Project description:Young adult fer-15;fem-1 Caenorhabditis elegans were infected with Staphylococcus aureus for 8 h to determine the transcriptional host response to Staphylococcus aureus. Analysis of differential gene expression in C. elegans young adults exposed to two different bacteria: E. coli strain OP50 (control), wild-type Staphylococcus aureus RN6390. Samples were analyzed at 8 hours after exposure to the different bacteria. These studies identified C. elegans genes induced by pathogen infection. Keywords: response to pathogen infection, innate immunity, host-pathogen interactions
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:Analysis of transcriptional profiles in whole blood from patients with Staphylococcus aureus infection. The hypothesis tested is that transcriptional profile heterogeneity will reflect patient clinical heterogeneity.
Project description:Infection in diabetic foot ulcers (DFU) are one of the major complications associated with diabetic patients. Staphylococcus aureus is the most common offending pathogen in patients with infected DFU. Previous studies have suggested application of species-specific antibodies against S. aureus for diagnosis and monitoring treatment response. Early and accurate identification of the main pathogen is critical for management of DFU infection. Understanding the host immune response against species-specific infection may facilitate diagnosis and suggest potential intervention options to promote healing infected DFUs. We sought to investigate evolving host transcriptome associated with surgical treatment of S. aureus infected DFU. This study compared the transcriptome profile of twenty-one patients with S. aureus infected DFU who underwent initial foot salvage therapy with irrigation and debridement followed by intravenous antibiotics therapy. Blood samples were collected at the recruitment (0-weeks) and 8-week after therapy to isolate peripheral blood mononuclear cells (PBMC). We analyzed the PBMCs expression of transcriptomes at two different time points (0 vs 8-week). Subjects were further divided into two groups at 8-week: healed (n=17, 80.95%) versus non-healed (n=4,19.05%) based on the wound healing status. DESeq2 differential gene analysis was performed. An increased expression of IGHG1, IGHG2, IGHG3 and IGLV3-21, IGLV6-57 were noted during active infection at 0-week compared to 8-week. Lysine and arginine-rich histones (HIST1H2AJ, HIST1H2AL, HIST1H2BM, HIST1H3B and HIST1H3G) were upregulated at the initial phase of active infection at 0-week. CD177 and RRM2 were also upregulated at the initial phase of active infection (0-week) compared to 8-week follow-up. Genes of heat shock protein members (HSPA1A, HSPE1, and HSP90B1) were high in not-healed compared to healed patients 8-week after therapy. The outcome of our study suggests that identification of genes evolution based on a transcriptomic profiling could be a useful tool for diagnosing infection, assessing severity and assess host-immune response to therapies.
Project description:Therapy of Staphylococcus aureus bacteremia is often ineffective, even under optimal conditions, and adapted subclones with attenuated agr-mediated virulence activation are associated with persistent infection and mortality. To understand how apparent loss of virulence leads to increased mortality, we sequenced complete genomes from clone pairs from colonizing and infected sites of patients in whom S. aureus demonstrated a within-host downshift in agr function in the infecting isolate. Clone pairs with a downshift in agr function showed substantial genetic divergence compared to wild-type pairs from controls. Complementation studies further identified an agr-defective bacteremic strain that was highly virulent in vivo, which we linked to a mutation that restored expression of the agr-regulated ess/Type-VII secretion system; a known virulence factor. Our results suggest that selection pressure during invasive infection is strong enough to mutationally bypass agr-deficiency associated loss of virulence, and that efforts to suppress agr function may need to be reconsidered.
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:Methicillin resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen chief amongst bloodstream infecting pathogens. MRSA produces an array of human specific virulence factors that may contribute to immune suppression. Here, we defined the response of primary human phagocytes to infection with MRSA using RNA-Seq. We found that the overall transcriptional response to MRSA was weak both in the number of genes and the magnitude of response. Using an ex vivo bacteremia model with fresh human blood, we found that infection with live MRSA resulted in the down-regulation of genes related to innate immune response, and cytokine and chemokine signaling. This muted transcriptional response was conserved across diverse S. aureus clones but absent in heat-killed MRSA or blood infected with live Staphylococcus epidermidis. Importantly, the muted signature was also present in patients with S. aureus bacteremia. We next identified the master regulator SaeRS and the SaeRS-regulated pore-forming toxins as key mediators of transcriptional suppression. The impaired chemokine and cytokine responses were reflected by circulating protein levels in the plasma. MRSA elicits a soluble milieu that is restrictive in the recruitment of human neutrophils compared to strains lacking saeRS. Thus, MRSA blunts the inflammatory response resulting in impaired neutrophil recruitment, which could promote the survival of S. aureus during invasive infection.
Project description:Mastitis in dairy cattle can result from infection by a range of microorganisms but is principally caused by coliform bacteria and gram positive bacteria such as Staphylococcus aureus (S. aureus). The former species are often acquired by environmental contamination while S. aureus is particularly problematic due to its resistance to antibiotic treatments and ability to reside within mammary tissue in a chronic, subclinical state. The transcriptional and translational responses within bovine mammary epithelial tissue subjected to intramammary challenge with S. aureus are poorly characterised, particularly at the earliest stages of infection. A Bovine Innate Immune Microarray was employed to measure changes in gene expression occurring in bovine mammary tissues sampled from three dairy cows after a brief and graded intramammary challenge with a virulent strain of S. aureus. Keywords: dose response, disease state analysis Animal infected with vaying doses of S. aureus in different udder locations were compared to a single control uninfected tissue and to the other 2 locations at each infective dose. Dye swaps were performed for each comparison.