Non- faecium non- faecalis enterococci: a review of clinical manifestations, virulence factors, and antimicrobial resistance

Abstract

SUMMARYEnterococci are a diverse group of Gram-positive bacteria that are typically found as commensals in humans, animals, and the environment. Occasionally, they may cause clinically relevant diseases such as endocarditis, septicemia, urinary tract infections, and wound infections. The majority of clinical infections in humans are caused by two species: Enterococcus faecium and Enterococcus faecalis. However, there is an increasing number of clinical infections caused by non-faecium non-faecalis (NFF) enterococci. Although NFF enterococcal species are often overlooked, studies have shown that they may harbor antimicrobial resistance (AMR) genes and virulence factors that are found in E. faecium and E. faecalis. In this review, we present an overview of the NFF enterococci with a particular focus on human clinical manifestations, epidemiology, virulence genes, and AMR genes.

Keywords: Enterococcus; antimicrobial resistance; virulence factors.

Fig 1

Non-faecium non-faecalis enterococci and the host/environments from which they are most frequently isolated.

Fig 2

The prevalence of non-faecium non-faecalis Enterococcus infections among all enterococcal infections worldwide (16–37). Non-faecium non-faecalis Enterococcus infection data from all countries were collected from continuous national surveillance, except for Malawi (only from one health center). Four countries (Norway, Spain, New Zealand, and Australia) identified the isolates down to the species level. The remaining countries identified the isolates as enterococci not belonging to E. faecium or E. faecalis.