Bacteriology and

Several publications have demonstrated the increased frequency of enterococcus and other streptococci of group D (e.g, S. bovis) in causing bacterial endocarditis in the elderly. In the publication of Selton-Suty et al. [11] older patients (> 70 years) with infective endocarditis had a significantly higher percentage of group D streptococci and enterococci compared to the younger patients (<70 years) [10 patients (47.6%) versus 15 patients (19.5%), P < 0.04]. A recent publication [17] also demonstrated that among 1,285 patients with left-sided native valve endocarditis, 107 (8.3%) had enterococcal endocarditis most frequently seen in elderly men, frequently involving the aortic valve, tending to produce heart failure rather than embolic events and associated with relatively low short-term mortality. Compared to patients with streptococcal endocarditis, those with enterococcal endocarditis were more likely to be nosocomially acquired (15% vs. 1%; P < 0.0001) and have heart failure (46% vs. 35%; P = 0.03). Compared to patients with S. aureus endocarditis, patients with enterococcal endocarditis were less likely to embolize (26% vs. 49%; P < 0.0001) and less likely to die (11% vs. 27%; P = 0.001). Multivariable analysis showed that enterococcal endocarditis was associated with lower mortality than other etiologies in patients with left-sided endocarditis (odds ratio [OR] 0.49; 95% CI 0.24-0.97). As far as culture-negative endocarditis is concerned, there was no significant difference in the number of culture negative endocarditis between the older and younger patients.

Di Salvo et al. [18] studied 315 consecutive patients with definite infectious endocarditis. Patients were separated into three groups: group A included 117 patients aged < 50 years, group B included 111 patients aged > 50 and < 70 years and group C included 87 patients aged > 70 years. A digestive presumed port of entry was more commonly detected in group C (19%)

and in group B (16%) than in the younger patients (5%), P < 0.0001. Similarly, the urinary tract as the presumed port of entry was more frequent in group C (13%) than in the other groups (group A = 2% and group B = 6%, P < 0.005). The presumed port of entry was supported by the distribution and etiology of the pathogens. The most frequent isolated pathogens were Streptococci found in 45% of patients. The proportion of S. bovis endocarditis was higher in groups B and C than in group A [25 (22%), 14 (16%) and 6 (5%), respectively, P <0.001]. The proportion of enterococci was highest in group C [5 (5%) in group A, 5 (4%) in group B and 8 (9%) in group C] while S. aureus was more frequent in younger patients [34 (29%) in group A, 19 (17%) in group B and 15 (17%) in group C]. Thus, the bacteriological features of endocarditis in the elderly reflect the common sources of bacteremia relating to the co-morbidities typical of this age group. S. bovis probably relates to colonic lesions and enterococci relates to urogenital infections.

The high incidence of S. bovis endocarditis in the elderly as well as the difficult clinical course related to this pathogen is also evident when studying the clinical course of these infections compared to other pathogens. Pergola et al. [19] studied the clinical, echographic and prognostic features of S. bovis endocarditis compared to endocarditis caused by other streptococci and "other pathogens" in a large sample of patients. Two hundred six patients with a mean age of 57 (SD 15) years with a diagnosis of infective endocarditis formed the study population. S. bovis endocarditis was documented in 40 patients, other Streptococci were identified in 54 and "other pathogens" were documented in 112 patients. The mean age was 64 (SD 12) years in the S. bovis group, 55 (SD 15) years in the other Streptococci group and 56 (SD 16) years in the "other pathogens" group, P < 0.05. Multiple valve involvement, native valves and large vegetations (>10 mm) were more frequent in patients with S. bovis. There was a significantly higher rate of embolism in the S. bovis group. Splenic infarcts and multiple embolisms were significantly more frequent in patients with S. bovis. Gastrointestinal lesions, anemia and spondylitis were also observed more frequently with S. bovis endocarditis. The relationship between age and prevalence of S. bovis endocarditis is depicted in Figure 3.2 [20].

Mean age (years)

Figure 3.2. Microbial epidemiology of infective endocarditis. Linear regressions between proportion of S. bovis disease and mean age [20].

Mean age (years)

Figure 3.2. Microbial epidemiology of infective endocarditis. Linear regressions between proportion of S. bovis disease and mean age [20].

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