Impact of stopping contact precautions on <i>vanA</i> plasmid transmission, Northern California, 2021-2023

<h4>Objective</h4>To evaluate the impact of discontinuing contact precautions for vancomycin-resistant enterococci (VRE) on strain and plasmid transmission using long-read whole-genome sequencing (WGS).<h4>Study design</h4>Before-after trial of adults with <i>Enterococcus</i> bloodstream infections pre-(Jan-Oct 2021) and post-(Oct-Dec 2021 and Jan-Oct 2023) discontinuation of contact precautions for VRE infections.<h4>Setting</h4>Quaternary referral and transplant academic medical center.<h4>Patients</h4>Hospitalized adults (≥18 yr) with <i>E. faecalis</i> or <i>E. faecium</i> bacteremia.<h4>Methods</h4>Classical epidemiology identified potential transmissions via shared unit exposure within a 14-day window. Blood culture isolates underwent long-read WGS to assess strain and <i>vanA</i> plasmid relatedness. Clonal transmission was defined as <20 single-nucleotide polymorphisms. Plasmid similarity was assessed with Mash distance.<h4>Findings</h4>Among 288 isolates from 202 patients, there was no significant difference in possible epidemiologic transmissions pre-versus postdiscontinuation (9.5% vs 8.1%; <i>P</i> = .679). Genomic analysis identified four clonal transmission events, two of which occurred postdiscontinuation. Among 70 <i>vanA</i> plasmids from 54 patients, 38 highly related plasmids formed a low-diversity cluster. The proportion of cluster plasmids was not significantly different between periods (47% vs 60%; <i>P</i> = .267). Postdiscontinuation, <i>vanA</i>-positive <i>E. faecium</i> ST117 was more prevalent (22/44 vs 53/75; <i>P</i> = .024).<h4>Conclusion</h4>Discontinuation of contact precautions for VRE was not associated with increased transmission of enterococci or <i>vanA</i> plasmids in bloodstream infections. Transmission patterns remained largely stable, though the postdiscontinuation period showed increased prevalence of the <i>dominant E. faecium</i> ST117. These findings suggest limited impact of contact precautions on VRE transmission.