Clinical significance of titered circulating microbial antibody in bacteremia

Using an indirect immunofluorescent antibody technic, the authors determined the serum microbial antibody titer (MAT) in 26 patients (five with infective endocarditis, eight with septicemia without endocarditis, and three with access device-related bacteremia, three with fungemia without endocarditis, and seven with false-positive blood cultures). The MAT in the early clinical stage of infective endocarditis (IE) exceeded 350; after appropriate antibiotic therapy, it decreased to below 50 with clinical improvement. MAT in patients with septicemia was above 20 and less than 200; in patients with bacteremia, above 10 and less than 50; and in patients with false-positive blood cultures, it was less than 10. The authors suggest that MAT against isolated bacteria may be useful in diagnosing septicemia with or without IE, in determining the appropriate length of treatment, and in differentiating bacteremia from false-positive blood cultures.