Staphylococcal endocarditis—recommendations for therapy

Infective Endocarditis in Intravenous Drug Abusers

Infective endocarditis (IE) is one of the most severe complications in intravenous drug abusers (IVDA). IE usually involves the tricuspid valve, Staphylococcus aureus is the most common etiologic agent, and it has a relatively good prognosis. Currently, between 40% and 90% of IVDA with IE are HIV infected, and the HIV epidemic has caused a decrease in the incidence of this disease, probably due to changes in drug administration habits undertaken by addicts in order to avoid HIV transmission. This review focuses on progress made over the past few years in some aspects of IE in IVDA. The pathogenesis of tricuspid endocarditis is still unknown more than 60 years after the first series. The most important advance in antibiotic therapy is that noncomplicated S. aureus right-sided endocarditis can be successfully treated with an intravenous 2-week course of nafcillin or cloxacillin plus an aminoglycoside, although probably the aminoglycoside administration could be stopped after the first 3 to 5 days. Surgery in HIV-infected IVDA with IE does not worsen the prognosis. Considering the possibility of reinfection in IVDA, prosthetic material is usually avoided. Tricuspid valvulectomy or valve repair should be considered the technique of choice in IVDA with right-sided IE. Replacement of the tricuspid valve by a cryopreserved mitral homograft is the latest introduction into clinical practice. It provides atrioventricular competence, thereby avoiding late right heart failure. Reinfections can be treated medically with a negligible reoperation rate. Overall mortality for HIV-infected or non-HIV-infected IVDA with IE is similar. However, among HIV-infected IVDA, mortality is significantly higher in those who are most severely immunosuppressed, with CD4(+) cell counts below 200/L or with AIDS criteria.

Infective endocarditis and cardiac surgery in intravenous drug abusers and HIV-1 infected patients

Infective endocarditis (IE) is one of the most severe complications of parenteral drug abuse. The incidence of IE in intravenous drug abusers (IVDAs) is 2% to 5% per year, being responsible for 5% to 10% of the overall death rate. The prevalence of HIV infection among IVDAs with IE ranges between 30% and 70% in developed countries and HIV-infection by itself increases the risk of IE in IVDAs. The incidence of IE in IVDAs is currently decreasing in some areas, probably due to changes in drug administration habits by addicts to avoid HIV transmission. Overall, Staphylococcus aureus is the most common etiological agent, being usually sensitive to methicillin (MSSA). The tricuspid valve is the most frequently affected (60% to 70%), followed by the mitral and aortic valves (20% to 30%). HIV-positive IVDAs have a higher ratio of right-sided IE and S aureus IE than HIV-negative IVDAs. Response to antibiotic therapy is similar. Drug addicts with non-complicated MSSA right-sided IE can be treated with an i.v. short-course regimen of nafcillin or cloxacillin for 2 weeks, with or without addition of an aminoglycoside during the first 3 to 7 days. The prognosis of right-sided endocarditis is generally good; overall mortality is less than 5%, and with surgery is less than 2%. In contrast, the prognosis of left-sided IE is less favorable; mortality is 20% to 30%, and even with surgery is 15% to 25%. IE caused by GNB or fungi has the worst prognosis. Mortality between HIV-infected or non-HIV-infected IVDAs with IE is similar. However, among HIV-infected IVDAs, mortality is significantly higher in those who are most severely immunosuppressed, with CD4+ cell count < 200/microL or with AIDS criteria. Conversely, IE in HIV-infected patients who are not drug abusers is rare. The epidemiology of cardiac surgery in IVDAs and/or HIV-infected patients has changed in recent years. There is a decrease in IE and an increase of patients undergoing surgery (CABS) for coronary artery disease secondary to the hyperlipidemia and lipodystrophy induced by highly active antiretroviral therapy (HAART). Cardiac surgery in HIV-infected patients with or without IE does not worsen the prognosis because extracorporeal circulation did not affect the immune status after surgery. Morbidity and mortality seems to stay within the same range as the non-infected patients. In our experience, in the IE in HIV-infected IVDA group, the 1-year survival is 65% and the 5 and 10-year actuarial survival is 35%. For patients operated on for coronary artery disease, the 5-year survival is 100%.

