Unknown,Transcriptomics,Genomics,Proteomics

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Biomarker-based classification of bacterial and fungal whole-blood infections in a genome-wide expression study

ABSTRACT: Sepsis is a clinical syndrome that can be caused by bacteria or fungi. Early knowledge on the nature of the causative agent is a prerequisite for targeted anti-microbial therapy. Besides currently used detection methods like blood culture and PCR-based assays, the analysis of the transcriptional response of the host to infecting organisms holds great promise. In this study, we aim to examine the transcriptional footprint of infections caused by the bacterial pathogens Staphylococcus aureus and Escherichia coli and the fungal pathogens Candida albicans and Aspergillus fumigatus in a human whole-blood model. Moreover, we use the expression information to build a random forest classifier to determine if the pathogen is bacterial, fungal or neither of the two. After normalizing the transcription intensities using stably expressed reference genes, we filtered the gene set for biomarkers of bacterial or fungal blood infections. This selection is based on differential expression and an additional gene relevance measure. In this way, we identified 38 biomarker genes, including IL6, SOCS3, and IRG1 which were already associated to sepsis by other studies. Using these genes, we trained the classifier and assessed its performance. It yielded a 96% accuracy (sensitivities >93%, specificities >97%) for a 10-fold stratified cross-validation and a 92% accuracy (sensitivities and specificities >83%) for an additional dataset comprising Cryptococcus neoformans infections. Furthermore, the noise-robustness of the classifier suggests high rates of correct class predictions on datasets of new species. In conclusion, this genome-wide approach demonstrates an effective feature selection process in combination with the construction of a well-performing classification model. Further analyses of genes with pathogen-dependent expression patterns can provide insights into the systemic host responses, which may lead to new anti-microbial therapeutic advances. Analysis of innate immune activation on the basis of gene expression of whole blood cells during ex vivo whole blood infection with bacterial (Staphylococcus aureus, Escherichia coli) and fungal pathogens (Candida albicans, Aspergillus fumigatus) in comparison to mock-treated blood.

ORGANISM(S): Homo sapiens

SUBMITTER: Andreas Dix

PROVIDER: E-GEOD-65088 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: The role of viral infections as a mediator of systemic immune dysfunction leading to sepsis has received limited attention compared to the bacterial pathogens. The COVID-19 pandemic and the increased cases of sepsis in the absence of known bacterial pathogens have highlighted the clinical relevance of viruses as causative agents of sepsis. In this study, we investigated clinical, laboratory, proteomic, and metabolic characteristics to shed light on the molecular mechanisms underlying the pathological conditions of viral sepsis in COVID-19. Methods: We retrospectively analyzed data from 231 hospitalized patients with confirmed COVID-19 admitted to three hospitals in China. The presence of viral sepsis was diagnosed with SOFA score 2 in the absence of bacterial infection. Demographics, clinical, and laboratory parameters, as well as clinical outcomes, were obtained from electronic chart reviews. Plasma samples were obtained from a subset of these patients (23 patients in the Viral Non-Sepsis [VNS] group and 14 patients in the Viral Sepsis [VS] group) to analyze proteomic and metabolic profiles. Findings: The viral sepsis group exhibited severe disease, as indicated by elevated markers of both pulmonary (ARDS) and systemic disease (liver, kidney, and cardiac injury). Consistent with known immune paralysis observed in sepsis, subjects with viral sepsis were more susceptible to secondary infections by bacterial and fungal pathogens. Overall, viral sepsis led to an increased length of ICU stay, required invasive mechanical ventilation and a significant increase in mortality compared to the non-viral sepsis group. At the molecular levels, we identified unique metabolic and proteomic signatures that suggest a substantial contribution of the coagulation and platelet dysfunction pathways to systemic pathologies. Interpretation: Viral sepsis presents an underrecognized threat contributing to high mortality. Specific metabolic and proteomic changes demonstrated coagulation and platelet dysfunction as key pathological pathway in viral sepsis.

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Biomarker-based classification of bacterial and fungal whole-blood infections in a genome-wide expression study

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