Viridans Streptococcal Endocarditis: Clinical, Microbiological, and Echocardiographic Correlations

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Abstract
Infections caused by species within the viridans streptococci have been associated with different clinical characteristics. We studied 36 patients with viridans streptococcal endocarditis. Complications were seen in 10(32%) of 31 patients with native valve endocarditis and four (80%) of five with prosthetic valve endocarditis and included death in two, valve replacement in six, persistent infection in three, emboli in two, and congestive heart failure in nine. Two-dimensional echocardiograms demonstrated vegetations in 26 (72%) of 36, flail mitral valves in seven, disruption of aortic valve prosthesis in one, and perivalvular abscesses in three (two Streptococcus sanguis I and one Streptococcus intermedius I). All twelve patients with native valve endocarditis who suffered complications had vegetations detected by two-dimensional echocardiography, whereas seven patients with native valve endocarditis without vegetations, as detected by two-dimensional echocardiography, had no complications (P = .03). We found no significant correlation between streptococcal species and clinical outcome. To confirm our identifications, we sent 16identical viridans streptococcal endocarditis isolates to five institutions; only three of 16were identified as the same species by all five institutions. We conclude that viridans streptococcal enuor rditis can be associated with a virulent clinical course and that there is marked variability ir species designations of individual strains by different laboratories.