The changing clinical aspects of infective endocarditis: descriptive review of 90 episodes in a French teaching hospital and risk factors for death

OBJECTIVE

We wanted to describe the epidemiological aspects of infective endocarditis (IE) in a French hospital and identify the prognostic factors.

METHODS

We reviewed the clinical, echocardiographic and microbiological features, and the outcome of 89 patients (90 episodes, median age 60 years) with IE over 18 months. Logistic regression analysis was used to identify prognostic factors for death.

RESULTS

A native valve was involved in 68 cases (75.5%); in 7 of these the patient was an intravenous drug user. A prosthetic valve was involved in 22 cases (24.5%); 5 of these were of early onset. Diagnosis was definite in 87% of cases. Median time to diagnosis was 3 days. Twenty-five patients (28%) were immunocompromised. A portal of entry, usually cutaneous, was identified in 65% of cases. Sixty-two percent of patients had an underlying heart disorder, usually degenerative. The infection involved the left heart in more than 75% of cases. One or more vegetations were detected in 75% of cases. The median size of vegetation was 15 mm. Isolated agents were mainly staphylococci (n=40 (44%), including 12 coagulase-negative isolates), and streptococci (n=23 (25%), including 7 enterococci). In 11 cases (12%), cultures remained negative. Nineteen episodes were nosocomial and Staphylococcus aureus was implicated in 11 of them. Fifty percent of patients had at least one complication: heart failure (n=42), kidney failure (n=44), embolism (n=35), septic shock (n=19). Surgery was performed in 49 cases (54%) due to heart failure (n=19), cerebral embolism (n=12), and/or severe valve lesions (n=27). Eighteen patients died, 10 of whom were infected with S. aureus. Nosocomial IE (P=0.0008), heart failure (P=0.004) and prosthetic valve (P=0.01), but not S. aureus were independently associated with death.

CONCLUSIONS

S. aureus was the main microorganism isolated in our patients. However, it was not independently predictive of fatal outcome.

Combination of quinupristin-dalfopristin and gentamicin against methicillin-resistant Staphylococcus aureus: experimental rabbit endocarditis study

The combination of quinupristin-dalfopristin (Q-D) and gentamicin was tested against two strains of gentamicin- and dalfopristin-susceptible methicillin-resistant Staphylococcus aureus (MRSA). One strain was susceptible to macrolides, lincosamides, and streptogramin B type antibiotics (MLS(B)), and the other was constitutively resistant to these antibiotics by virtue of the ermA gene. The checkerboard method and time-kill curves showed that the combination of Q-D and gentamicin was indifferent. A rabbit endocarditis model simulated the pharmacokinetics achieved in humans receiving intravenous injections of Q-D (7.5 mg/kg of body weight three times a day) and gentamicin (3 mg/kg once daily). For the MLS(B)-susceptible strain, a 4-day regimen reduced mean bacterial titers (MBT) in vegetations from 8.5 +/- 0.8 log CFU/g (control group) to 4.1 +/- 2.6 (gentamicin), 3.0 +/- 0.9 (Q-D), and 2.6 +/- 0.5 log CFU/g (Q-D plus gentamicin). For the strain constitutively resistant to MLS(B), a 4-day regimen reduced MBT in vegetations from 8.7 +/- 0.9 log CFU/g (control group) to 5.0 +/- 2.2 (gentamicin), 5.2 +/- 2.2 (Q-D), and 5.1 +/- 2.4 log CFU/g (Q-D plus gentamicin). The differences between control and treatment groups were significant for both strains (P < 0.0001), although there was no significant difference between treatment groups. No resistant variant was isolated from vegetations, and no significant difference in MBT in vegetations of treatment groups after 1-day regimens was observed. This experimental study found no additive benefit in combining Q-D and gentamicin against dalfopristin- and gentamicin-susceptible MRSA.

