Enterococci are part of the normal intestinal flora. They used to be classified as group D streptococci but are now considered a separate genus. There are > 47 species, but E. faecalis and E. faecium most commonly cause infections in humans.
Enterococci typically cause
Intra-abdominal and pelvic infections
Skin, soft tissue, and wound infections
Treatment of Enterococcal Infections
Varies by site of infection and susceptibility testing
(See also the American Heart Association's 2015 Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications.)
Enterococci associated with endocarditis are difficult to eradicate unless a combination of certain cell wall–active antibiotics (eg, penicillin, ampicillin, amoxicillin, piperacillin, vancomycin) plus an aminoglycoside (eg, gentamicin, streptomycin) is used to achieve bactericidal activity. However, some cell wall–active antibiotics have limited or no activity against enterococci; they include nafcillin, oxacillin, ticarcillin, ertapenem, most cephalosporins, and aztreonam. E. faecium are more resistant to penicillin than E. faecalis. When an aminoglycoside cannot be used, the combination of an aminopenicillin, such as ampicillin, plus ceftriaxone is an effective alternative for the treatment of E. faecalis endocarditis. Imipenem and, to a lesser degree, meropenem are active against E. faecalis.
For complicated skin infections due to vancomycin-susceptible enterococci, daptomycin, linezolid, tedizolid, tigecycline, and omadacycline are effective treatment options.
Piperacillin/tazobactam, imipenem or meropenem, tigecycline, and eravacycline are recommended for complicated intra-abdominal infections when enterococci are known or presumed to be involved.
Urinary tract infections do not require bactericidal therapy and, if the causative organism is sensitive, are usually treated with a single antibiotic such as ampicillin or amoxicillin.
Resistance
In the past several decades, resistance to multiple antimicrobials has increased rapidly, especially among E. faecium.
Resistance to aminoglycosides (eg, gentamicin, streptomycin), particularly with E. faecium, continues to emerge.
Vancomycin-resistant enterococci (VRE) may also be resistant to other glycopeptides (eg, teicoplanin), aminoglycosides Aminoglycosides Aminoglycosides have concentration-dependent bactericidal activity. These antibiotics bind to the 30S ribosome, thereby inhibiting bacterial protein synthesis. Spectinomycin is a bacteriostatic... read more 
, and cell wall–active beta-lactams Beta-Lactams Beta-lactams are antibiotics that have a beta-lactam ring nucleus. Subclasses include Carbapenems Cephalosporins and cephamycins (cephems) Clavams Monobactams read more 
(eg, penicillin G, ampicillin). When identified, infected patients are strictly isolated. Recommended treatment includes streptogramins Lincosamides, Oxazolidinones, and Streptogramins Lincosamides ( clindamycin), oxazolidinones ( linezolid, tedizolid), and streptogramins ( dalfopristin [streptogramin A] and quinupristin [streptogramin B]) are structurally different but are... read more (quinupristin/dalfopristin Quinupristin and Dalfopristin Quinupristin and dalfopristin are streptogramin antibiotics, which, like macrolides and lincosamides, inhibit the synthesis of bacterial proteins. Quinupristin/dalfopristin (Q/D) is given together... read more for E. faecium only) and oxazolidinones Lincosamides, Oxazolidinones, and Streptogramins Lincosamides ( clindamycin), oxazolidinones ( linezolid, tedizolid), and streptogramins ( dalfopristin [streptogramin A] and quinupristin [streptogramin B]) are structurally different but are... read more (linezolid, tedizolid). Daptomycin, oritavancin, tigecycline, and eravacycline have in vitro activity against VRE and may be off-label treatment options. Nitrofurantoin and fosfomycin are often effective against vancomycin-resistant enterococcal urinary tract infection.
Beta-lactamase–producing enterococci are occasionally problematic, particularly when large numbers of organisms are present in tissues (eg, in endocarditis vegetation). Resistance may be present clinically even though the organism appears susceptible based on standard testing. Vancomycin or combination beta-lactam/beta-lactamase inhibitor antibiotics (eg, piperacillin/tazobactam, ampicillin/sulbactam) can be used.
Enterococci can incorporate exogenously produced folates and thereby reverse the effect of trimethoprim (TMP) and sulfamethoxazole (SMX); therefore, therapy with these antimicrobials may fail despite apparent in vitro susceptibility (for this reason, TMP/SMX is often left off of susceptibility panels for enterococci).
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
American Heart Association: Infective Endocarditis in Adults: Diagnosis, Antimicrobial Therapy, and Management of Complications (2015)
Drugs Mentioned In This Article
| Drug Name | Select Trade |
|---|---|
ampicillin |
Principen |
amoxicillin |
Amoxil, Dispermox, Moxatag, Moxilin , Sumox, Trimox |
vancomycin |
FIRVANQ, Vancocin, Vancocin Powder, VANCOSOL |
gentamicin |
Garamycin, Genoptic, Genoptic SOP, Gentacidin, Gentafair, Gentak , Gentasol, Ocu-Mycin |
streptomycin |
No brand name available |
nafcillin |
Nallpen |
oxacillin |
No brand name available |
ertapenem |
Invanz |
aztreonam |
Azactam, Cayston |
ceftriaxone |
Ceftrisol Plus, Rocephin |
meropenem |
Merrem |
daptomycin |
Cubicin, Cubicin RF |
linezolid |
Zyvox, Zyvox Powder, Zyvox Solution |
tedizolid |
SIVEXTRO |
tigecycline |
Tygacil |
omadacycline |
NUZYRA |
piperacillin/tazobactam |
Zosyn, Zosyn Powder |
eravacycline |
XERAVA |
penicillin g |
Pfizerpen |
oritavancin |
Kimyrsa, ORBACTIV |
nitrofurantoin |
Furadantin, Macrobid, Macrodantin, Urotoin |
fosfomycin |
Monurol |
ampicillin/sulbactam |
Unasyn |
trimethoprim |
Primsol, Proloprim, TRIMPEX |
