The first vanE-type vancomycin resistant Enterococcus faecalis isolates in Norway - phenotypic and molecular...

Area of Science:

• Microbiology
• Genomics
• Antimicrobial Resistance

Background:

• Vancomycin-resistant Enterococcus faecalis (VREfs) poses a significant global health threat.
• The vanE gene cluster is a less common mechanism of vancomycin resistance in Enterococcus species.

Purpose of the Study:

• To characterize the vanE gene cluster in the first Norwegian vanE-VREfs isolates.
• To investigate the genetic support and transferability of the vanE cluster.
• To assess the genetic relatedness of these isolates to other vanE-VREfs.

Main Methods:

• Antimicrobial susceptibility testing.
• Whole-genome sequencing.
• Analysis of vanE gene cluster and surrounding genetic elements.
• Comparative genomic analysis including SNP and cgMLST.

Main Results:

• Two Norwegian ST34 vanE-VREfs isolates (E1 and E2) showed low-level vancomycin resistance and teicoplanin susceptibility.
• The vanE gene cluster was located within a non-transferable Tn6202 element.
• Truncations in the vanS_E gene were observed, leading to inducible (E1) and constitutive (E2) vancomycin resistance.
• Isolate E1 exhibited a significantly higher mutation rate than E2.
• Genomic data indicated high similarity to a Canadian ST34 vanE-VREfs isolate.

Conclusions:

• The first European vanE-VREfs isolates harbor a chromosomal Tn6202 insertion.
• Despite genomic differences attributed to high mutation rates and mobile element acquisition, the two Norwegian isolates are genetically related.
• Genomic similarities suggest a shared ancestry or epidemiological link between Norwegian and North American vanE-VREfs strains.