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:E. faecium is inherantly resistant to cephalosporins. Resistance is lost in Class A penicillin binding protein PbfF PonA mutants, but is reversible by pencillin exposure. E. faecium Affymetrix GeneChips were used to compare E. faecium expression properties of pbfF ponA mutant cells in the absence or presence of penicillin exposure. Significant differences were observed between the expression properties of mock and penicillin treated E. faecium CV571 (pbfF ponA double mutant) cells.
Project description:Background: Bacterial small regulatory RNAs (sRNAs) have been implicated in important processes including antimicrobial stress response. However, the full extent of sRNA involvement in antimicrobial response in Staphylococcus aureus, an important pathogen, is incompletely understood. We investigated the transcriptional profiles of a linezolid-resistant, livestock-associated methicillin-resistant S. aureus (LA-MRSA) strain ST398 under conditions of linezolid stress. Methods: Cells in mid-exponential growth were subjected to low (8 µg/ml) and high (16 µg/ml) dose linezolid treatments followed by high throughput RNA sequencing. Read mapping and differential expression analysis were performed followed by detection and interrogation of various sRNA and mRNA transcripts. Results: Twenty-three putative regulatory RNA transcripts were expressed under low- and high-dose exposure conditions. Cis-acting regulatory elements, mainly targeting ribosomal biogenesis constituted the majority of transcriptional response with limited antisense and small RNA expression. Conclusions: This is the first study to investigate linezolid-responsive small RNA transcription in LA-MRSA strain ST398 and the first to query regulatory RNAs on a background of linezolid resistance. It provides preliminary insights and a basis for interrogating small RNAs in other strains in the quest to understand drug-responsive regulatory RNAs and identify potential anti-staphylococcal therapeutic candidates.
Project description:The success of Enterococcus faecium and E. faecalis evolving as multi-resistant nosocomial pathogens is associated with their ability to acquire and share adaptive traits, including mobile genetic elements (MGE) encoding antimicrobial resistance. Here, we define the mobilome in representative successful hospital associated genetic lineages, E. faecium ST17 (n=10) and ST78 (n=10), E. faecalis ST6 (n=10) and ST40 (n=10) using DNA microarray analyses. The hybridization patterns of 272 targets representing plasmid backbones (n=85), transposable elements (n=85), resistance determinants (n=67), prophages (n=29), and CRISPR-cas sequences (n=6) separated the strains according to species, and for E. faecalis also according to STs. Although plasmids belonging to the RCR-, Rep_3-, RepA_N- and Inc18-families were well represented with no significant differences in prevalence, the presence of specific replicon classes differed highly between the species; E. faecium was dominated by rep17/pRUM, rep2/pRE25, rep14/EFNP1 and rep20/pLG1 and E. faecalis by rep9/pCF10, rep2/pRE25 and rep7. Tn916-elements conferring tetracycline resistance (tetM) were found in all E. faecalis strains, but only in two E. faecium strains. A significant higher prevalence of IS256-, IS3-, ISL3-, IS200/IS605-, IS110-, IS982-, and IS4-transposases were detected in E. faecium, and of IS110-, IS982- and IS1182-transposases in E. faecalis ST6 compared to ST40. Notably, the transposases of IS981, ISEfm1 and IS1678 which have only been reported in few enterococcal isolates, were well represented in the E. faecium strains. E. faecalis ST40 strains harboured possible functional CRISPR-Cas systems, and still resistance and prophage sequences were generally well represented. Gene targets defined as the enterococcal mobilome, including plasmids, IS elements and transposons, resistance determinants, prophage sequences and CRISPR-Cas systems were highly prevalent, underlining their potential importance in the evolution of hospital associated STs. An association between axe-txe to the RepA_N-family and ω-ε-ζ to the Inc18-family, implicates the contribution of TA-systems in stable plasmid maintenance carrying virulence and resistance determinants in enterococci. The concurrent presence of defined MGE and their associated resistance markers was generally confirmed and illustrates the importance of horizontal gene transfer in the development of multidrug resistant enterococci.