Does primary Streptococcus viridans pneumonia exist?

In 4 adult black patients admitted to an urban general hospital with community-acquired pneumonia, Streptococcus viridans alone was isolated from blood culture (first subculture), in the absence of any other positive microbiological finding. Sputum examination by Gram staining and culture in 3 cases was reported as negative. Echocardiography was performed in 3 cases and was normal, without evidence of endocarditis. The clinical course of illness in the 4 patients is described. The chest radiograph showed a segmental or subsegmental consolidation in all cases; this appeared 'mass-like' in 2 patients. Viridans streptococci may be a more important, if still uncommon, cause of community-acquired pneumonia than previously suspected. The organism should be considered as a possible cause of chest infection, particularly in patients with appropriately positive blood cultures and no other positive microbiological finding.