Infectious disease

Enterococcus song

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Enterococcus

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Key points in this song10

Enterococci (E. faecalis and E. faecium) are gram-positive cocci in pairs or chains that are catalase-negative and PYR-positive, distinguishing them from Streptococci.
Enterococci are optochin-resistant and bile-esculin positive, growing in 6.5% NaCl — key lab features that differentiate them from Streptococcus bovis.
E. faecalis is the most common clinical isolate; E. faecium carries a higher rate of antibiotic resistance, including vancomycin-resistant Enterococcus (VRE).
Enterococci are part of normal GI flora and cause opportunistic infections, especially in hospitalized, immunocompromised, or debilitated patients.
Classic infections include UTIs, subacute bacterial endocarditis (particularly in patients with prior GI or GU procedures), biliary tract infections, and intra-abdominal abscesses.
Enterococcal endocarditis classically involves the mitral or aortic valve and requires synergistic bactericidal therapy with ampicillin plus gentamicin (or ampicillin plus ceftriaxone for aminoglycoside-resistant strains).
VRE harbors vanA or vanB resistance genes; vanA confers resistance to both vancomycin and teicoplanin, while vanB is resistant to vancomycin alone.
Treatment of VRE infections relies on linezolid or daptomycin; linezolid is bacteriostatic, while daptomycin is bactericidal.
Enterococci are intrinsically resistant to cephalosporins, clindamycin, and low levels of penicillin — monotherapy with beta-lactams is often insufficient for serious infections.
Enterococcus faecalis produces a cytolysin and gelatinase virulence factors, contributing to biofilm formation on prosthetic devices and increased pathogenicity in healthcare settings.