Effect of Hamamelitannin, vancomycin and combination treatment of Hamamelitannin and vancomycin on gene expression in S. aureus Mu50 biofilms
ABSTRACT: Novel anti-infective agents targeting Staphylococcus aureus and capable of increasing S. aureus susceptibility towards antibiotics are needed. One alternative approach is targeting the bacterial quorum sensing (QS) system. QS is a process by which bacteria produce and detect signal molecules and thereby coordinate their behaviour, virulence and biofilm formation in a cell-density-dependent manner. Hamamelitannin (HAM) was previously suggested to target the S. aureus QS system, thereby increasing the susceptibility of S. aureus biofilms towards vancomycin. However, mechanistic insights are still lacking. For this reason, we evaluated the effect of Hamamelitannin, vancomycin and combination treatment of Hamamelitannin and vancomycin on gene expression in S. aureus Mu50 biofilms.
Project description:To determine if significant genomic changes are associated with the development of vancomycin intermediate Staphylococcus aureus, genomic DNA microarrays were performed to compare the initial vancomycin susceptible Staphylococcus aureus (VSSA) and a related vancomycin intermediate Staphylococcus aureus (VISA) isolate from five unique patients (five isolate pairs). Keywords: comparative genomic hybridization Overall design: A single 2-channel array was performed for each isolate pair using genomic DNA. Raw data was compiled using IMAGENE. Normalisation and statistical analysis was undertaken using BASE. Statistics were performed using the Wilcoxon signed ranked test.
Project description:The precise mechanism and effects of antibiotics in host gene expression and immunomodulation in MRSA infection is unknown. Using a well characterized Methicillin Resistant Staphylococcus aureus (MRSA) isolate USA300 in a murine model of infection, we determined that linezolid and vancomycin induced differential production of bacterial toxins and host cytokines, differences in host gene expression, and differences in immunomodulators during MRSA bloodstream infection. A total of 35 A/J mice, categorized into seven groups (no infection; no infection with linezolid; no infection with vancomycin; 2 hour post-infection (hpi) S. aureus; 24 hpi S. aureus; 24 hpi S. aureus with linezolid; and 24 hpi S. aureus with vancomycin), were used in this study. Mice were injected with USA300 (6 x 106 CFU/g via i.p. route), then intravenously treated with linezolid (25 mg/kg) or vancomycin (25 mg/kg) at 2 hpi. Control and S. aureus infected mice were euthanized at each time point (2 h or 24h) following injection. Whole blood RNA was used for microarray; three cytokines and two S. aureus toxins [PantonValentine Leukocidin (PVL) and alpha hemolysin] were quantified in mouse serum by ELISA. S. aureus CFUs were significantly reduced in blood and kidney after linezolid or vancomycin treatment in S. aureus-infected mice. In vivo IL-1β in mouse serum was significantly reduced in both linezolid (p=0.001) and vancomycin (p=0.006) treated mice compared to untreated ones. IL-6 was significantly reduced only in linezolid treated (p<0.001) but not in vancomycin treated mice. However, another proinflammatory cytokine, TNF-α, did not exhibit altered levels in either linezolid or vancomycin treated mice (p=0.3 and p=0.51 respectively). In vivo level of bacterial toxin, Panton-Valentine leukocidin, in mouse serum was significantly reduced only in linezolid treated mice (p=0.02) but not in vancomycin treated mice. There was no significant effect of either treatment in in vivo level of alpha hemolysin production. Unsupervised hierarchical clustering using the gene expression data from 35 microarrays revealed distinct clustering based on infection status and treatment group. Study of the antibiotic-specific difference in gene expression identified the number of genes uniquely expressed in response to S. aureus infection, infection with linezolid treatment, and infection with vancomycin treatment. Pathway associations study for the differentially expressed genes in each comparison group (Control vs. 24 h S. aureus infection, 24 h S. aureus infection vs. 24 h S. aureus linezolid, and 24 h S. aureus infection vs. 24 h S. aureus vancomycin) in mice using Kyoto Encyclopedia of Genes and Genomes (KEGG) identified toll-like receptor signaling pathway to be common to every comparison groups studied. Glycerolipid metabolism pathway was uniquely associated only with linezolid treatment comparison group. The findings of this study provide the evidence that protein synthesis inhibitor like linezolid does a better job in treating MRSA sepsis compared to cell wall acting antibiotics like vancomycin. To identify differences in host gene expression in a murine sepsis model treated with a) linezolid and b) vancomycin, we used whole blood gene expression (RNA) signatures from A/J inbred mice infected with USA 300 MRSA to evaluate differences in host gene expression among mice treated with linezolid and vancomycin. We used 5 RNA samples from MRSA-infected, linezolid- or vancomycin-treated mice. A total of 7 experimental groups have been employed: 1) Uninfected control group: (negative controls). 2) Uninfected, linezolid-treated group: Uninfected, linezolid-treated mice. 3) Uninfected vancomycin-treated group: Uninfected, vancomycin-treated mice. 4) Infected control group (positive control 2 h) MRSA-infected, untreated mice. 5) Infected control group (positive control 24 h): MRSA-infected, untreated mice. 6) Infected linezolid group: MRSA-infected, linezolid-treated mice. 7) Infected vancomycin group: MRSA-infected, vancomycin-treated mice.
