ANTIBODY-RESPONSE IN 6 HACEK ENDOCARDITIS CASES UNDER THERAPY

The antibody response to bacteria of the so-called HACEK group, i.e. H aemmophilus spp., Actinobacillus actinomycetemcomitans, Cardiobacteriu m hominis, Eikenella corrodens and Kingella kingae, was measured in se ra of six patients with endocarditis. The corresponding isolates from their blood cultures were identified by conventional methods, includin g reactions for nitrate reduction and catalase as well as acid product ion from sugars. Crude antigens were prepared by glycine extraction an d sonification of the blood culture isolates, and used to determine ti ters by complement fixation. A patient with Haemophilus parainfluenzae bacteremia received a short course of antibiotic therapy, and relapse d with spondylitis and endocarditis 5 months later. Titers of sera aga inst his own isolate rose from 1:40 to 1:320 and fell to 1:40 after th erapy within one year. A patient with C. hominis endocarditis had a si milarly prolonged course. The complement fixation titer against his ow n isolate was already 1:240 before antibiotics were administered. Anot her patient with C. hominis endocarditis presented a titer of 1:320 2 weeks after the diagnosis. These three patients revealed C-reactive pr otein values over 50 mg/l in the first serum sample. Decrease of both antibody titers and C-reactive protein values correlated with clinical improvement. Two patients with prosthetic valve replacement 5 months earlier developed C. hominis and K. kingae endocarditis, respectively. At admission, C-reactive protein values were 64 and 82, respectively, and therapy was instituted immediately. The first sera were received 3 and 6 weeks, respectively, after isolation of the corresponding bloo d culture isolates and revealed already low titers, i.e. 1:80 and 1:60 , respectively. A woman with A. actinomycetemcomitans endocarditis rec eived immediate therapy and did not develop titers against her own iso late. CRP was 100 at admission and remained over 50 5 weeks later. We conclude that the complement fixation assay with individual antigen pr eparations was easy to perform and allowed monitoring of the antibody response in 5 of 6 HACEK endocarditis cases under therapy, but the use fulness of this method to find culture-negative HACEK endocarditis nee ds to be established.