Project description:We analysed the gene expression profiles after infection of Staphylococcus aureus at ZT4 in CXCL14-KO mice. The group of genes categolized as GO defense response (GO: 006952) were upregulated upon a response to Staphylococcus aureus infection. The expression of IL1b, Cxcl2, and Ccl3 were significantly suppressed in infected ear of Cxcl14-KO compared to that of WT.
Project description:Although it has recently been shown that A/J mice are highly susceptible to Staphylococcus aureus sepsis as compared to C57BL/6J, the specific genes responsible for this differential phenotype are unknown. Using chromosome substitution strains (CSS), we found that factors on chromosomes (chr) 8, 11, and 18 are responsible for susceptibility to S. aureus sepsis in A/J mice. F1 mice from C57BL/6J X CSS8 cross (C8A) and C57BL/6J X CSS18 (C18A) were also susceptible to S. aureus (median survival < 48 h), whereas F1 mice from C57BL/6J X CSS11 cross (C11A) were resistant (median survival > 120 h) to S. aureus. Bacterial loads in the kidney were consistent with F1 median survivals, with higher bacterial counts in susceptible mice. No sexlinked associations with susceptibility were noted in F1 intercrosses. Using whole genome transcription profiling, we identified a total of 192 genes on chromosomes 8, 11, and 18 which are differentially expressed between A/J and C57BL/6J in the setting of S. aureus infection. Of these, 28 genes had Gene Ontology annotations indicating a potential immune response function. These 28 genes are associated with susceptibility to S. aureus in A/J mice, and are potential determinants of susceptibility to S. aureus infection in humans. To identify genes for which differential expression between A/J and C57BL/6J mice could contribute to host susceptibility to S. aureus infection, we compared the gene expression profiles between uninfected A/J and C57BL/6J mice and between infected A/J and C57BL/6J mice at 2, 4, 6, and 12 hours after infection.
Project description:Background: Staphylococcus aureus is a major pathogen of humans and animals and rapidly emerging antibiotic-resistant strains have further increased the severity of this health issue. Host genetics influence susceptibility to S. aureus infections, and genes determining infection outcome should be identified to analyze immune-based therapies as an alternative to antibiotics. Here, we used outbred animals from a divergent selection on susceptibility towards Staphylococcus infection to explore host immunogenetics. Methodology/Principal Findings: We investigated how dendritic cells respond to heat-inactivated S. aureus and whether dendritic cells from animals with different degree of susceptibility have distinct gene expression profiles. We measured expression levels of 15K probes from in vitro S. aureus-stimulated bone marrow-derived dendritic cells at three different time points (0, 3 and 8 hours) by using Agilent microarrays. Furthermore, a selected number of genes were confirmed by RT-qPCR. Gene signatures of stimulated DCs were obtained and genes involved in inflammatory process and T helper cell polarization were highly up regulated upon stimulation. Moreover, a set of 204 genes were statistically different between susceptible and resistant animals, and grouped them according to their predisposition to staphylococcal infection. Interestingly, a role of classical pathway of Complement and early regulation of inflammation is observed in the resistant line through over expression of C1q and Ido1 genes respectively. On the opposite, over expression of genes in the IL1R pathway in the susceptible animals was noticed. Furthermore, leucocyte extravasation pathway was also found dominant in the susceptible line. Conclusion/Significance: we successfully obtained Staphylococcus aureus associated gene expression of ovine BM-DC in 8 hour kinetics experiment. Distinct transcriptional profiles of dendritic cells obtained from resistant and susceptible lines may explain susceptibility towards S. aureus infections in a broad context. Keywords: Staphylococcus aureus, dendritic cells, mammalian, transcriptome, immunity, mastitis 44 sample records; two-colour dye-swap experimental design
Project description:Staphylococcus aureus causes a spectrum of human infection. Diagnostic delays and uncertainty lead to treatment delays and inappropriate antibiotic use. A growing literature suggests the host’s inflammatory response to the pathogen represents a potential tool to improve upon current diagnostics. The hypothesis of this study is that the host responds differently to S. aureus than to E. coli infection in a quantifiable way, providing a new diagnostic avenue. This study uses Bayesian sparse factor modeling and penalized binary regression to define peripheral blood gene-expression classifiers of murine and human S. aureus infection. The murine-derived classifier distinguished S. aureus infection from healthy controls and Escherichia coli-infected mice across a range of conditions (mouse and bacterial strain, time post infection) and was validated in outbred mice (AUC>0.97). A S. aureus classifier derived from a cohort of 95 human subjects distinguished S. aureus blood stream infection (BSI) from healthy subjects (AUC 0.99) and E. coli BSI (AUC 0.82). Murine and human responses to S. aureus infection share common biological pathways, allowing the murine model to classify S. aureus BSI in humans (AUC 0.84). Both murine and human S. aureus classifiers were validated in an independent human cohort (AUC 0.95 and 0.94, respectively). The approach described here lends insight into the conserved and disparate pathways utilized by mice and humans in response to these infections. Furthermore, this study advances our understanding of S. aureus infection; the host response to it; and identifies new diagnostic and therapeutic avenues.
