Antibiotic resistance in Enterococcus faecium clinical isolates

Abstract

The worldwide ratio of Enterococcus faecalis-Enterococcus faecium infections is currently changing in favor of E. faecium. Intrinsic and acquired antimicrobial resistance traits of this latter species can explain this evolution as well as the diffusion of hospital-adapted strains belonging to the clonal complex CC17. Like other enterococci, E. faecium is naturally resistant to cephalosporins and aminoglycosides (at low level). Because of its high genome plasticity, it can also acquire numerous other resistances. It is noteworthy that most modern isolates of E. faecium are highly resistant to ampicillin while a non-negligible proportion of them (depending on geographical locations) are resistant to glycopeptides (especially in the USA). Even if resistance to newer antimicrobial agents (linezolid, daptomycin, tigecycline) is still uncommon, some clinical isolates with reduced susceptibility or resistance have already been reported and better understanding of resistance mechanisms is needed for prediction and prevention of their dissemination.

Keywords::

• antimicrobial resistance
• CC17
• E. faecium
• glycopeptide resistance
• VREF

Acknowledgement

The authors warmly thank A Hartke for critical reading of the manuscript and insightful comments.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Enterococcus faecium is becoming one of the leading causes of hospital-acquired infections. There is currently a shift in clinicalsignificance from Enterococcus faecalis to this species.

• The high genome plasticity of E. faecium is one of the major characteristics that may explain why it successfully adapt to harshconditions such as the hospital environment and how it can cope with antibiotic and antiseptic stresses.

• Its inherent resistance to antimicrobial agents such as cephalosporins and aminoglycosides (low level) as well as to its ability to acquireand share new antibiotic resistance traits (especially against ampicillin, gentamicin [high level] and vancomycin), causes more and more therapeutic problems.

• For the treatment of infections caused by vancomycin-resistant E. faecium (VREF) isolates, a limited arsenal is currently available butsome molecules (e.g., linezolid, daptomycin or tigecycline) can be alternative options. However, acquired resistance to these novel drugsis possible and has been already detected in vitro and in vivo.

• It is necessary to maintain the vigilance face to the dissemination of well hospital-adapted E. faecium strains (in particular, VREFbelonging to the clonal complex CC17) and to have rigorous policies of hygiene and antimicrobial use.