Background: Enterococci are among the leading causes of hospital-acquired infections in the United States and Europe, withEnterococcus faecalisandEnterococcus faeciumbeing the two most common species isolated from enterococcal infections. In the last decade, the proportion of enterococcal infections caused byE. faeciumhas steadily increased compared to otherEnterococcusspecies. Although the underlying mechanism for the gradual replacement ofE. faecalisbyE. faeciumin the hospital environment is not yet understood, many studies using genotyping and phylogenetic analysis have shown the emergence of a globally dispersed polyclonal subcluster ofE. faeciumstrains in clinical environments. Systematic study of the molecular epidemiology and pathogenesis ofE. faeciumhas been hindered by the lack of closed, completeE. faeciumgenomes that can be used as references.Results: In this study, we report the complete genome sequence of theE. faeciumstrain TX16, also known as DO, which belongs to multilocus sequence type (ST) 18, and was the firstE. faeciumstrain ever sequenced. Whole genome comparison of the TX16 genome with 21E. faeciumdraft genomes confirmed that most clinical, outbreak, and hospital-associated (HA) strains (including STs 16, 17, 18, and 78), in addition to strains of non-hospital origin, group in the same clade (referred to as the HA clade) and are evolutionally considerably more closely related to each other by phylogenetic and gene content similarity analyses than to isolates in the community-associated (CA) clade with approximately a 3–4% average nucleotide sequence difference between the two clades at the core genome level. Our study also revealed that many genomic loci in the TX16 genome are unique to the HA clade. 380 ORFs in TX16 are HA-clade specific and antibiotic resistance genes are enriched in HA-clade strains. Mobile elements such as IS16and transposons were also found almost exclusively in HA strains, as previously reported.Conclusions: Our findings along with other studies show that HA clonal lineages harbor specific genetic elements as well as sequence differences in the core genome which may confer selection advantages over the more heterogeneous CAE. faeciumisolates. Which of these differences are important for the success of specificE. faeciumlineages in the hospital environment remain(s) to be determined.

A global transcriptional regulatory network was generated in the pathogenic bacterium Enterococcus faecalis in order to understand how this organism c

Expression of ace ( a dhesin to c ollagen of E nterococcus faecalis ), encoding a virulence factor in endocarditis and urinary tract infection models, has been shown to increase under certain conditions, such as in the presence of serum, bile salts, urine, and collagen and at 46°C. However, the mechanism of ace /Ace regulation under different conditions is still unknown. In this study, we identified a two-component regulatory system GrvRS as the main regulator of ace expression under these stress conditions. Using Northern hybridization and β-galactosidase assays of an ace promoter- lacZ fusion, we found transcription of ace to be virtually absent in a grvR deletion mutant under the conditions that increase ace expression in wild-type OG1RF and in the complemented strain. Moreover, a grvR mutant revealed decreased collagen binding and biofilm formation as well as attenuation in a murine urinary tract infection model. Here we show that GrvR plays a major role in control of ace expression and E. faecalis virulence.

Hazardous organisms may thrive on surfaces that are often exposed to human contact, including children’s library books. In this study, swab samples were taken from 42 children’s books collected from four public libraries in Texas and California. Samples were then cultivated in brain–heart infusion (BHI) medium and then in Luria broth (LB) medium containing either ampicillin or kanamycin. All 42 samples (100%) were positive for bacterial growth in normal BHI medium. Furthermore, 35 samples (83.3%) and 20 samples (47.6%) in total were positive in LB medium containing ampicillin or kanamycin, respectively. Bacterial populations were then identified in samples using an Orbitrap Fusion™ Tribrid ™ mass spectrometer, a state-of-the-art proteomic analysis tool. Identified bacterial species grown in ampicillin included Bacillus, Acinetobacter, Pseudomonas, Staphylococcus, Enterobacter, Klebsiella, Serratia, Streptococcus, Escherichia, Salmonella, and Enterococcus. In contrast, identified bacteria grown in kanamycin included Staphylococcus, Streptococcus, Enterococcus, and Bacillus. The presences of pathogenic bacteria species were also confirmed. The results of this study warrant follow up studies to assess the potential health risks of identified pathogens. This study demonstrates the utility of proteomics in identifying environmental pathogenic bacteria for specific public health risk evaluations.