Successful treatment of Enterococcus faecalis prosthetic valve endocarditis with linezolid

Enterococcal endocarditis revisited

The Enterococcus species is the third main cause of infective endocarditis (IE) worldwide, and it is gaining relevance, especially among healthcare-associated cases. Patients with enterococcal IE are older and have more comorbidities than other types of IE. Classical treatment options are limited due to the emergence of high-level aminoglycosides resistance (HLAR), vancomycin resistance and multidrug resistance in some cases. Besides, few new antimicrobial alternatives have shown real efficacy, despite some of them being recommended by major guidelines (including linezolid and daptomycin). Ampicillin plus ceftriaxone 2 g iv./12 h is a good option for Enterococcus faecalis IE caused by HLAR strains, but randomized clinical trials are essential to demonstrate its efficacy for non-HLAR EFIE and to compare it with ampicillin plus short-course gentamicin. The main mechanisms of resistance and treatment options are also reviewed for other enterococcal species.

Enterococcal endocarditis: can we win the war?

Treatment of enterococcal infections has long been recognized as an important clinical challenge, particularly in the setting of infective endocarditis (IE). Furthermore, the increase prevalence of isolates exhibiting multidrug resistance (MDR) to traditional anti-enterococcal antibiotics such as ampicillin, vancomycin and aminoglycosides (high-level resistance) poses immense therapeutic dilemmas in hospitals around the world. Unlike IE caused by most isolates of Enterococcus faecalis, which still retain susceptibility to ampicillin and vancomycin, the emergence and dissemination of a hospital-associated genetic clade of multidrug resistant Enterococcus faecium, markedly limits the therapeutic options. The best treatment of IE MDR enterococcal endocarditis is unknown and the paucity of antibiotics with bactericidal activity against these organisms is a cause of serious concern. Although it appears that we are winning the war against E. faecalis, the battle rages on against isolates of multidrug-resistant E. faecium.

Prosthetic valve endocarditis

Prosthetic valve endocarditis (PVE) is associated with a high mortality during the early and midterm follow-up despite diagnostic and therapeutic improvements; its incidence is increasing and reaches 20-30% of all infective endocarditis episodes. In this review, changes in epidemiology, microbiology, diagnosis and therapy that have evolved in the past few years are analyzed. Staphylococci (both Staphylococcus aureus and coagulase-negative Staphylococcus) have emerged as the most common cause of PVE and are associated with a severe prognosis. Moreover, diagnosis may often be difficult because of its complications and extracardiac manifestations; thus, a comprehensive assessment of the clinical, echocardiographic and laboratory data must be performed. Early PVE, comorbidity, severe heart failure and new prosthetic dehiscence are predictors of mortality. Therapy is not indicated by evidence-based recommendations but mostly on identification of the high-risk conditions. A PVE is a common indication for surgery, whereas medical treatment alone may be achieved in a few instances. Systematic prophylaxis should be used to prevent this severe complication of cardiac valve replacement.

Methicillin-resistant Staphylococcus epidermidis (MRSE) endocarditis treated with linezolid

Linezolid is not yet recognized as a standard therapy for infective endocarditis but its use becomes a necessity when infection is due to multidrug-resistant microorganisms. This report describes 1 patient with endocarditis treated with linezolid and 45 similar cases from the medical literature.

Linezolid for the treatment of drug-resistant infections

Multidrug-resistant pathogens have become increasingly common in contemporary healthcare. Specific to Gram-positive pathogens, methicillin-resistant Staphylococcus aureus (MRSA) is of particular concern, as it has been associated with increased hospital length of stay, higher healthcare expenditures and poorer outcomes. To date, linezolid is the first and only oxazolidinone approved by the US FDA for the treatment of infections caused by Gram-positive pathogens, including MRSA. This article will serve as a comprehensive review of linezolid, including an overview of the current market and its in vitro activity, with an in-depth review of its pharmacokinetic and pharmacodynamic profile. Emphasis will be placed on clinical data for the drug, both on- and off-label. The article will conclude with a brief overview of linezolid's pharmacoeconomic implications and safety profile, followed by a commentary and 5-year prospective analysis remarking on the future of the antimicrobial field as it relates to MRSA.

