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Background: Vancomycin-resistant Enterococcus faecium (VREfm) prevalence greatly varies in European countries yet continues to rise [1]. We aimed to characterize clinical-VREfm from a local hospital (800-beds) during 2009-2021. Methods: VREfm [n=175; mostly from urine (40%)] were collected from medical-47% and surgical-32% wards. Antibiotic-resistance (ABR) and occurrence of vanA/vanB, plasmids [rep-pLG1/rep-pRUM/rep-Inc18(rep1/rep2)] and virulence genes were screened by disk-diffusion/broth-microdilution (EUCAST/CLSI) and PCR, respectively. Representative VREfm/year (n=81) were selected for MLST+WGS (Illumina-NovaSeq) and analysed through CGE-tools (homemade virulence and bacteriocins(bac) databases) and cgMLST/Ridom-SeqSphere+. Results: All isolates were resistant to glycopeptides [98%-vanA;2%-vanB], ampicillin, ciprofloxacin, erythromycin [erm(B)/msr(C)], less to gentamicin (49%;aac(6’)-Ie-aph(2’’)-Ia), tetracycline [27%; tet(M)/tet(L)], quinupristin-dalfopristin (5%) and/or linezolid (2%;GT2576 mutation). VREfm were oligoclonal (until 7 STs/year), mostly clustering into ST117-31%, ST78-19% and ST80-12%. For each ST, different complex-types (CT) were detected each year, but some were identified in different wards from 3-months (ST412-CT258/ST117-CT4659) to 2-4-years (ST117-CT24/CT6602/CT6603; ST78-CT330). Sequenced VREfm showed slight overlap (ST117-CT24 and ST78-CT230) with other global Efm. Recent years (>2019) concentrated the majority of novel CTs, without common clones over time, and ST494 (associated with a German outbreak) was introduced. ABR and virulence patterns were similar throughout the years. Bac-profiles (13 patterns) were similar between common STs/CTs. One new bacteriocin was detected >2017, Bac43 increased over time and BacAS9 was exclusively detected in ST117. The typical VREfm plasmidome [RepA_N-pRUM/pLG1-like, Inc18, Rep3-pB82/pEF418, Rep_Trans-pEFNP1/pRI1] was observed across the years however, Rep-pRUM decreased. A novel RepA_N-replicase (69% nucleotide identity with pRUM) was identified in most VREfm during 2009-2021. In silico analysis showed its occurrence in ~100 Efm-genomes/GenBank from different countries after 2000. Conclusion: Current clinical VREfm display a strong oligoclonal nature. Nosocomial transmission events and/or import of VREfm from colonized patients may explain the long-term persistence of particular clones. The continuous flux between community and hospital clones may feed the emergence of new lineages/opportunities for adaption hampering classical infection control interventions., Scientific Letters, Vol. 1 No. Sup 1 (2023)

Vancomycin-resistant enterococci (VRE) have caused hospital outbreaks worldwide, and the vancomycin-resistance gene (vanA) has crossed genus boundaries to methicillin-resistant Staphylococcus aureus. Spread of VRE, therefore, represents an immediate threat for patient care and creates a reservoir of mobile resistance genes for other, more virulent pathogens. Evolutionary genetics, population structure, and geographic distribution of 411 VRE and vancomycin-susceptible Enterococcus faecium isolates, recovered from human and nonhuman sources and community and hospital reservoirs in 5 continents, identified a genetic lineage of E. faecium (complex-17) that has spread globally. This lineage is characterized by 1) ampicillin resistance, 2) a pathogenicity island, and 3) an association with hospital outbreaks. Complex-17 is an example of cumulative evolutionary processes that improved the relative fitness of bacteria in hospital environments. Preventing further spread of this epidemic E. faecium subpopulation is critical, and efforts should focus on the early disclosure of ampicillin-resistant complex-17 strains.

Resumo

Nowadays, six types of acquired vancomycin resistance in enterococci are known; however, only VanA and to a lesser extent VanB are widely prevalent. Various genes encode acquired vancomycin resistance and these are typically associated with mobile genetic elements which allow resistance to spread clonally and laterally. The major reservoir of acquired vancomycin resistance is Enterococcus faecium; vancomycin-resistant Enterococcus faecalis are still rare. Population analysis of E. faecium has revealed a distinct subpopulation of hospital-acquired strain types, which can be differentiated by molecular typing methods (MLVA, MLST) from human commensal and animal strains. Hospital-acquired E. faecium have additional genomic content (accessory genome) including several factors known or supposed to be virulence-associated. Acquired ampicillin resistance is a major phenotypic marker of hospital-acquired E. faecium in Europe and experience has shown that it often precedes increasing rates of VRE with a delay of several years. Several factors are known to promote VRE colonisation and transmission; however, despite having populations with similar predispositions and preconditions, rates of VRE vary all over Europe.