Infective endocarditis in intravenous drug abusers and HIV-1 infected patients

Infective endocarditis (IE) is one of the most severe complications of parenteral drug abuse. The incidence of IE in intravenous drug abusers (IVDAs) is 2% to 5% per year, being responsible for 5% to 20% of hospital admissions and 5% to 10% of the overall death rate. IVDAs often develop recurrent IE. The prevalence of HIV infection among IVDAs with IE ranges between 30% and 70% in urban areas in developed countries. The incidence of IE in IVDAs is currently decreasing in some geographical areas, probably due to changes in drug administration habits undertaken by addicts in order to avoid HIV transmission. Overall, Staphylococcus aureus is the most common etiological agent, being in most geographical areas sensitive to methicillin (MSSA). The remainder of cases is caused by streptocococci, enterococci, GNR, Candida spp, and other less common organisms. Polymicrobial infection occurs in 2% to 5% of cases. The tricuspid valve is the most frequently affected (60% to 70%), followed by the mitral and aortic valves (20% to 30%); pulmonic valve infection is rare (< 1%). More than one valve is infected in 5% to 10% of cases. HIV-positive IVDAs have a higher ratio of right-sided IE and S. aureus IE than HIV-negative IVDAs. Response to antibiotic therapy is similar among HIV-infected or non-HIV-infected IVDAs. Drug addicts with non-complicated MSSA right-sided IE can be treated successfully with an i.v. short-course regimen of nafcillin or cloxacillin for 2 weeks, with or without addition of an aminoglycoside during the first 3 to 7 days. Surgery in HIV-infected IVDAs with IE does not worsen the prognosis. The prognosis of right-sided endocarditis is generally good; overall mortality is less than 5%, and with surgery less than 2%. In contrast, the prognosis of left-sided IE is less favorable; mortality is 20% to 30%, and even with surgery is 15% to 25%. IE caused by GNB or fungi has the worst prognosis. Mortality between HIV-infected or non-HIV-infected IVDAs with IE is similar. However, among HIV-infected IVDAs, mortality is significantly higher in those who are most severely immunosuppressed, with CD4+ cell count < 200/microL or with AIDS criteria. Finally, IE in HIV-infected patients who are not drug abusers is rare.

Special issues in the management of infective endocarditis caused by gram-positive cocci

Gram-positive cocci, mainly streptococci and staphylococci, continue to cause the majority of cases of infective endocarditis. Among the streptococci causing IE, the long-standing predominance of oral or viridans-group streptococci has progressively faded, while the number of cases caused by "enteric streptococci" (Streptococcus bovis and enterococci) has increased. While most oral streptococci and S. bovis strains remain fully sensitive to penicillin, nutritionally variant streptococci--now renamed Abiotrophia--and enterococci can exhibit resistance to penicillin and/or glycopeptides that makes endocarditis more difficult to treat. Among the staphylococci causing endocarditis, the increasing proportion of coagulase-negative and methicillin-resistant strains observed in recent years has changed the approach to choice of antibiotic therapy. The purpose of this paper is to focus on some new aspects of the management of antibiotic therapy of IE due to streptococci and staphylococci, including recent developments such as once-daily aminoglycoside administration in IE, outpatient antibiotic therapy, and the evaluation of new antibiotics.

New developments in the treatment of infective endocarditis infective cardiovasculitis

The natural history of infective endocarditis has undergone remarkable changes over the past 100 years as regards both the demographic characteristics of the disease and changes in the incidence of the so-called diagnostic signs. Alongside these changes and the development of new and better diagnostic tools and criteria, we are also facing new problems with the precise definition of cardiovascular infections and calculation of the incidence of the disease. Nosocomial endocarditis presents an emerging problem of diagnosis and treatment after heart valve surgery, with pace-maker catheters, defibrillators and a very large variety of foreign materials used in connection with heart valve surgery. New technological progress including new types of prosthetic valves and use of homografts or the Ross operation will give a greater possibility of choosing the best solution in a particular case. Antimicrobial chemotherapy is mainly based on our understanding of the pathophysiology of the disease and efficacy of the antibiotics achieved in an experimental animal model of endocarditis. Important recommendations of single or combined drug therapy or the dosing regimens of antibiotics are still an expression of expert opinion not always supported by experimental or clinical proof. A typical example is the recommendation of two divided doses of gentamicin for treatment of streptococcal endocarditis. Nevertheless, it is the author's opinion that the development of uncomplicated, easy to handle diagnostic and treatment regimens are justified in order to achieve better compliance with these recommendations.