Gram positive cocci, often in pairs. E. faecalis and E. faecium are the big two, as well as E. avium, E. casseliflavus, E. durans, E. gallinarum, E. hira, E. raffinosus.
Normal bowel flora.
UTI and blood stream infections are most common ICU line related bacteremias have a high incidence (almost 50%) of both MOSF and death (PubMed), although patients may be dying with it rather than of it (PubMed).
But its only one positive culture. Doesn't matter. One or many, enterococcus does not belong in the blood (PubMed). Treat it.
Worst disease is endocarditis and always suspect it when there are positive blood cultures, even if you have a source (PubMed). The risks are monomicrobial E. faecalis bacteremia, community acquisition, prosthetic heart valve, and males (Pubmed).
Half of Enterococcal endocarditis patients will have a colonic neoplasm so they require a colonoscopy(PubMed). The patient not the enterococcus.
E. faecalis, E. faecium: usually ampicillin, vancomycin, linezolid, daptomycin, or quinupristin/dalfopristin. If vancomycin resistant (VRE) use linezolid, daptomycin, or quinupristin/daptomycin; I use them in that order. What data there is suggests linezolid is better than daptomycin for bacteremia VRE (PubMed).
Although a retrospective analysis show little difference between linezolid and daptomycin for VRE blood stream infections (PubMed)(PubMed), others show superiority of linezolid (PubMed) and others the superiority of daptomycin (PubMed). If Newton had been a doctor, he would say that for every study there is an equal and opposite study.
Failure may occur depending in genotype, even if it appears sensitive in the lab (PubMed). Sometimes I wish I could somehow safely autoclave the patient to get rid of some of these bugs.
Endocarditis: For high level gentamicin resistance and gentamicin susceptible, ampicillin 12 grams a day PLUS ceftriaxone 2 gm q 12 for 6 to 8 weeks actually works (PubMed) and is probably the treatment of choice (PubMed).
The old school is 6 weeks of ampicillin (preferred; 12 grams a day) PLUS an aminoglycoside OR vancomycin PLUS an aminoglycoside no matter what it does to the ears or kidneys (although the risk for gentamicin toxicity may be genetic). If patients have been ill less than three months, 4 week may be enough. Beware of high level gentamicin resistance (MIC > 500).
Maybe, for VRE, use daptomycin PLUS ampicillin for 8 to 10 weeks or quinupristin/dalfopristin for 6 weeks or linezolid or daptomycin (high dose) WITH tigecycline. Best bet is to right to valve replacement.
When part of mixed flora I tend to ignore it as when you treat and debride the other infections, the enterococcus tends to go away (although, being resistant to ALL cephalosporins, over growth with occasional bacteremia is a known complication of cephalosporin based therapies).
Arthritis: If the prosthetic joint is infected with Enterococcus, monotherapy is equal to combination (PubMed). If you have VRE, there is no difference between linezolid or quinupristin/dalfopristin in terms of outcome (PubMed). Other enterococci have variable resistance and need to be checked for antibiotic susceptibility.
The big problem with the enterococcus is not that it is very virulent. It tends to be found in dead tissues or people who are soon to become dead tissue.
The other big problem is resistance, and no one expects the Spanish inquisition: no single antibiotic can kill it, which is why you have to give combination therapy to cure endocarditis. Vancomycin resistance (VRE), which occurs in at least four forms, is a bigger worry, again, not because it is all that virulent, but because the organism serves as a reservoir for resistance in S. aureus; these genes have jumped from endocarditis to S. aureus at least twice and will do so again.
Evolution progresses apace: E. faecium has acquired beta-lactamases (PubMed). Crap.
A curiosity: stool transplants for C. difficile gets rid of VRE (Pubmed). I am sure that has some profound consequences in understanding the bowel biome.