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:Several methicillin resistance (SCCmec) clusters characteristic of hospital-associated methicillin-resistant Staphylococcus aureus (MRSA) strains harbor the psm-mec locus. In addition to encoding the cytolysin, phenol-soluble modulin (PSM) mec, this locus has been attributed gene regulatory functions. Here we employed genome-wide transcriptional profiling to define the regulatory function of the psm-mec locus. The immune evasion factor protein A emerged as the primary conserved and strongly regulated target of psm-mec, an effect we show is mediated by the psm-mec RNA. Furthermore, the psm-mec locus exerted regulatory effects that were more moderate in extent and possibly mediated by the PSM-mec peptide. For example, expression of PSM-mec limited expression of mecA, thereby decreasing methicillin resistance. Our study shows that the psm-mec locus has a rare dual regulatory RNA and encoded cytolysin function, both with the potential to enhance MRSA virulence. Furthermore, our findings reveal a specific mechanism underscoring the recently emerging concept that S. aureus strains balance pronounced virulence and high expression of antibiotic resistance.
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:Whole-genome analysis by 62-strain microarray showed variation in resistance and virulence genes on mobile genetic elements (MGEs) between 40 isolates of methicillin-resistant Staphylococcus aureus (MRSA) strain CC22-SCCmecIV but also showed (i) detection of two previously unrecognized MRSA transmission events and (ii) that 7/8 patients were infected with a variant of their own colonizing isolate. [Data is also available from http://bugs.sgul.ac.uk/E-BUGS-128]
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 is one of the major causative agents associated to infections with a high morbidity and mortality in hospitals worldwide. In previous studies, we reported that lignan 3'-demethoxy-6-O-demethylisoguaiacin isolated and characterized from Larrea tridentata showed the best activity towards methicillin-resistant S. aureus. Understanding of mechanism of action of drugs allows design drugs in a better way. Therefore, we employed microarray to obtain gene expression profile of methicillin-resistant S. aureus after exposure to 3'-demethoxy-6-O-demethylisoguaiacin. The results showed that lignan had an effect on cell membrane affecting proteins of the ATP-binding cassette (ABC) transport system causing bacteria death. This study consisted of comparison of isolated RNA of MRSA not treated and MRSA treated with lignan 3'-demethoxy-6-O-demethylisoguaiacin. Both RNAs samples were differentially dyed with Cy3 and Cy5 during cDNA synthesis and hybridized on DNA chip. Afterwards, the chip was scanned in a GenePix 4000B scanner. The resulting gene expression profile was analyzed in databases for functional annotations to find a potential mechanism of the lignan in MRSA.
Project description:Methicillin-resistant Staphylococcus aureus (MRSA) strains are important human pathogens and a significant health hazard for hospitals and the food industry. They are resistant to β-lactam antibiotics including methicillin and extremely difficult to treat. In this study, we show that the Staphylococcus aureus COL (MRSA) strain, with a known complete genome, can easily survive and grow under acidic and alkaline conditions (pH 5 and pH9, respectively), both planktonically and as a biofilm. Α microarray-based analysis of both planktonic and biofilm cells was performed under acidic and alkaline conditions showing that several genes are up- or down-regulated under different environmental conditions and growth modes. These genes were coding for transcription regulators, ion transporters, cell wall biosynthetic enzymes, autolytic enzymes, adhesion proteins and antibiotic resistance factors, most of which are associated with biofilm formation. These results will facilitate a better understanding of the physiological adjustments occurring in biofilm-associated S. aureus COL cells growing in acidic or alkaline environments, which will enable the development of new efficient treatment or disinfection strategies. We used microarrays to detail the global programme of gene expression underlying growth of S. aureus COL growing under acidic and alkaline conditions in biofilm or planktonic mode and identified distinct classes of up-regulated genes during this process.
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.