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

Objectives: We aimed to characterize the vanE cluster and its genetic support in the first Norwegian vanE -type isolates and assess genetic relatedness to other vanE isolates. Methods: Two vanE -type vancomycin resistant Enterococcus faecalis ( vanE -VRE fs ) isolates (E1 and E2) recovered from the same patient 30 months apart were examined for antimicrobial susceptibility, genome sequence, vancomycin resistance induction, vanE transferability, genome mutation rate, and phylogenetic relationship to E. faecalis closed genomes and two vanE -VR Efs from North America. Results: The ST34 E1 and E2 strains expressed low-level vancomycin resistance and susceptibility to teicoplanin. Their vanE gene clusters were part of a non-transferable Tn 6202 . The histidine kinase part of vanSE was expressed although a premature stop codon (E1) and insertion of a transposase (E2) truncated their vanSE gene. The vancomycin resistance phenotype in E1 was inducible while constitutive in E2. E1 showed a 125-fold higher mutation rate than E2. Variant calling showed 60 variants but nearly identical chromosomal gene content and synteny between the isolates. Their genomes also showed high similarity to another ST34 vanE -VRE fs from Canada. Conclusion: In-depth genomic analyses of the first two vanE -VRE fs found in Europe identified a single chromosomal insertion site of two variants of vanE -conferring Tn 6202 . Single nucleotide polymorphism (SNP) and core genome multilocus sequence type (cgMLST) analyses show the genomes are different. This can be explained by the high mutation rate of E1 and acquisition of different mobile genetic elements; thus, we believe the two isolates from the same patient are genetically related. Genome similarities also suggest relatedness between the Canadian and Norwegian vanE -VRE fs . (c) 2024 The Authors. Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )