The False Statement is E
Statement E is FALSE: Enterococci are a well-established cause of urinary tract infections, making this the incorrect statement among the options provided. 1, 2, 3, 4, 5
Analysis of Each Statement
A) Most Common Species: E. faecium and E. faecalis - TRUE
Both Enterococcus faecalis and E. faecium are indeed the predominant species causing human infections. Recent data shows E. faecalis accounts for approximately 46.7% and E. faecium 53.3% of enterococcal isolates, though E. faecalis historically represents the majority of clinical infections 1. These two species are responsible for the vast majority of enterococcal infections in clinical practice 5.
B) Can Cause Bacteremia and Endocarditis - TRUE
Enterococci are well-documented causes of both bacteremia and infective endocarditis. Guidelines specifically address enterococcal endocarditis treatment, noting that E. faecium endocarditis carries higher mortality than E. faecalis 6, 7. Recent case reports confirm enterococcal bacteremia can lead to subacute infective endocarditis, particularly following urological procedures 2.
C) Ampicillin Preferred for Susceptible Strains - TRUE
Ampicillin is definitively the drug of choice for ampicillin-susceptible enterococcal infections 7. Guidelines recommend ampicillin-based regimens for susceptible strains, including combination therapy with gentamicin or ceftriaxone for endocarditis 6. Even for vancomycin-resistant E. faecalis, 82% remain ampicillin-susceptible, supporting ampicillin as first-line therapy when susceptibility is confirmed 8.
D) Linezolid Preferred for Vancomycin-Resistant Strains - TRUE
Linezolid is FDA-approved specifically for vancomycin-resistant Enterococcus faecium infections, including concurrent bacteremia 9. Guidelines recommend daptomycin (8-12 mg/kg) as preferred for serious VRE infections due to bactericidal activity, with linezolid as an alternative 7. For VRE urinary tract infections, linezolid remains the most reliable oral option for E. faecium (>90% susceptible), though daptomycin is most commonly used in practice 4, 8.
E) Never Cause UTIs - FALSE
This statement is categorically incorrect. Urinary tract infections are the most common nosocomial infection caused by enterococci 5. Recent surveillance data confirms:
- UTIs account for 67% of enterococcal infections in hospitalized patients 1
- Enterococci represent 6-7% of culture-positive urine specimens 1, 3
- Both E. faecalis and E. faecium are established uropathogens 4
- UTIs are particularly associated with instrumentation and antimicrobial resistance 5
Clinical Pitfalls
Common mistake: Assuming vancomycin resistance implies ampicillin resistance. VRE E. faecalis remains 82-90% ampicillin-susceptible because resistance mechanisms differ (vanA/vanB operons vs. altered penicillin-binding proteins) 8. High-dose ampicillin can overcome resistance in UTIs due to urinary drug concentrations 7.
Overtreatment concern: Despite ampicillin susceptibility in VRE E. faecalis, daptomycin is the most frequently prescribed agent (19% of cases), representing potential antimicrobial overuse 8.