Serum antibodies to a Staphylococcus aureus thermonuclease preparation in healthy persons and patients with bacteremia

Abstract

An enzyme-linked immunosorbent assay (ELISA) was used to measure antibodies against a commercial nuclease preparation from Staphylococcus aureus. The preparation contained at least five proteins, including the 17 kD thermostable nuclease (TN). Paired serum specimens from patients ( n=26) with bacteremia caused by S. aureus and single specimens from patients ( n=19) with bacteremia caused by various other bacteria, were diluted 1 2000 and tested for IgG antibodies against the TN preparation. The cut-off level for positive test was defined as mean plus 2.5 SD of the antibody levels found in blood donor sera ( n=50). Of the patients infected with S. aureus, 16 26 (61·5%) showed positive TN ELISA with the first serum sample and 23 26 (88·5%) with the second serum sample, versus 2 19 (10·8%) of those bacteremic with other bacteria, and 1 50 (2%) of the blood donors. Of 30 sera from patients with S. aureus bacteremia tested for comparison, 22 30 (73·3%) showed a positive TN ELISA and 8 30 (22·6%) a positive Latex agglutination test for anti-staphylolysin antibodies. Western blot analysis showed that patients infected with S. aureus produced antibodies against the proteins with molecular weights of 35, 17 (TN), and < 10 kD, respectively. The TN ELISA may be an alternative to established serological tests for the diagnosis of serious S. aureus infections.