What is the most defining characteristic of Enterococcus faecium?

Enterococcus faecium is primarily recognized for its significant resistance to vancomycin, making option B the defining characteristic. This resistance is of major clinical relevance, as Enterococcus faecium can cause serious infections in patients, particularly in those who are immunocompromised or undergoing invasive procedures. The ability of this organism to survive despite the presence of vancomycin, an antibiotic that is typically used as a last resort for Gram-positive infections, presents challenges in treatment and underscores the importance of monitoring and understanding antibiotic resistance patterns.

In clinical settings, knowing the resistance profile of Enterococcus faecium helps inform appropriate antibiotic choice and guides the management of infections caused by this organism. While other characteristics might be true for Enterococcus faecium under certain circumstances, vancomycin resistance is a hallmark of this species, ensuring its recognition as a significant concern in healthcare settings.