Project description:The glycopeptide antibiotic vancomycin (VCM) represents one of the last lines of defense against methicillin-resistant Staphylococcus aureus infections. However, vancomycin is nephrotoxic, but the mechanism of toxicity is still unclear. The goal of this study was twofold: (1) gain insights into the molecular mechanisms of vancomycin nephrotoxicity at the genomic level and (2) evaluate potential biomarkers (gene expression profiles) of vancomycin-induced kidney injury Keywords: Dose response Overall design: Groups of 6 female BALB/c mice were treated with 7 daily iv or ip doses of vancomycin (50, 200, and 400 mg/kg) or saline, and sacrificed on Day 8
Project description:S. aureus biofilms are associated with the organism's ability to cause disease. Biofilm associated bacteria must cope with the host's innate immune system. We used commercially available Affymetrix S. aureus GeneChips to compare the gene expression properties of 4 and 6 day established biofilms following short (1 hr)- and long (24 hr)- term exposure to macrophages and neutrophils. S. aureus strain USA300 LAC biofilms where formed for 4 or 6 days. Established biofilms were then exposed to macrophages for 1 or 24 hr. Alternatively, biofilms were exposed to neutrophils for 1 or 4 hr. Total bacterial RNA was isolated and subjected to GeneChip hybridization and analysis. We sought to determine the regulatory effects of Macrophages and Neutrophils on established S. aureus biofilms.
Project description:Investigation of baseline transcription activity of two different clinical isolates of Staphylococcus aureus with two different susceptibility levels to the antibiotics Vancomycin and Daptomycin. Two different strains of Staphylococcus aureus, one that is fully Vancomycin and Daptomycin Sensitive and one with decreased Vancomycin and Daptomycin Sensitivity - grown to mid-log phase in rich broth.
Project description:Complete reconstitution of the vancomycin-intermediate Staphylococcus aureus (VISA) phenotype of Mu50 was achieved by sequentially introducing mutations into five genes of a vancomycin-susceptible S. aureus (VSSA) strain ∆IP. Introduction of mutation Ser329Leu into vraS encoding the sensor histidine kinase of vraSR two-component regulatory (TCR) system and another mutation Glu146Lys into msrR, encoding putative methionine sulfoxide reductase regulator, raised vancomycin resistance to the level of heterogeneously vancomycin-intermediate S. aureus (hVISA) strain Mu3. Introduction of two more mutations, graR (Asn197Ser) of graSR TCR system and rpoB(His481Tyr) encoding ß subunit of RNA polymerase, converted the hVISA strain into a VISA strain having the level of vancomycin resistance of Mu50. Surprisingly, however, the constructed quadruple mutant strain did not have thickened cell wall, a cardinal feature of VISA phenotype. Subsequent study showed that cell-wall thickening was an inducible phenotype with the mutant strain as opposed to that of Mu50, which is a constitutive one. Finally, introduction of mutation Ala297Val into the orf SAV2309 of the mutant strain converted the inducible cell-wall thickening into a constitutive one. SAV2309 encodes a putative formate dehydrogenase (designated Fdh2). Though not a transcription regulator, the mutation of the fdh2 caused a significant change in transcriptome. Thus, all of the five mutated genes required for VISA phenotype acquisition were directly or indirectly involved in the regulation of cell physiology. VISA seemed to be achieved through multiple genetic events accompanying drastic changes in cell physiology. Overall design: We investigated the expression of genes involved in vancomycin resistance in Staphylococcus aureus, using a 60mer oligo array.