Linezolid therapy for infective endocarditis

Linezolid is not yet recognised as a standard therapy for infective endocarditis. This report describes nine patients with endocarditis treated with linezolid and 33 similar cases from the medical literature. The majority of cases involved multiresistant strains, and the reasons for administering linezolid were refractory disease (60%), intolerance (28%), sequential therapy (12%) and a resistant pathogen (1%). Linezolid was administered for a mean of 37 days, with a successful outcome in 79% of cases. Reversible adverse effects were described in ten cases. The mean follow-up period was 8.5 months. Further data from randomised controlled clinical trials are needed to determine the efficacy and safety of linezolid for treating endocarditis.

Cerebrospinal fluid penetration and bacteriostatic activity of linezolid against Enterococcus faecalis in a child with a ventriculoperitoneal shunt infection

We report a 4-year-old girl with a complicated Enterococcus faecalis ventriculoperitoneal shunt infection who failed vancomycin therapy. We demonstrate linezolid's high CSF penetration and its CSF bacteriostatic activity against E. faecalis. Linezolid may be a good alternative for treatment of ventriculoperitoneal shunt infections in cases of vancomycin-resistant organisms or apparent treatment failures.

Treatment of prosthetic valve infective endocarditis due to multi-resistant Gram-positive bacteria with linezolid

OBJECTIVES

Clinical experience with linezolid in the treatment of infective endocarditis either alone or in combination with other agents is limited. We describe our experience in the treatment of two patients with IE due to multi-resistant Gram-positive bacteria.

METHODS

One patient with MRSE and one with VRE endocarditis were treated with regimens containing linezolid. The killing kinetics of linezolid in combination with gentamicin or vancomycin against isolates of Staphylococcus epidermidis and Enterococcus faecalis were analysed in vitro.

RESULTS

Clinical response and eradication of bacteraemia was achieved with linezolid therapy in both patients. Time-kill curve studies showed that linezolid was bacteriostatic against the MRSE and VRE isolates used. Combination with gentamicin or vancomycin did not produce synergy or antagonism but at best only marginal additive effect.

CONCLUSIONS

Although bacteriostatic, linezolid provides an important therapeutic option in IE due to multi-resistant Gram-positive pathogens. It challenges the conventional wisdom that bactericidal synergy is required for the effective treatment of most cases of IE due to Gram-positive organisms.

Implant infections due to enterococci: role of capsular polysaccharides and biofilm

Enterococci are natural inhabitants of the gastrointestinal tract and of the female genital tract of humans and many animals. In recent years, enterococci have been increasingly recognized as important human pathogens causing infections associated with medical devices. Their resistance to most antimicrobial agents and their ability to form biofilm has contributed to the increasing incidence of nosocomial enterococcal infections. Enterococci possess a capsular polysaccharide composed of a glycerol-teichoic acid-like molecule consisting of repeating units of 6-alfa-D-glucose-1-2-glycerol-3-PO4 , substituted on carbon 2 with a alfa-2,1-linked molecule of glucose. Using both immunologic and genetic data E. faecalis can be assigned to specific serotypes based on capsular polysaccharides. Clinical examples of foreign-body infections due to enterococci are described, comprising infections of artificial joints, implanted intravascular catheters, artificial hearts and artificial valves, stents, liquor shunt devices, and intraocular infections. Methods to prevent and/or treat enterococcal infections are presented.

