Substantial Decrease in Vancomycin-Resistant Enterococcus faecium Outbreak Duration and Number of Patients During the Danish COVID-19 Lockdown: A Prospective Observational Study

Vancomycin-resistant Enterococcus faecium (VREfm) is a globally significant nosocomial pathogen with a rapidly increasing prevalence. The objectives were to investigate VREfm outbreak duration and study the additional impact that infection control bundle strategies (ICBSs) set up to curb coronavirus disease 2019 (COVID-19) spreading had on VREfm outbreaks. Outbreak data set were collected prospectively from April 2, 2014 to August 13, 2020 at Copenhagen University Hospital Bispebjerg, Denmark. All VREfm samples had polymerase chain reaction performed for vanA/vanB genes before whole genome sequencing using the Illumina MiSeq platform. The relatedness of isolates was studied by core genome multilocus sequence typing (cgMLST) using Ridom SeqSphere. Eighty-one outbreaks had a median outbreak duration of 32.5 days (range 5-204 days) and 1,161 VREfm isolates were sequenced. The same cgMLST cluster types reappeared after outbreaks were terminated. When comparing the first 5 months of the COVID-19 pandemic with the corresponding period in 2019, we found a 10-fold decrease in VREfm outbreak patients and median outbreak duration decreased from 56 to 7 days (88%). Several COVID-19 ICBSs were implemented from March 13 through summer 2020. VREfm outbreaks lasted up to 204 days, but our findings suggest that outbreaks might last longer since the same cgMLST persisted in the same wards for years implying an endemic situation with recurrent outbreaks caused by hospital reservoirs or readmittance of unknown VREfm carriers. The sharp decline in VREfm outbreaks during the COVID-19 pandemic was most likely due to the ICBSs, resulting in a decrease in VREfm transmission.