Evaluation of a new latex agglutination test for detection of streptolysin O antibodies

Abstract

Acuteand convalescent-phase serum specimens were collected from 50 patients with group A streptococcal pharyngitis. The anti-streptolysin O (ASO) titer for each serum specimen was determined by using both the standard neutralization assay and the latex agglutination (LA) test (Rheumagen ASO; Biokit Inc., New Britain, Conn.). When the ASO titers derived by the two methods were compared, the correlation coefficient was 0.93. When the ability of the LA test to demonstrate a significant ASO titer rise (.2 dilutions) was compared with that of the standard neutralization assay, the LA test had a sensitivity of 91%, a specificity of 86%, a positive predictive value of 83%, and a negative predictive value of 92%. Triplicate LA test determinations were performed on a subset of 31 serum specimens, and for 29 (94%), the repeated ASO titers were all within 1 dilution of each other; the width of the 95% confidence interval for the triplicate measurements of each serum specimen was ±32.8 IU. We found the Rheumagen ASO to be a simple, rapid LA procedure for measuring ASO titers that produces results that are highly reproducible, show little lot-to-lot variability, and are comparable to the ASO titers obtained with the standard neutralization assay.

Cloning and expression of a surface immunogenic protein in Streptococcus dysgalactiae isolated from fish and its application in enzyme‐linked immunosorbent assays to diagnose S. dysgalactiae infections in fish

“…Similarly, streptolysin O, a toxic protein produced by Streptococcus pyogenes, induces a strong immune response in the infected host (Strollerman et al 1965). Titres of anti-streptolysin O antibody have been used for diagnosing S. pyogenes infection in humans (Gerber, Caparas & Randolph 1990). Hence, if an immunogenic protein inducing an antibody is identified in fish infected with GCSD, both a sero-diagnostic method to detect the infection and a vaccine against this infectious disease can be developed.…”