Year-end Sale % OFF 
Abstract
BackgroundThe Gram-positive bacterium Enterococcus faecium is a commensal of the human gastrointestinal tract and a frequent cause of bloodstream infections in hospitalized patients. The mechanisms by which E. faecium can survive and grow in blood during an infection have not yet been characterized. Here, we identify genes that contribute to growth of E. faecium in human serum through transcriptome profiling (RNA-seq) and a high-throughput transposon mutant library sequencing approach (Tn-seq).ResultsWe first sequenced the genome of E. faecium E745, a vancomycin-resistant clinical isolate, using a combination of short- and long read sequencing, revealing a 2,765,010 nt chromosome and 6 plasmids, with sizes ranging between 9.3 kbp and 223.7 kbp. We then compared the transcriptome of E. faecium E745 during exponential growth in rich medium and in human serum by RNA-seq. This analysis revealed that 27.8% of genes on the E. faecium E745 genome were differentially expressed in these two conditions. A gene cluster with a role in purine biosynthesis was among the most upregulated genes in E. faecium E745 upon growth in serum. The E. faecium E745 transposon mutant library was then used to identify genes that were specifically required for growth of E. faecium in serum. Genes involved in de novo nucleotide biosynthesis (including pyrK_2, pyrF, purD, purH) and a gene encoding a phosphotransferase system subunit (manY_2) were thus identified to be contributing to E. faecium growth in human serum. Transposon mutants in pyrK_2, pyrF, purD, purH and manY_2 were isolated from the library and their impaired growth in human serum was confirmed. In addition, the pyrK_2 and manY_2 mutants were tested for their virulence in an intravenous zebrafish infection model and exhibited significantly attenuated virulence compared to E. faecium E745.ConclusionsGenes involved in carbohydrate metabolism and nucleotide biosynthesis of E. faecium are essential for growth in human serum and contribute to the pathogenesis of this organism. These genes may serve as targets for the development of novel anti-infectives for the treatment of E. faecium bloodstream infections.
Highlights
The Gram-positive bacterium Enterococcus faecium is a commensal of the human gastrointestinal tract and a frequent cause of bloodstream infections in hospitalized patients
To perform highthroughput functional genomics in ampicillin-resistant, vancomycin-susceptible clinical E. faecium strains, we previously developed a microarray-based transposon mutagenesis screening method which was used to identify genes involved in the development of endocarditis [7], resistance to ampicillin [21], bile [22] and disinfectants [23]
E. faecium E745 was isolated from a rectal swab of a hospitalized patient as part of routine surveillance during an outbreak of VRE in the nephrology ward of a Dutch hospital in 2000 [27, 28]
Summary
The Gram-positive bacterium Enterococcus faecium is a commensal of the human gastrointestinal tract and a frequent cause of bloodstream infections in hospitalized patients. Enterococci are commensals of the gastrointestinal tract of humans and animals, but some enterococcal species, E. faecium and E. faecalis, are common causes of hospital-acquired infections in immunocompromised patients [1]. Clade A-1 E. faecium strains are rarely found in healthy individuals but can colonize the gut of immunosuppressed, hospitalized patients to high-levels. These strains can cause infections by direct translocation from the gut into the bloodstream [10,11,12]. To thrive in the bloodstream, an opportunistic pathogen has to evade host immune mechanisms and to adjust its metabolism to an environment that is relatively poor in nutrients [18]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
