Novel vancomycin resistance gene cluster in Enterococcus faecium ST1486, Belgium, June 2021

Area of Science:

• Microbiology
• Genetics
• Antimicrobial Resistance

Background:

• Enterococcus faecium is a significant cause of hospital-acquired infections.
• Vancomycin is a critical antibiotic for treating serious Gram-positive bacterial infections.
• Emergence of vancomycin resistance in E. faecium poses a major public health threat.

Purpose of the Study:

• To identify and characterize novel van gene clusters in clinical Enterococcus faecium isolates.
• To investigate the genetic context and potential origin of the identified van gene cluster.
• To assess the clinical relevance of van gene screening in E. faecium.

Main Methods:

• Whole-genome sequencing of a clinical Enterococcus faecium isolate.
• Bioinformatic analysis to identify and characterize the van gene cluster.
• Comparative genomics to infer the origin of the mobile genetic element.

Main Results:

• Identification of a novel van operon cluster (4,589 bp) containing the vanP ligase gene.
• The van gene cluster is located on a putative novel integrative conjugative element within a ~98 kb genomic region.
• Evidence suggests horizontal gene transfer from Clostridium scidens and Roseburia sp. 499.
• The isolate exhibited a vancomycin minimum inhibitory concentration (MIC) of 4 µg/mL.

Conclusions:

• A novel van gene cluster, potentially acquired via horizontal gene transfer, was identified in Enterococcus faecium.
• The findings highlight the dynamic nature of antimicrobial resistance gene acquisition in bacteria.
• Routine screening for van genes in E. faecium strains with borderline vancomycin susceptibility is recommended to monitor resistance.
• This discovery contributes to understanding the evolution and dissemination of vancomycin resistance.