Association between vancomycin-resistant Enterococcus faecium colonization and subsequent infection: a retrospective...

Area of Science:

• Microbiology
• Genomics
• Infectious Diseases

Background:

• Vancomycin-resistant Enterococcus faecium (VREfm) incidence has significantly increased in Copenhagen since 2012.
• VREfm is now endemic and polyclonal in the region, posing a growing public health concern.

Purpose of the Study:

• To determine if VREfm clinical infections originate from the same VREfm strains identified in preceding rectal screening samples.
• To investigate the genetic relatedness of VREfm isolates from screening and clinical samples.

Main Methods:

• A 30-month retrospective study analyzing VREfm pairs (screening and invasive isolates) from patients within a 60-day window.
• Whole-genome sequencing (WGS) and core-genome multilocus sequence typing (cgMLST) were used to compare isolates.
• Analysis included the presence of dominant vanA plasmids, with two novel plasmids characterized.

Main Results:

• Out of 19 VREfm pairs, 13 (68%) showed matching cgMLST types, indicating infection originated from prior colonization with the same strain.
• An additional VREfm pair (5%) had matching vanA plasmids, suggesting a potential link.
• Five pairs (26%) had non-matching cgMLST types and vanA plasmids, with longer intervals between screening and infection.

Conclusions:

• In 13 out of 19 patients, VREfm infection was preceded by colonization with genetically identical VREfm strains.
• Matching vanA plasmids were observed in some discordant pairs, suggesting potential plasmid transfer.
• The findings underscore the role of VREfm colonization in subsequent clinical infections and the utility of WGS in tracking transmission.