How Vancomycin-Resistant Enterococcus Evolved in a Danish Hospital

Vancomycin-resistant Enterococcus faecium, classified by the World Health Organization as one of the highest-priority bacteria, underwent an extensive genetic study from 2012 to 2020 in Danish hospitals. Researchers from Portugal's ITQB NOVA University collected and sequenced 334 clones (ST80) from nine hospitals, identifying two major clusters and nine sub-clusters within the dominant lineage.

This sub-cluster, 1.A, comprised 72% of isolates from 2012-2015. Over the following years, the variants were distributed across all sub-clusters, suggesting increasing diversification. Genetic variation was attributed to mutations, recombination, and the gain/loss of accessory genes and plasmids. Eight recombination hotspots were detected in crucial genes, including those responsible for cell wall synthesis, phosphotransferase systems, amino-acid biosynthesis, and transporters.

The bacteria also carried a unique phage-like plasmid element that conferred resistance to multiple antibiotics through the vanA operon, ermB, aadE, and aph(3’)-IIIa. This combination could select for bacteria carrying the entire package of antimicrobial resistance. Study leader Maria Miragaia warns that reducing vancomycin use alone may not sufficiently diminish vancomycin-resistant bacteria if other linked antibiotics continue to be used.

To eliminate these resistant bacteria, the study suggests targeting strategies such as biofilm formation, surface alterations, and alternative sugar usage in the gut.