Project description:Staphylococcus aureus is a significant cause of human infection. Here, we demonstrate that mutations in the transcriptional repressor of purine biosynthesis, purR, enhance the pathogenic potential of S. aureus. Indeed, systemic infection with purR mutants causes accelerated mortality in mice, which is due to aberrant up-regulation of fibronectin binding proteins (FnBPs). Remarkably, purR mutations can arise upon exposure of S. aureus to stress, such as an intact immune system. In humans, naturally occurring anti-FnBP antibodies exist that, while not protective against recurrent S. aureus infection, ostensibly protect against hypervirulent S. aureus infections. Vaccination studies support this notion, where anti-Fnb antibodies in mice protect against purR hypervirulence. These findings provide a novel link between purine metabolism and virulence in S. aureus.
Project description:Background: Staphylococcus aureus is a major pathogen of humans and animals and rapidly emerging antibiotic-resistant strains have further increased the severity of this health issue. Host genetics influence susceptibility to S. aureus infections, and genes determining infection outcome should be identified to analyze immune-based therapies as an alternative to antibiotics. Here, we used outbred animals from a divergent selection on susceptibility towards Staphylococcus infection to explore host immunogenetics. Methodology/Principal Findings: We investigated how dendritic cells respond to heat-inactivated S. aureus and whether dendritic cells from animals with different degree of susceptibility have distinct gene expression profiles. We measured expression levels of 15K probes from in vitro S. aureus-stimulated bone marrow-derived dendritic cells at three different time points (0, 3 and 8 hours) by using Agilent microarrays. Furthermore, a selected number of genes were confirmed by RT-qPCR. Gene signatures of stimulated DCs were obtained and genes involved in inflammatory process and T helper cell polarization were highly up regulated upon stimulation. Moreover, a set of 204 genes were statistically different between susceptible and resistant animals, and grouped them according to their predisposition to staphylococcal infection. Interestingly, a role of classical pathway of Complement and early regulation of inflammation is observed in the resistant line through over expression of C1q and Ido1 genes respectively. On the opposite, over expression of genes in the IL1R pathway in the susceptible animals was noticed. Furthermore, leucocyte extravasation pathway was also found dominant in the susceptible line. Conclusion/Significance: we successfully obtained Staphylococcus aureus associated gene expression of ovine BM-DC in 8 hour kinetics experiment. Distinct transcriptional profiles of dendritic cells obtained from resistant and susceptible lines may explain susceptibility towards S. aureus infections in a broad context. Keywords: Staphylococcus aureus, dendritic cells, mammalian, transcriptome, immunity, mastitis
Project description:Staphylococcus aureus causes a spectrum of human infection. Diagnostic delays and uncertainty lead to treatment delays and inappropriate antibiotic use. A growing literature suggests the hostM-bM-^@M-^Ys inflammatory response to the pathogen represents a potential tool to improve upon current diagnostics. The hypothesis of this study is that the host responds differently to S. aureus than to E. coli infection in a quantifiable way, providing a new diagnostic avenue. This study uses Bayesian sparse factor modeling and penalized binary regression to define peripheral blood gene-expression classifiers of murine and human S. aureus infection. The murine-derived classifier distinguished S. aureus infection from healthy controls and Escherichia coli-infected mice across a range of conditions (mouse and bacterial strain, time post infection) and was validated in outbred mice (AUC>0.97). A S. aureus classifier derived from a cohort of 95 human subjects distinguished S. aureus blood stream infection (BSI) from healthy subjects (AUC 0.99) and E. coli BSI (AUC 0.82). Murine and human responses to S. aureus infection share common biological pathways, allowing the murine model to classify S. aureus BSI in humans (AUC 0.84). Both murine and human S. aureus classifiers were validated in an independent human cohort (AUC 0.95 and 0.94, respectively). The approach described here lends insight into the conserved and disparate pathways utilized by mice and humans in response to these infections. Furthermore, this study advances our understanding of S. aureus infection; the host response to it; and identifies new diagnostic and therapeutic avenues. To create a host gene expression-based classifier for S. aureus infection, mice from a variety of experimental conditions were utilized. Seven different strains of inbred mice (n=187 total) were challenged with four different S. aureus strains via intraperitoneal inoculation and sacrificed at various time points as described in Methods. The comparator group for model derivation included 50 A/J or C57BL/6J mice inoculated with E. coli (O18:K1:H7) as well as 54 uninfected mice. Next, the murine S. aureus classifier was externally validated in outbred CD-1 mice with S. aureus infection (Sanger 476 or USA300), E. coli infection (O18:K1:H7), or uninfected controls (10 animals per condition). Method: All experiments were performed on mice 6-8 weeks old. For the murine S. aureus predictor, seven inbred mouse strains (3 mice/strain: 129S1/SvImJ, A/J, AKR/J, BALB/cByJ, C57BL/6J, C3H/HeJ, and NOD/LtJ) were IP inoculated with 107 CFU/g of S. aureus Sanger476, euthanized at 2h after injection, and bled. This was repeated using four different S. aureus strains (USA100, USA300, MW2, and Sanger476) in A/J mice (n=3 per S. aureus strain). For time series experiments, both A/J and C57BL/6J mouse strains were IP inoculated with S. aureus Sanger476 as above, and sacrificed at 2, 4, 6, and 12h after injection (n=5 per time point).
Project description:Staphylococcus aureus (S. aureus) is an important human and animal pathogen, multiply resistant strains are increasingly widespread, new agents are needed for the treatment of S. aureus. magnolol has potent antimicrobial activity against S. aureus. We employed Affymetrix Staphylococcus aureus GeneChipsTM arrays to investigate the global transcriptional profiling of Staphylococcus aureus ATCC25923 treated with magnolol. Keywords: gene expression array-based, count