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Publications

Journal Article Ppublish

PubMed: 42671072 DOI: 10.1002/mbo3.70393

Emergence of a Novel, Phenotypically Difficult-to-Detect Vancomycin-Resistant Enterococcus faecium Clone (ST117/CT7799).

Microbiologyopen 15(5):e70393

Authors: Patrick Forstner, Christine Uitz, Johanna Dabernig-Heinz, Gabriel E Wagner, Jennifer Bender, Martin Fischer, David Siebenhofer, Guido Werner, Tobias Busche, Levin Joe Klages, Christian Rückert-Reed, Ivo Steinmetz, Karl Dichtl

Affiliations

  • Diagnostic and Research Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria.
  • Division of Nosocomial Pathogens and Antibiotic Resistances, Department of Infectious Diseases, Robert Koch Institute, Wernigerode, Germany.
  • German National Reference Centre for Staphylococci and Enterococci, Wernigerode, Germany.
  • Medical Faculty OWL, Bielefeld University, Bielefeld, Germany.
  • Center for Biotechnology, Bielefeld University, Bielefeld, Germany.
  • Diagnostic and Research Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria. Institute of Laboratory Medicine and Microbiology, Protestant Hospital of Bethel Foundation, Campus Bielefeld-Bethel, University Hospital OWL of Bielefeld University, Bielefeld, Germany.

Abstract

A significant increase of vancomycin-resistant Enterococcus faecium (VREfm) infections was observed in South-Eastern Austria since 2024. The prolonged outbreak is caused by a novel vanB-VREfm clone (ST117/CT7799, "VREfm styr"). This study characterizes the atypical difficult-to-detect resistance phenotype and assesses the genomic relatedness of the isolates. Patient and outbreak characteristics were investigated including whole genome sequencing of the isolates. Sensitivity of broth microdilution (BMD), gradient tests (GT), disk diffusion (DD), and automated susceptibility testing (VITEK2) was compared. The performance of commercial screening media was evaluated. From sporadic detections in early 2024 case numbers began to rise during the year. In 30/31 (97%) of all cases, intra-hospital transmission was considered likely and an association with invasive procedures was identified in most cases. Core genome multilocus sequence typing revealed only six allelic differences between VREfm styr isolates collected in a 12-month period, all belonging to the E. faecium ST117/CT7799 lineage. BMD detected vancomycin resistance (MIC > 4 mg/L) in no more than 16/31 (52%) of isolates after 24 h incubation, while GT and DD misclassified all isolates. Only prolonged incubation improved the performance of these assays. VITEK2 analysis, however, correctly classified all 31 isolates. Of four commercially available VRE-screening agars, only one was capable of detecting VREfm styr after 24 h incubation. The emergence and clonal dissemination of VREfm ST117/CT7799 reveals a serious diagnostic gap as commonly used diagnostic algorithms fail to reliably detect this resistance phenotype. Our findings should help to further evaluate the true geographical distribution and clinical significance of this novel VREfm clone.

MeSH

Vancomycin Resistance, Phenotype, Genome, Enterococcus Faecium, Enterococcus, Vancomycin, Clone Cells