Antimicrobial agents for treatment of serious infections caused by resistant Staphylococcus aureus and enterococci

As clinicians increasingly contend with infections due to staphylococci or enterococci resistant to, or failing treatment with, traditional antimicrobial agents, understanding the potential roles of older as well as more recently introduced antimicrobial agents becomes important. Older agents, such as clindamycin and trimethoprim-sulfamethoxazole, have been used to treat infections due to community-acquired methicillin-resistant Staphylococcus aureus. Among the licensed agents, quinupristin-dalfopristin, linezolid, daptomycin, and tigecycline are active in vitro against most strains of methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecium, but these agents differ in their approved clinical indications. New agents currently under investigation may further expand treatment options.

Agents for the Treatment of Multidrug-resistant Gram-positive Endocarditis

Several newer agents with activity against multidrug- resistant gram-positive pathogens are available. These agents have in vitro and clinical data supporting their utility in the treatment of infections caused by pathogens such as methicillin-resistant staphylococci and vancomycin-resistant enterococci. Daptomycin appears to be rapidly bactericidal, and linezolid and quinupristin/dalfopristin also are cidal against staphylococci. Although the agents have several properties that are attractive for use in endocarditis, clinical data are limited. Further investigation with each agent and combination therapy are warranted before definitive recommendations can be made.

Infective endocarditis: a review of the best treatment options

Despite significant advances in antimicrobial therapy and an enhanced ability to diagnose and treat complications, infective endocarditis is still associated with substantial morbidity and mortality today, and its incidence has not decreased over the past decades. This apparent paradox may be explained by a progressive change in risk factors, leading to an evolution in its epidemiological and clinical features. In fact, new risk factors for endocarditis have emerged, such as intravenous drug abuse, diffusion of heart surgery procedures and prosthetic valve implantation, atherosclerotic valve disease in elderly patients, and nosocomial disease. Recently identified microorganisms (including Bartonella spp., Abiotrophia defectiva, and the HACEK group of bacteria [including Haemophilus spp., Actinobacillus spp., Cardiobacterium hominis, Eikenella corrodens and Kingella kingae]) are sometimes the cause of culture-negative endocarditis, and emerging resistant bacteria (such as methicillin- or vancomycin-resistant Staphylococci and vancomycin-resistant Enterococci) are becoming a new challenge for conventional antibiotic therapy. New therapeutic approaches need to be developed for the treatment of infective endocarditis caused by drug-resistant Gram-positive cocci, and some antimicrobial compounds recently introduced in clinical practice (such as streptogramins and oxazolidinones) may be an effective alternative, but further clinical studies are needed in order to confirm their effectiveness and safety. This review should help redefine the best therapeutic and preventive strategies against infective endocarditis.

Oxazolidinones: activity, mode of action, and mechanism of resistance

Oxazolidinones are a new group of antibiotics. These synthetic drugs are active against a large spectrum of Gram-positive bacteria, including methicillin- and vancomycin-resistant staphylococci, vancomycin-resistant enterococci, penicillin-resistant pneumococci and anaerobes. Oxazolidinones inhibit protein synthesis by binding at the P site at the ribosomal 50S subunit. Resistance to other protein synthesis inhibitors does not affect oxazolidinone activity, however rare development of oxazolidinone resistance cases, associated with 23S rRNA alterations during treatment have been reported. Linezolid, the first oxazolidinone available, has already taken its place in the clinic for treatment of Gram-positive infections. Pharmacokinetic properties as well as its good penetration and accumulation in the tissue including bone, lung, vegetations, haematoma and cerebrospinal fluid, allow its use for surgical infections.

Vancomycin-resistant Enterococcus faecium endocarditis in a premature infant successfully treated with linezolid

A 4 1/2-month-old, 26-week premature infant with multiple complications of prematurity required a central venous catheter for venous access and antibiotic treatment of bacterial nosocomial infections. He developed tricuspid valve endocarditis with vegetation caused by Enterococcus faecium resistant to ampicillin, vancomycin and quinupristin-dalfopristin but susceptible to linezolid. He was successfully treated with linezolid intravenously (7 weeks) and then orally (2 weeks).

Failure of linezolid treatment for enterococcal endocarditis

We describe a patient with Enterococcus faecalis endocarditis who failed to respond to treatment with linezolid.