Genomic Surveillance of Vancomycin-Resistant Enterococcus faecium Reveals Spread of a Linear Plasmid Conferring a Nutrient Utilization Advantage.

Healthcare-associated outbreaks of vancomycin-resistant Enterococcus faecium (VREfm) are a worldwide problem with increasing prevalence. The genomic plasticity of this hospital-adapted pathogen contributes to its efficient spread despite infection control measures. Here, we aimed to identify the genomic and phenotypic determinants of health care-associated transmission of VREfm. We assessed the VREfm transmission networks at the tertiary-care University Hospital of Zurich (USZ) between October 2014 and February 2018 and investigated microevolutionary dynamics of this pathogen. We performed whole-genome sequencing for the 69 VREfm isolates collected during this time frame and assessed the population structure and variability of the vancomycin resistance transposon. Phylogenomic analysis allowed us to reconstruct transmission networks and to unveil external or wider transmission networks undetectable by routine surveillance. Notably, it unveiled a persistent clone, sampled 31 times over a 29-month period. Exploring the evolutionary dynamics of this clone and characterizing the phenotypic consequences revealed the spread of a variant with decreased daptomycin susceptibility and the acquired ability to utilize N-acetyl-galactosamine (GalNAc), one of the primary constituents of the human gut mucins. This nutrient utilization advantage was conferred by a novel plasmid, termed pELF_USZ, which exhibited a linear topology. This plasmid, which was harbored by two distinct clones, was transferable by conjugation. Overall, this work highlights the potential of combining epidemiological, functional genomic, and evolutionary perspectives to unveil adaptation strategies of VREfm. IMPORTANCE Sequencing microbial pathogens causing outbreaks has become a common practice to characterize transmission networks. In addition to the signal provided by vertical evolution, bacterial genomes harbor mobile genetic elements shared horizontally between clones. While macroevolutionary studies have revealed an important role of plasmids and genes encoding carbohydrate utilization systems in the adaptation of Enterococcus faecium to the hospital environment, mechanisms of dissemination and the specific function of many of these genetic determinants remain to be elucidated. Here, we characterize a plasmid providing a nutrient utilization advantage and show evidence for its clonal and horizontal spread at a local scale. Further studies integrating epidemiological, functional genomics, and evolutionary perspectives will be critical to identify changes shaping the success of this pathogen.

Possible Prosthetic Valve Endocarditis by Pandoraea pnomenusa and Specific Virulence Mechanisms.

Bacteremia by Pandoraea spp. has rarely been described before. We report the first case of a P. pnomenusa possible prosthetic valve endocarditis, according to the modified Duke criteria, in a 37-year old male injecting drug user suffering from recurrent endocarditis. Furthermore, we demonstrate biofilm formation by the P. pnomenusa isolates of this patient and investigate antibiotic resistance.

Determinants for voluntary participation in staff screening during an methicillin-resistant Staphylococcus aureus (MRSA) outbreak on a neonatal ward.

We investigated healthcare worker (HCW) behavior with regard to a voluntary methicillin-resistant Staphylococcus aureus (MRSA) staff screening during a MRSA outbreak in a neonatal ward. Avoiding MRSA transmission from HCWs to patients was the most important reason for participation. Inconvenient screening time was the most frequently cited reason for nonparticipation.

ROR1 is expressed on hematogones (non-neoplastic human B-lymphocyte precursors) and a minority of precursor-B acute lymphoblastic leukemia.

ROR1 is a receptor tyrosine kinase expressed during embryogenesis, on chronic lymphocytic leukemia (CLL) and in other malignancies. Hematogones (non-neoplastic B-lymphocyte precursors) express surface ROR1 at an intermediate stage of maturation that lacks CD34 or TdT. The neoplastic counterpart to hematogones is precursor-B acute lymphoblastic leukemia (B-ALL), but less than 10% of B-ALL express surface ROR1, and these ROR1+ B-ALL cases have an unusually high frequency of lacking CD34 and/or having t(1;19), a chromosomal translocation that defines a specific subtype of B-ALL.