Vancomycin-Resistant <i>Enterococcus</i> Often Spreads From Hospitalized Patients Into the Local Environment and Less Often Spreads From the Environment Into Patients

BACKGROUND: Uncertainty remains about how gut-based organisms such as vancomycin-resistant Enterococcus (VRE) are spread within the local hospital environment. We hypothesized that, in the medical intensive care unit (ICU), VRE is spread predominantly patient-to-environment rather than environment-to-patient. METHODS: Medical ICU patients with sepsis and receiving broad-spectrum antibiotics were sampled via deep rectal swabs at ICU admission and on ICU days 3, 7, 14, and 30. Corresponding ICU room environmental samples were taken at the same timepoints. All samples were analyzed with 16S sequencing and selective culture, and VRE isolates were genetically characterized via whole genome sequencing (WGS). RESULTS: There were 680 samples gathered from 90 unique patients and their ICU rooms. 47/90 (52%) patients and 36/90 (40%) rooms showed VRE colonization at one or more timepoint. On 16S sequencing, Enterococcus relative abundance was enriched in room samples when the room housed a VRE positive patient (0.63% VRE(+) vs. <0.01% VRE(-), p<0.01). In a network analysis, patient and room Enterococcus were connected for VRE positive but not VRE negative patients. WGS identified 23 genetically distinct clusters of VRE. There were 3 events when distinct clusters appeared first in the patient gut and then in the room and 3 events when clusters appeared simultaneously in the gut and room; in no cases was a cluster first detected in the room. CONCLUSIONS: We detected three events when spread of genetically distinct VRE clusters from hospitalized patients into their local ICU environment but no reverse events. Effectiveness of infection prevention might be increased by gut-targeting interventions.