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.
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-1M-NM-2 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-M-NM-1, 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 translation inhibitor Linezolid is an important antibiotic of last resort against multiresistant gram-positive pathogens including MRSA. Linezolid is reported to specifically inhibit extracellular virulence factors, but the molecular cause is unknown. To elucidate the physiological response of S. aureus to Linezolid in general and the possible inhibition of virulence factors specifically we performed a holistic study. We added Linezolid to logarithmically growing S. aureus cells and analyzed the Linezolid stress response with transcriptomics, quantitative proteomics and microscopy experiments. As previously observed in studies on other translation inhibitors S. aureus is adapting its protein biosynthesis machinery to the reduced translation efficiency, for example the synthesis of ribosomal proteins is induced. But we also observed unexpected results like a general decline in the amount of extracellular and membrane proteins. In addition cell shape and size changed after Linezolid stress and cell division was diminished. Finally, the chromosome condensed after LZD stress and lost contact to the membrane.
Project description:The translation inhibitor Linezolid is an important antibiotic of last resort against multiresistant gram-positive pathogens including MRSA. Linezolid is reported to specifically inhibit extracellular virulence factors, but the molecular cause is unknown. To elucidate the physiological response of S. aureus to Linezolid in general and the possible inhibition of virulence factors specifically we performed a holistic study. We added Linezolid to logarithmically growing S. aureus cells and analyzed the Linezolid stress response with transcriptomics, quantitative proteomics and microscopy experiments. As previously observed in studies on other translation inhibitors S. aureus is adapting its protein biosynthesis machinery to the reduced translation efficiency, for example the synthesis of ribosomal proteins is induced. But we also observed unexpected results like a general decline in the amount of extracellular and membrane proteins. In addition cell shape and size changed after Linezolid stress and cell division was diminished. Finally, the chromosome condensed after LZD stress and lost contact to the membrane. sample versus pool design (pool = mixture of equal amounts of all RNA samples analyzed), all RNA samples were isolated as biological triplicates
Project description:Coordinated protein-coding sequence transcriptional responses of Staphylococcus aureus to antimicrobial exposure are well described but little is known of the role of bacterial non-coding, small RNAs (sRNAs) in these responses. Here we used RNAseq to investigate the sRNA response of the epidemic multiresistant hospital ST239 S. Aureus strain JKD6009 and its vancomycin-intermediate clinical derivative, JKD6008, after exposure to four antibiotics representing the major classes of antimicrobials used to treat methicillin-resistant S. Aureus infections. These agents included vancomycin, linezolid, ceftobiprole, and tigecycline. We identified 410 potential sRNAs (sRNAs) and then compared global sRNA and mRNA expression profiles at 2 and 6 hours, without antibiotic exposure, and after exposure to 0.5 x MIC for each antibiotic, for both JKD6009 (VSSA), and JKD6008 (VISA). Two strains were used (JKD6009, vancomycin-susceptible S. Aureus; JKD6008, in vivo derived vancomycin-intermediate S. Aureus). The complete JKD6008 genome seqeuce was used as the reference. Two time points, 2 hours and 6 hours after culture in Mueller Hinton broth. Strains were exposed to no antibiotic, or 0.5 x MIC for 10 mins for the following antibiotics; vancomycin, linezolid, ceftobiprole, tigecycline. RNA isolation procedures enriched for mRNA or sRNA. The 40 cDNA libraries were sequenced using a whole flowcell (8 lanes) in an Illumina genome analyzer GAII for 36 cycles. Data was analyzed using the BioConductor package limma, and by applying non-negative matrix factorization to determine the impact of antibiotic exposure on the sRNA and mRNA transcriptional profiles.
Project description:The study aims to identify genes associated with Linezolid resistance. Linezolid resistant strains were compared to a Linezolid sensitive reference strain in the presence of linezolid and absence of linezolid (mock).
Project description:The translation inhibitor Linezolid is an important antibiotic of last resort against multiresistant gram-positive pathogens including MRSA. Linezolid is reported to specifically inhibit extracellular virulence factors, but the molecular cause is unknown. To elucidate the physiological response of S. aureus to Linezolid in general and the possible inhibition of virulence factors specifically we performed a holistic study. We added Linezolid to logarithmically growing S. aureus cells and analysed the Linezolid stress response with transcriptomics, quantitative proteomics and microscopy experiments.