The Many Faces of Enterococcus spp.—Commensal, Probiotic and Opportunistic Pathogen

Abstract

Enterococcus spp. are Gram-positive, facultative, anaerobic cocci, which are found in the intestinal flora and, less frequently, in the vagina or mouth. Enterococcus faecalis and Enterococcus faecium are the most common species found in humans. As commensals, enterococci colonize the digestive system and participate in the modulation of the immune system in humans and animals. For many years reference enterococcal strains have been used as probiotic food additives or have been recommended as supplements for the treatment of intestinal dysbiosis and other conditions. The use of Enterococcus strains as probiotics has recently become controversial due to the ease of acquiring different virulence factors and resistance to various classes of antibiotics. Enterococci are also seen as opportunistic pathogens. This problem is especially relevant in hospital environments, where enterococcal outbreaks often occur. Their ability to translocate from the gastro-intestinal tract to various tissues and organs as well as their virulence and antibiotic resistance are risk factors that hinder eradication. Due to numerous reports on the plasticity of the enterococcal genome and the acquisition of pathogenic microbial features, we ask ourselves, how far is this commensal genus from acquiring pathogenicity? This paper discusses both the beneficial properties of these microorganisms and the risk factors related to their evolution towards pathogenicity.

Amelioration of growth, nutritional value, and microbial load of Tenebrio molitor (Coleoptera: Tenebrionidae) through probiotic supplemented feed

“…Although all probiotics present immuno-stimulatory action, E. faecalis is a commensal bacterium that is present in significant numbers in the intestinal microbiome. Therefore, the modulation of the immune system in humans and animals is significant and E. faecalis has proven a better competitor compared to lactic acid bacteria regarding intestinal colonization [49]. A healthy homeostasis and beneficial effects on the intestinal tract are naturally and efficiently preserved by the use of commensal bacteria as probiotics, namely Next-Generation Probiotics (NGP) [50].…”

Deconstructing the role of iron and heme in the structure of healthy human gut microbial communities

“…Iron deprivation did not have detrimental effects on the Enterococcaceae and Burkholderiaceae families, which are low-abundance yet prevalent members of the human gut microbiome and are largely understudied. Most knowledge about the Enterococcaceae focuses on pathogenesis, and specifically on infection by the opportunistic pathogen Enterococcus faecalis (Keogh et al, 2016; Krawczyk et al, 2021; Saillant et al, 2021). Literature on iron responses of the Burkholderiaceae family is almost nonexistent (Hiippala et al, 2016).…”

Designing a novel multi-epitope vaccine to evoke a robust immune response against pathogenic multidrug-resistant Enterococcus faecium bacterium

“…Enterococcus faecium is among the most frequent causes of healthcare-associated infections with underlying co-morbidities such as UTIs, intra-abdominal infection, prostatitis, organ transplantation, diabetes, endocarditis [ 1 ]. E. faecium is also reported as the second most prevalent organism involved in bloodstream infections and rank fourth in terms of surgical site infections in the US and European hospitals [ 2 , 3 ]. Cassini et al reported 16,146 instances of vancomycin-resistant enterococcal infections and 1081 related fatalities in Europe in 2015 [ 4 ].…”