Abstract
BackgroundThe nosocomial pathogen Enterococcus faecium can survive for prolonged periods of time on surfaces in the absence of nutrients. This trait is thought to contribute to the ability of E. faecium to spread among patients in hospitals. There is currently a lack of data on the mechanisms that are responsible for the ability of E. faecium to survive in the absence of nutrients.ResultsWe performed a high-throughput transposon mutant library screening (Tn-seq) to identify genes that have a role in long-term survival during incubation in phosphate-buffered saline (PBS) at 20 °C. A total of 24 genes were identified by Tn-seq to contribute to survival in PBS, with functions associated with the general stress response, DNA repair, metabolism, and membrane homeostasis. The gene which was quantitatively most important for survival in PBS was usp (locus tag: EfmE745_02439), which is predicted to encode a 17.4 kDa universal stress protein. After generating a targeted deletion mutant in usp, we were able to confirm that usp significantly contributes to survival in PBS and this defect was restored by in trans complementation. The usp gene is present in 99% of a set of 1644 E. faecium genomes that collectively span the diversity of the species.ConclusionsWe postulate that usp is a key determinant for the remarkable environmental robustness of E. faecium. Further mechanistic studies into usp and other genes identified in this study may shed further light on the mechanisms by which E. faecium can survive in the absence of nutrients for prolonged periods of time.
Highlights
The nosocomial pathogen Enterococcus faecium can survive for prolonged periods of time on surfaces in the absence of nutrients
E. faecium E745 genes required for survival during starvation To investigate which genes were required for survival in phosphate-buffered saline (PBS) at 20 °C, we incubated a transposon mutant library of E745 in PBS for 7 days at 20 °C
Our Tn-seq data suggest that most genes involved in survival during nutrient deprivation are part of the core genome of E. faecium
Summary
The nosocomial pathogen Enterococcus faecium can survive for prolonged periods of time on surfaces in the absence of nutrients. This trait is thought to contribute to the ability of E. faecium to spread among patients in hospitals. Enterococcus faecium is a commensal of the human gut, but has emerged over the last few decades as an opportunistic pathogen which causes infections in hospitalized patients. While the accumulation of antibiotic resistance determinants is a major contributor to E. faecium’s emergence as an important nosocomial pathogen, other adaptations, like the ability to form biofilms [2,3,4] and interact with host extracellular matrix and serum components [5], are widespread in clinical isolates. Many nosocomial pathogens are thought to spread via environmental contamination, but E. faecium can survive 3- to 5-times longer on inanimate objects compared to other Gram-positive nosocomial pathogens, such as Enterococcus faecalis, Staphylococcus aureus, and streptococci [15,16,17]
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