Abstract
Enterococcus faecium is an important health care-associated pathogen that is difficult to treat due to the high level of antibiotic resistance of clinical isolates. The identification of new potential therapeutic targets or vaccination strategies is therefore urgently needed. In this regard, we carried out a transcriptomic analysis of the E. faecium vancomycin-resistant strain AUS0004, comparing the gene expression of bacteria grown under laboratory conditions and bacteria isolated from an infection site. This analysis highlighted more than 360 genes potentially induced under infection conditions. Owing to their expression profiles, four LysM domain-containing proteins were characterized in more detail. The EFAU004_01059, 1150 and 494 proteins are highly homologous, whereas EFAU004_01209 has a unique domain-architecture and sequence. The analysis of corresponding mutants showed that all LysM proteins played relevant roles in the infection process of E. faecium in mice. The EFAU004_01209 mutant also displayed profound morphological modifications, suggesting it has a role in cell wall synthesis or cell division. Furthermore, the adhesion to kidney cells and growth of the mutant was affected in human urine. All these phenotypes and the surface exposure of EFAU004_01209 identify this protein as an interesting new drug target in E. faecium.
Highlights
Enterococci are Gram-positive bacteria that colonize several ecological niches, including the guts of mammals and numerous other animals[1]
To gain an understanding of the adaptation of E. faecium to the host environment and identify cell wall associated proteins expressed during infection, E. faecium strain Aus000414 was-inoculated into the mouse peritoneum, and bacteria were recovered 24 hours post-infection
Total RNA from bacteria grown in vivo and in vitro was extracted, and RNA sequencing (RNAseq) was performed to analyze the transcriptional activity under these different conditions
Summary
Enterococci are Gram-positive bacteria that colonize several ecological niches, including the guts of mammals and numerous other animals[1] These bacteria have emerged as important nosocomial pathogens due to their multiple antibiotic resistances[2]. Well expressed and abundant proteins, located on the surface of bacteria during the infection process, could be potential targets for new drugs or vaccines[11,12,13] To identify these surface proteins in E. faecium, we conducted a comprehensive RNA sequencing (RNAseq) transcriptome analysis on the E. faecium vancomycin resistant strain Aus0004 isolated from a bloodstream infection[14]. Prokaryotic LysM modules bind non covalently to the N-acetylglucosamine moieties of PG, the main component of the bacterial cell wall[18] This domain can be present in one or multiple copies and be located at the N- or C-terminal parts of the corresponding proteins[18]. On the basis of the induction of the corresponding genes, we decided to study the physiologic in vitro and in vivo roles of the LysM domain-containing proteins in E. faecium AUS0004
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