IMMUNOBLOTTING IN THE DIAGNOSIS OF CULTURE-NEGATIVE ENDOCARDITIS CAUSED BY STREPTOCOCCI AND ENTEROCOCCI

Aim-To improve the diagnosis of culture negative endocarditis by diagn osing cases due to streptococci and enterococci. Method-Serum samples were immunoblotted against extracts of the commonest streptococci and enterococci. They were selected from patients with a cardiac murmur, p ersistent pyrexia and at least three negative blood cultures. The pres ence of patterns of endocarditis species specific antigenic bands was measured and correlated with clinical outcome. Results-Negative serolo gy was found in 28 patients where the diagnosis of endocarditis was re jected or, if proved, staphylococcal, yeast, Gram negative, systemic l upus erythematosus, due to Q fever or Chlamydia psittaci or nonbacteri al thrombotic. Positive serology was found in 27 of the 34 patients wh ere the response to antibiotics suggested streptococcal or enterococca l infection. In 22 of these there was objective evidence of endocardit is. Positive serology was also found in three of four further patients with vegetations at necropsy. Conclusion-The identification of patter ns of antibody response on immunoblotting can be used to make a specif ic diagnosis of streptococcal or enterococcal endocarditis in the abse nce of positive blood cultures.