To sequence a vancomycin-resistant Enterococcus faecium and analyze the vanM gene cluster carried on its plasmid as well as the genes conferring advantage in nutrient utilization.

The broth microdilution method was used to perform drug susceptibility tests on strain 15P371 and its transconjugant J15P371. Subsequently, whole-genome sequencing was conducted using Nanopore technology for both strains, followed by analysis of the resistant plasmid sequences. Bacterial growth experiments were carried out to verify the advantage in intestinal nutrient utilization.

Strain 15P371 is a vancomycin-resistant strain carrying 6 copies of the vanM gene cluster. Its transconjugant J15P371 can tolerate a higher concentration of vancomycin but only harbors 3 copies of the vanM gene cluster. Genes conferring advantage in intestinal N-acetylgalactosamine utilization are present on the resistant plasmid.

In vanM-type vancomycin-resistant strain, the copy number of resistance genes is variable during conjugative transfer. The plasmid carrying genes with advantage in N-acetylgalactosamine utilization confer growth advantage to the host bacteria.