Project description:The glycopeptide antibiotic vancomycin (VCM) represents one of the last lines of defense against methicillin-resistant Staphylococcus aureus infections. However, vancomycin is nephrotoxic, but the mechanism of toxicity is still unclear. The goal of this study was twofold: (1) gain insights into the molecular mechanisms of vancomycin nephrotoxicity at the genomic level and (2) evaluate potential biomarkers (gene expression profiles) of vancomycin-induced kidney injury Experiment Overall Design: Groups of 6 female BALB/c mice were treated with 7 daily iv or ip doses of vancomycin (50, 200, and 400 mg/kg) or saline, and sacrificed on Day 8
Project description:Understanding novel mechanism bacteria ustilize in the clinics to become resistant to antibiotics is critical. The study aims to identify genes associated with Vancomycin resistance. Clinical isolates from a single patient with increasing resistance to vancomycin were grown in the presence and absence of vancomycin.Staphylococcus aureus strain 2275 is the reference for this series. Overall design: S. aureus isolates from a single patient were grown in the presence and absence of vancomycin over a 2 hour time course. RNA samples were extracted at 30, 60 90 and 120 minutes post exposure to antibiotic. Samples were hybridized on aminosilane coated slides with 70-mer oligos comparing mock treated and treated cells to the first strain isolated in the lineage. Differnetial gene expression patterns were determined.
Project description:Staphylococcus aureus is a notorious bacterial pathogen that causes a broad range of human diseases, and isolates that are resistant to several antibiotic classes including last resort antibiotics like vancomycin and daptomycin complicate the situation. We characterized S. aureus VC40, a strain that shows full resistance to vancomycin (MIC of 64 µg/ml) and daptomycin (MIC of 4 µg/ml) as well as a decreased susceptibility to further cell wall active agents. Genome sequencing revealed mutations in genes encoding the histidine kinases WalK and VraS that control cell envelope related processes and gene expression profiling indicated the induction of the respective regulons in strain VC40. Reconstitution of the mutations in walK or vraS into the susceptible S. aureus NCTC 8325 background resulted in a considerably increased resistance to vancomycin and daptomycin with MICs surpassing the clinical breakpoints for these antibiotics, thereby generating vancomycin-intermediate S. aureus (VISA) strains. As observed for S. aureus VC40, the walKwalk and vraS mutations also led to an increased expression of the respective regulons in the NCTC 8325 background. Phenotypic studies showed that S. aureus VC40 as well as the walKwalk and vraS mutants of strain NCTC 8325 were characterized by a significantly thickened cell wall, a decreased growth rate, a reduced autolytic activity and an increased resistance to lysostaphin-induced lysis. These results demonstrate that the WalK and VraS histidine kinases act as major switches which allow S. aureus to rapidly develop vancomycin resistance up to the VISA level via mutation of one single gene locus and concomitantly contribute to cross-resistance to other antibiotics including the last resort antibiotic daptomycin. Microarray was used to evaluate alteration in the transcriptome of mutS mutant and compared to the parental strain VC40
Project description:Understanding novel mechanism bacteria ustilize in the clinics to become resistant to antibiotics is critical. The study aims to identify genes associated with Vancomycin resistance. Clinical isolates from a single patient with increasing resistance to vancomycin were grown in the presence and absence of vancomycin.Staphylococcus aureus strain 2275 is the reference for this series. S. aureus isolates from a single patient were grown in the presence and absence of vancomycin over a 2 hour time course. RNA samples were extracted at 30, 60 90 and 120 minutes post exposure to antibiotic. Samples were hybridized on aminosilane coated slides with 70-mer oligos comparing mock treated and treated cells to the first strain isolated in the lineage. Differnetial gene expression patterns were determined.