Project description:This study aims to determine the global gene expression in vancomycin resistant Enterococcus faecium (VRE) in response to a novel essential oil-vancomycin combination, and the individual components (vancomycin, carvacrol and cuminaldehyde) to help determine the mechanism of action of this antimicrobial formulation. This formulation increases the susceptibility of VRE to vancomycin and the array provides data on the synergistic mechanism of action. Five conditions (1. Control; 2. Carvacrol, 1.98 mM; 3. Cuminaldehyde, 4.20 mM; 4. Vancomycin, 0.031 mg/l; 5. Combination, 1.98 mM Carvacrol, 4.2 mM Cuminaldehyde, 0.031 mg/l vancomycin) all with 1% DMSO were tested in triplicate with a 60 minute exposure time before extraction.
Project description:Preliminary analysis on extracts (pellets and supernatant) of vancomycin-resistant Enterococcus faecium strains cultured in BHI media. Untargeted LC-MS/MS acquisition performed in positive ion mode.
Project description:The rise of antibiotic resistance and decline of antibiotic discovery urgently calls for novel mechanistic understanding of pharmacological and evolutionary interactions between antibiotics and multidrug resistant bacteria to revitalize existing antibiotics. The evolutionary cross-resistance to antibiotics has received intensive attention previously. Nevertheless, whether and how bacteria develop negative responses, under the selective pressure of antibiotics by inverting the evolutionary trajectory remains unclear. Here we found an instance of collateral sensitivity, in which clinical vancomycin-resistant Enterococcus faecium (VREfm) pathogens exhibit dramatic and specific susceptibility to pleuromutilin antibiotics, decreased minimal inhibitory concentrations (MICs) from 128 µg/mL to 0.03 µg/mL. The unique trade-off between vancomycin and pleuromutilins is mediated by the epistasis between the van gene cluster and msrC encoding an ABC-F protein protecting bacterial ribosomes. We validated the efficacy of pleuromutilins in vivo through reducing colonization and promoting microbiota restoration. Our findings provide an alternative approach to inverting the selective advantage and reversing the route of vancomycin resistance evolution, and to treat VREfm associated infections.
Project description:Regulatory RNAs (sRNAs) are now considered as major players in many physiological and adaptive responses in pathogenic bacteria. sRNAs have been extensively studied in Gram-negative bacteria, but less information is available in Gram-positive pathogens. There is a spread of multidrug-resistant (MDR) opportunistic organisms, grouped as “ESKAPE” pathogens, which comprise enterococci, a leading cause of hospital-acquired infections and outbreaks with emergence of MDR isolates, especially vancomycin-resistant Enterococcus faecium (VREF). Note that no information about sRNA expression is known in this major opportunistic pathogen. By transcriptomic and genomic analyses using E. faecium Aus0004 reference strain, 249 transcribed IGRs, including sRNA candidates, were detected and, using a series of cut-offs, this set was lowered down to 54 sRNAs while 7 that were predicted based on comparative sequence analysis. RNA-seq was performed with and without subinhibitory concentrations (SIC) of daptomycin, a cyclic lipopeptide antibiotic used for VREF infections. Under daptomycin SIC exposure, 260 genes (9.1% of the genome) had a significant alteration of expression including 80 upregulated genes and 180 downregulated genes. Among the repressed genes, a large proportion (55%) coded for proteins involved in carbohydrate and transport metabolism. Also, we focused on the 9 sRNAs exhibiting the highest expression, and all of them were confirmed as expressed along bacterial growth by Northern blots and qPCR. Out of these 9 sRNAs, four had significantly lower or higher expression in the presence of daptomycin SIC, and therefore responded to antibiotic exposure. Finally, we also tested the expression of these 9 sRNAs in a collection of isogenic Aus0004 mutants with increasing levels of daptomycin resistance, and we observed by qPCR that some sRNAs had a significantly modified expression in daptomycin resistance mutants. It highlights the significant implication of some of the E. faecium sRNAs in the early steps of the development of daptomycin resistance. This is the first experimental genome-wide sRNA identification in Gram-positive E. faecium, a leading cause of hospital acquired infections.
Project description:A set of small RNAs was identified in Vancomycin-resistant Enterococcus faecium, a leading cause of MDR infections. We described here the function of srn_2050, acting as a T-box riboswitch to regulate expression of downstream genes encoding the HisRS and AspRS aminoacyl-tRNA synthetases. Comparative RNAseq between Aus0004 and isogenic srn_2050 mutant identified the genes whose expression is impacted by the RNA. srn_2050 structure in its ‘off state’ was deciphered by in-line probing, containing T-box consensus sequences, a pseudoknot, a specifier loop and a terminator. Transcription binding assays between the riboswitch and either tRNAAsp or tRNAHis indicate that each deacylated tRNA interacts with the T-box. Their anticodons bind to a GACAC sequence within the specifier loop (GAC and CAC are Asp and His codons, respectively), whereas tRNATyr (UA/C-U) does not. A pioneering evaluation of E. faecium amino acid auxotrophy, with emphasis on E. faecium strain Aus0004, revealed auxotrophy for Histidine but not for Aspartic acid. Based on comparative growths and RNAseq between Aus004 and Aus004-srn2050, the riboswitch is shown essential for growth under aspartate starvation. This is the first example of a functional riboswitch in E. faecium with two overlapping codons allowing a dual tRNA-dependent regulation at transcriptional level.