Sequential regimen for early post-surgical infective endocarditis due to methicillin-resistant Staphylococcus aureus (MRSA), unresponsive to standard antibiotic therapy: a case report

Daptomycin Use After Vancomycin-Induced Neutropenia in a Patient with Left-Sided Endocarditis

Objective:

To report a positive outcome in a patient treated with daptomycin for left-sided endocarditis associated with methicillin-resistant Staphylococcus aureus (MRSA) subsequent to vancomycin-induced neutropenia.

Case Summary:

A 55-year-old African American male was diagnosed with left-sided endocarditis, brain abscesses, and septic arthritis due to community-acquired MRSA. He began treatment with intravenous vancomycin to achieve a trough concentration of 15–20 μg/mL and oral rifampin 600 mg/day. A repair and resection of the mitral valve was completed on day 15 of hospitalization. Vancomycin was discontinued on day 36 secondary to drug-induced neutropenia (absolute neutrophil count nadir 162 cells/μL). Intravenous therapy with daptomycin 6 mg/kg every 24 hours was then initiated and the neutropenia resolved. The patient was discharged from the hospital on day 56.

Discussion:

Upon discontinuation of vancomycin, treatment options were limited to a small number of alternatives. Documented clinical experience and relevant studies are limited regarding the use of quinupristin/dalfopristin (Q/D), linezolid, trimethoprim/sulfamethoxazole (TMP/SMX), and daptomycin for the treatment of MRSA left-sided endocarditis. Daptomycin was selected because of its bactericidal qualities and its recent approval for this indication. The prognostic outlook for use of daptomycin in this treatment was uncertain; however, Q/D, linezolid, and TMP/SMX posed greater risks of failure.

Conclusions:

Treatment of MRSA left-sided endocarditis in patients intolerant to vancomycin is challenging. The positive outcome in our patient is likely attributable to aggressive vancomycin dosing and extended duration of treatment prior to the initiation of daptomycin. The use of daptomycin in this case enabled successful management of left-sided endocarditis.

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.

Successful treatment of MRSA native valve endocarditis with oral linezolid therapy: a case report

Staphylococcal endocarditis is potentially fatal and is now the most common cause of infective endocarditis with a mortality rate of 25-47% [Hecht SR, Berger M. Right-sided endocarditis in intravenous drug users: prognostic features in 102 episodes. Ann Intern Med 1992;117:560-6]. Its treatment requires maintenance of bactericidal level of antibiotics for prolonged periods to attain a culture-negative state. Although intravenous vancomycin is currently the drug of choice for methicillin resistant Staphylococcus aureus (MRSA) endocarditis, we present a case treated successfully with oral linezolid for 4 weeks due to a lack of venous access.

The Staphostatin-staphopain complex: a forward binding inhibitor in complex with its target cysteine protease

Staphostatins are the endogenous inhibitors of the major secreted cysteine proteases of Staphylococcus aureus, the staphopains. Our recent crystal structure of staphostatin B has shown that this inhibitor forms a mixed, eight-stranded beta-barrel with statistically significant similarity to lipocalins, but not to cystatins. We now present the 1.8-A crystal structure of staphostatin B in complex with an inactive mutant of its target protease. The complex is held together through extensive interactions and buries a total surface area of 2300 A2. Unexpectedly for a cysteine protease inhibitor, staphostatin B binds to staphopain B in an almost substrate-like manner. The inhibitor polypeptide chain runs through the protease active site cleft in the forward direction, with residues IG-TS in P2 to P2' positions. Both in the free and complexed forms, the P1 glycine residue of the inhibitor is in a main chain conformation only accessible to glycines. Mutations in this residue lead to a loss of affinity of the inhibitor for protease and convert the inhibitor into a substrate.

Successful use of oral linezolid as a single active agent in endocarditis unresponsive to conventional antibiotic therapy

Treatment of resistant gram-positive endocarditis is difficult. We report a case of resistant Staphylococcus epidermidis endocarditis that failed to respond to conventional antibiotic therapy but was treated successfully with an oral regimen of a new antibiotic, linezolid as a single active agent. This case report demonstrates the use of linezolid as an effective alternative to conventional antibiotics in such cases.