Demonstrating shedding of vancomycin-resistant Enterococcus faecium (VREfm) into the hospital environment by colonized patients based on typing by whole genome sequencing

Introduction: Colonized or infected patients and contaminated hospital contact surfaces serve as reservoir of nosocomial pathogens and risk for transmission.

Goals: Contamination of patient contact surfaces in hospital environment was examined regarding the persistence and transmission of vancomycin-resistant Enterococcus faecium (VREfm).

Materials & Methods: Environmental samplings by swabbing the patient contact sites were performed on 20 hospital wards in 56 isolation rooms occupied with VREfm colonized or infected patients detected on admission. Some samplings were repeated over multiple follow-ups during a patient's stay in the room and after discharge to assess VREfm persistence on hospital fomites. Collected environmental samples were evaluated for contamination with E. faecium. VREfm isolates recovered from environmental sites and strains derived from positive surveillance cultures of inpatients were examined for molecular epidemiological associations by clonal relatedness using whole genome sequencing (WGS) and core-genome multi-locus sequence typing.

Results: Of 550 surface samples, 122 sites (21.8%) were contaminated with E. faecium, 8.2% with VREfm and 12.3% with vancomycin-susceptible E. faecium (VSEfm). The VRE and VSEfm isolates were recovered in 36 (64.3%) isolation rooms occupied with VREfm or VSE colonized patients. In total, 57 environmental isolates and 45 VREfm strains derived from patient clinical or screening cultures were subjected to WGS. Molecular WGS-based typing revealed 7 genotypically distinct clusters of VREfm of diverse sequence type (ST117, ST80, ST2528, ST1299) with vanA, vanB genotypes including indistinguishable and genetically closely related (≤3 alleles differing) patient and environmental isolates.

Summary: WGS-based typing identified indistinguishable environmental VREfm contaminants on hospital fomites and strains from inpatients with colonization suggesting VREfm shedding from patient to environment as potential reservoirs of nosocomial pathogens and vectors for cross-transmission in hospitals highlighting the importance of disinfection, surveillance cultures, contact precautions and isolation of VREfm-positive patients.