACO-2 , Infecciones por Campylobacter/genética , Electroforesis en Gel de Campo Pulsado , Genoma Bacteriano/genética , Genoma Bacteriano/fisiología , Islas Genómicas/genética , Células HeLa , Humanos , Datos de Secuencia Molecular , Sistemas de Lectura Abierta/genética , Plásmidos/genética , Reacción en Cadena de la Polimerasa , Análisis de Secuencia de ADN , Virulencia/genéticaRESUMEN
Microbial induced concrete corrosion (MICC) is recognized as one of the main degradation mechanisms of subsurface infrastructure worldwide, raising the demand for sustainable construction materials in corrosive environments. This review aims to summarize the key research progress acquired during the last decade regarding the understanding of MICC reaction mechanisms and the development of durable materials from an interdisciplinary perspective. Special focus was laid on aspects governing concrete - micoorganisms interaction since being the central process steering biogenic acid corrosion. The insufficient knowledge regarding the latter is proposed as a central reason for insufficient progress in tailored material development for aggressive wastewater systems. To date no cement-based material exists, suitable to withstand the aggressive conditions related to MICC over its entire service life. Research is in particular needed on the impact of physiochemical material parameters on microbial community structure, growth characteristics and limitations within individual concrete speciation. Herein an interdisciplinary approach is presented by combining results from material sciences, microbiology, mineralogy and hydrochemistry to stimulate the development of novel and sustainable materials and mitigation strategies for MICC. For instance, the application of antibacteriostatic agents is introduced as an effective instrument to limit microbial growth on concrete surfaces in aggressive sewer environments. Additionally, geopolymer concretes are introduced as highly resistent in acid environments, thus representing a possible green alternative to conventional cement-based construction materials.