Infective endocarditis. A review of selected topics

Clinical evaluation of a fluorescent antibody test for the serological diagnosis of streptococcal endocarditis

Serum fluorescent streptococcal antibody tests were carried out on 71 patients with clinically suspected infective endocarditis, and a final diagnosis of endocarditis was obtained in 46 patients. A serological diagnosis of streptococcal endocarditis was obtained in 10 patients who had persistently negative blood cultures, as fluorescent streptococcal antibody titres equal to or greater than 400 were detected against at least one of four strains of streptococci used as heterologous antigens. There were no false positive fluorescent antibody results with heterologous antigens during tests on 29 patients who had either non-streptococcal endocarditis, a final diagnosis other than endocarditis, or streptococcal sepsis not associated with endocarditis. A negative result with the heterologous antibody test could not, however, exclude a diagnosis of streptococcal endocarditis as six of 11 patients with endocarditis due to Streptococcus viridans or Str bovis confirmed on blood culture had serum fluorescent antibody titres less than 400 against all the heterologous streptococcal antigens tested. Homologous fluorescent streptococcal antibody titres equal to or greater than 400, using the patient's own blood culture isolate as the antigen, were found in the serum samples of 14 of 15 patients with endocarditis caused by viridans streptococci, three patients with enterococcal endocarditis, two patients with endocarditis caused by Str pneumoniae, and one patient with Str bovis endocarditis. In contrast, all five patients who had clinically insignificant streptococcal bacteraemias had serum fluorescent homologous antibody titres of only 100 or less. These results showed that the homologous serum fluorescent streptococcal antibody test could help to decide the clinical importance of a streptococcus which is initially isolated from only one or two of a number of inoculated blood culture bottles.

A comparative study of 48 host valve and 24 prosthetic valve endocarditis cases

Forty-eight cases of host valve endocarditis and 24 cases of prosthetic valve endocarditis occurring during a concurrent period of time were analyzed to assess differences between the two groups. The over-all incidence of prosthetic valve endocarditis during this 40 month period was 4.4%. The symptoms and signs in both groups were similar, except that PVE patients had more frequent occurrences of changing heart murmurs and splenic and cerebral emboli. Spleen scans may be helpful in the diagnosis of selected cases of culture-negative prosthetic valve endocarditis. There was no significant difference between the two groups for the various infecting microorganisms. However, the culture-negative prosthetic valve group had a mortality rate of 77.7% compared to 46.2% for the host valve group. In the HVE patients the oral cavity or urinary tract was the probable source of infection in 50.0% of the patients. In about one third of HVE cases, there was strong evidence that the infection was related to a therapeutic procedure, whereas nearly half of the PVE patients had clinical evidence of an extracardiac infection at the time of open-heart surgery. We emphasize the need for good pre- and postoperative surveillance to eliminate possible predisposing infections and appropriate antibiotic prophylaxis in all patients with valvular disease at times of risk. The survival rate in patients with prosthetic valve endocarditis was highest in those patients who received "appropriate" antibiotics and, if significant congestive heart failure was present, surgical intervention was necessary.