Project description:Methicillin-resistant Staphylococcus aureus (MRSA) infections result in more than 200,000 hospitalizations and 10,000 deaths in the United States each year and remain an important medical challenge. To better understand the transcriptome of Staphylococcus aureus USA300 NRS384, a community-acquired MRSA strain, we have conducted an RNA-Seq experiment on WT samples.
Project description:To explore the Spermine(Spm)-based antibacterial targets in S. aureus, time course-dependent transcriptome analysis was conducted on Mu50 (MRSA) in the absence and presence of Spm.
Project description:Staphylococcus aureus can cause serious skin, respiratory, and other life-threatening invasive infections in humans, and methicillin-resistant S. aureus (MRSA) strains have been acquiring increasing antibiotic resistance. While MRSA was once mainly considered a hospital-acquired infection, the emergence of new strains, some of which are pandemic, has resulted in community-acquired MRSA infections that often present as serious skin infections in otherwise healthy individuals. Accordingly, defining the mechanisms that govern the activation and regulation of the immune response to MRSA is clinically important and could lead to the discovery of much needed rational targets for therapeutic intervention. Because the cytokine thymic stromal lymphopoetin (TSLP) is highly expressed by keratinocytes of the skin3, we investigated its role in host-defense against MRSA. Here we demonstrate that TSLP acts on neutrophils to increase their killing of MRSA. In particular, we show that both mouse and human neutrophils express functional TSLP receptors. Strikingly, TSLP enhances mouse neutrophil killing of MRSA in both an in vitro whole blood killing assay and an in vivo skin infection model. Similarly, TSLP acts directly on purified human blood neutrophils to reduce MRSA burden. Unexpectedly, we demonstrate that TSLP mediates these effects both in vivo and in vitro by engaging the complement C5 system. Thus, TSLP increases MRSA killing in a neutrophil- and complement-dependent manner, revealing a key connection between TSLP and the innate complement system, with potentially important therapeutic implications for control of MRSA infection.
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) is a major hospital- and community-acquired pathogen, but the mechanisms underlying host-defense to MRSA remain poorly understood. Here, we investigated the role of IL-21 in this process. When administered intra-tracheally into wild-type mice, IL-21 induced granzymes and augmented clearance of pulmonary MRSA but not when neutrophils were depleted or a granzyme B inhibitor was added. Correspondingly, IL-21 induced MRSA killing by human peripheral blood neutrophils. Unexpectedly, however, basal MRSA clearance was enhanced when IL-21 signaling was blocked, both in Il21r KO mice and in wild-type mice injected with IL-21R-Fc fusion-protein. This correlated with increased type I interferon and an IFN-related gene signature, and indeed anti-IFNAR1 treatment diminished MRSA clearance in these animals. Moreover, we found that IFNβ induced granzyme B and promoted MRSA clearance in a granzyme B-dependent fashion. These results reveal an interplay between IL-21 and type-I IFN in the innate immune response to MRSA.
Project description:To investigate the function NarGHJI in the regulation of the expression of virulence factors, we constructed a narGHJI mutant by targeted deletion of narG in MRSA isolate USA300 LAC We then performed gene expression profiling analysis using data obtained from RNA-seq of of two different strains at early exponential (OD600 = 0.5).
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) infections result in more than 200,000 hospitalizations and 10,000 deaths in the United States each year and remain an important medical challenge. A key factor of S. aureus pathogenesis is the production of virulence proteins that are secreted into the extracellular matrix damaging host tissues and forming abscesses that may serve as replicative niches for the bacteria. We recently discovered that host-derived cis-unsaturated fatty acids activate the transcription and translation of EsxA, a protein that plays a central role in abscess formation in clinically relevant MRSA strains. Additionally, we discovered that fatty acid stimulation of EsxA is dependent on fakA, a gene that encodes a protein responsible for the incorporation of exogenous fatty acids into the S. aureus phospholipid membrane. In order to gain a comprehensive understanding of host-fatty-acid-sensing in S. aureus, we performed RNA-Seq analysis on WT Staphylococcus aureus USA300 NRS384, a community-acquired MRSA strain, in the presence and absence of 10μM linoleic acid.
Project description:Staphylococcus aureus has been recognized as an important cause of human disease for more than 100 years. Resistance to multiple classes of antibiotics is becoming an increasingly difficult problem in the management of methicillin-resistant S. aureus (MRSA) and vancomycin-intermediate resistant S. aureus (VISA) infections. One approach to the MRSA and VISA problem, involves the discovery and development of new natural antimicrobials. The antimicrobial properties of essential oils of plant origin have been recognized for many years. In this study 0.1% of commercial cold pressed terpeneless Valencia orange oil (CPV) showed inhibitory and lytic activity against MRSA and VISA. To identify the mechanisms of action of CPV genomic response of CPV treated MRSA was analyzed by transcriptional profiling. Results showed alteration in the expression of cell wall peptidoglycan biosynthesis associated genes in the CPV treated cells. Transmission electron microscopic observation of CPV treated MRSA cells exhibited cell wall damage and cell lysis. Overall results of this study suggest that CPV may be a potential anti-staphylococcal agent for MRSA.
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:Staphylococcus aureus can cause a broad spectrum of diseases that vary widely in clinical presentation and disease severity[121]. Methicillin-Resistant S. aureus (MRSA) strains first described in the 1960’s[122] were hospital acquired (HA MRSA), however in the 1990’s, community-associated MRSA strains (CA MRSA) were identified and are considered to be more virulent[16]. Therapeutics and management of MRSA focuses on novel antibacterials and vaccines targeting virulence factors. To date no clinical trials for vaccines have succeeded[123] due to the poor understanding of the pathogenic mechanisms exhibited by S.aureus.We investigated the differential gene expression of four clinical MRSA strains in vitro, belonging to HA and CA MRSA, at the stationary and exponential growth phases, using RNA-seq on the Ion torrent next generation sequencing platform. This study reveals the high diversity of virulence trait expression among MRSA strains within strains as well as between different growth phases, and also suggests potential factors other than PVL that contributes to enhanced virulence in CA MRSA
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) is a highly prioritized pathogen proposed by World Health Organization (WHO). It is listed to encourage researchers to search for effective antimicrobial agents. Previously, we isolated soil Brevibacillus sp. strain SPR19, which showed anti-MRSA activity. However, the active substances were still unknown. This study aimed to isolate and identify the anti-MRSA substances from this bacterium. The cell-free supernatant of SPR19 was subjected to salt precipitation, cation exchange, and re-versed-phase chromatography. Bioassay-guided fractionation was used to screen active sub-stances