Endocarditis caused by Staphylococcus aureus: A reappraisal of the epidemiologic, clinical, and pathologic manifestations with analysis of factors determining outcome.

Staphylococcus aureus is the leading cause of infectious endocarditis and its mortality has remained high despite better diagnostic and therapeutic procedures over time. We conducted a retrospective review of 133 cases of definite S. aureus endocarditis seen at a single tertiary care hospital over 22 years to assess changes in the epidemiology and incidence of the infection, manifestations, outcome, risk factors for mortality, and impact of cardiac surgery on prognosis.Patients were classified into 2 groups: 1) right-sided endocarditis (64 patients) and 2) left-sided endocarditis (69 patients). While the number of cases of left-sided endocarditis remained steady at 1-3 cases per 10,000 admissions, the incidence of right-sided endocarditis, after a peak in the early 1990s, declined to almost disappear in 2001. Among the cases of right-sided endocarditis, we found 2 subsets of patients with different clinical features and prognosis: the first subset comprised 53 intravenous drug abusers, and the second subset comprised 11 patients with catheter-associated S. aureus bacteremia and endocarditis. Fifty-one patients were human immunodeficiency virus (HIV)-positive drug abusers, most of whom (80.3%) had right-sided endocarditis. We did not find differences in mortality between HIV-positive and HIV-negative individuals; mortality seemed to depend more on the site of the heart involved than on HIV status.Among the cases of left-sided endocarditis, the mitral valve was more commonly involved than the aortic valve (61% vs. 30%). Overall, 74% of patients with left-sided endocarditis developed 1 or more cardiac or extracardiac complication. In comparison, only 23.4% of patients with right-sided endocarditis developed complications.Prosthetic valve endocarditis (PVE) was hospital-acquired more frequently than native valve endocarditis (NVE). Patients with PVE had a shorter duration of symptoms until diagnosis and presented with or developed cardiac murmurs less frequently than patients with NVE. Cardiac failure (49%), renal failure (43%) and central nervous system (CNS) events (35%) were frequently observed in patients with both PVE and NVE. Valve replacement was more frequently needed and more rapidly performed in patients with PVE than in their counterparts with NVE.The overall mortality of patients with right-sided endocarditis was 17%. While the mortality of right-sided endocarditis in injection drug users was 3.7%, the mortality of patients with right-sided endocarditis associated with infected intravenous catheters was 82% (odds ratio [OR], 0.01; 95% confidence interval [CI], 0.001-0.07). For left-sided endocarditis mortality was 38% and was not significantly different in patients with NVE or PVE (OR, 0.65; 95% CI, 0.23-1.87). CNS complications were associated with mortality in both NVE (OR, 6.55; 95% CI, 1.78-24.04) and PVE (OR, 32; 95% CI, 2.63-465.40). Development of 2 or 3 complications was associated with an increased risk of mortality (OR, 5.59; 95% CI, 1.08-28.80 and OR, 9.25; 95% CI, 1.36-62.72 for 2 vs. 1 complication and for 3 vs. 2 complications, respectively).Surgical treatment did not significantly influence mortality in cases of NVE, (OR, 3.19; 95% CI, 0.76-13.38) but significantly improved the prognosis of patients with PVE (OR, 69; 95% CI, 2.89-1647.18).S. aureus endocarditis is an aggressive, often fatal, infection. The results of the current study suggest that valve replacement will improve the outcome of infection, particularly in patients with PVE.

Enterococcal endocarditis on native and prosthetic valves: a review of clinical and prognostic factors with emphasis on hospital-acquired infections as a major determinant of outcome.

Enterococci are the third leading cause of infectious endocarditis, and despite advances in diagnosis and treatment, the mortality of enterococcal endocarditis has not changed in recent decades. Although variables such as advanced age, cardiac failure, and brain emboli have been recognized as risk factors for mortality, cooperative multi-institutional studies have not assessed the role of other variables, such as nosocomial acquisition of infection, the presence of comorbidities, or the changing antimicrobial susceptibility of enterococci, as factors determining prognosis.We conducted the current study to determine the risk factors for mortality in patients with enterococcal endocarditis in a single institution. We reviewed 47 consecutive episodes of enterococcal endocarditis in 44 patients diagnosed according to the modified Duke criteria from a retrospective cohort study of cases of infectious endocarditis. The main outcome measure was inhospital mortality. We applied stepwise logistic regression analysis to identify risk factors for mortality.Predisposing heart conditions were observed in 86.3% of patients, and 17 had prosthetic valve endocarditis. A portal of entry was suspected or determined in 38.2%; the genitourinary tract was the most common source of the infection (29.7%). Comorbidities were present in 52.2% of cases. Twelve episodes (25.5%) were acquired during hospitalization. Only 3 isolates of Enterococcus faecalis were highly resistant to gentamicin. Eighteen patients (40.9%) needed valve replacement due to cardiac failure or relapse. Comparing cases of native valve and prosthetic valve endocarditis, we found no differences regarding complications, the need for surgical treatment, or mortality. Eight of 44 (18%) episodes were fatal. Age over 70 years (p = 0.05), heart failure (odds ratio [OR], 1.61; 95% confidence interval [CI], 1.15-2.25; p = 0.001), presence of 1 or more comorbidities (OR, 3.2; 95% CI, 1.11-9.39; p = 0.02), and nosocomial acquisition (OR, 8.05; 95% CI, 1.50-43.2; p = 0.01) were associated with mortality. In the multivariate analysis, only nosocomial acquisition increased the risk of mortality. In patients with enterococcal endocarditis, nosocomial acquisition of infection is an important factor determining outcome. As the incidence of bacteremia and the population of elderly people at risk continue to grow, the hazard of acquiring nosocomial enterococcal endocarditis may increase; hence, major emphasis must be put on prevention.