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Distribution of putative virulence markers in Enterococcus faecium: towards a safety profile review

Ana R Freitas1, Ana P Tedim2,3,4, Carla Novais1

  • 1UCIBIO/REQUIMTE, Departamento de Ciências Biológicas, Laboratório de Microbiologia, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.

The Journal of Antimicrobial Chemotherapy
|November 18, 2017
PubMed
Abstract

Insights

The European Food Safety Authority (EFSA) is debating criteria for safe Enterococcus faecium (Efm) feed additives. This study identified new putative virulence markers (PVM) in Efm strains, improving public health risk assessments for animal nutrition.

Area of Science:

  • Microbiology
  • Food Safety
  • Public Health

Background:

  • The European Food Safety Authority (EFSA) is currently evaluating criteria for identifying Enterococcus faecium (Efm) strains capable of causing human infections.
  • Current safety assessments for Efm used as feed additives consider ampicillin susceptibility and the absence of specific genes (IS16/esp/hyl), but lack comprehensive data on other putative virulence markers (PVM).
  • Understanding the distribution of PVM in Efm is crucial for accurate risk assessment and ensuring the safety of Efm strains in animal nutrition and public health.

Purpose of the Study:

  • To analyze the distribution of major putative virulence markers (PVM) and ampicillin resistance phenotypes in large collections of Enterococcus faecium (Efm) strains.
  • To investigate the association between PVM and ampicillin resistance in Efm.
  • To assess the safety of Efm strains from a public health perspective by identifying reliable infection markers.

Main Methods:

  • Assessed 33 PVM using PCR/sequencing in 328 clonally diverse Efm strains collected between 1986 and 2015.
  • Determined ampicillin susceptibility via Etest and broth microdilution according to EUCAST guidelines.
  • Analyzed clonal relationships using Multi-Locus Sequence Typing (MLST) and the genomic location of PVM via S1-PFGE/hybridization.

Main Results:

  • Infection-derived Efm strains showed a higher prevalence of PVM, with increased ampicillin Minimum Inhibitory Concentration (MIC) positively correlating with a greater diversity of PVM.
  • Specific PVM associated with surface proteins (esp/sgrA/ecbA/acm), colonization (hyl/ptsD/orf1481), and genetic plasticity (IS16) were enriched in clinical Efm, primarily clade A1, but also found in clades A2/B.
  • The gene ptsD was identified as a reliable marker for ampicillin-resistant Efm; ptsD, IS16, orf1481, sgrA, and hospital-acquired pili gene clusters are proposed as safety assessment markers.

Conclusions:

  • This study expands the understanding of PVM distribution across diverse Efm lineages.
  • It highlights the presence of significant Efm infection markers not currently included in EFSA's safety criteria.
  • The identified markers can significantly impact the risk assessment of Efm strains, contributing to enhanced public health protection.

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