An immunofluorescent method for detecting antibodies against viridans streptococci in Streptococcus viridans endocarditis.

Serum was collected one to three months after the onset of symptoms from eight endocarditis cases and from another endocarditis case about three weeks after the onset of symptoms (case 8 in Table). Endocarditis was proven in each case clinically and by numerous sets of blood -cultures that yielded growth of viridans streptococci. Three positive standard reference sera, obtained from patients with endocarditis, were included with every batch of tests. The first, second, and third reference sera had high fluorescent antibody titres (1 in 1600) against Strep. sanguis, mitior, and mutans respectively. Serum samples were also collected from 20 control cases with carious teeth who were otherwise healthy. A negative control serum was prepared by pooling the