Streptococcus belongs to the family of lactobacillacae and the majority is facultative anaerobes. The facultative anaerobic streptococci are divided into two categories:
1. those which produce soluble hemolysin and
2. those which do not produce soluble hemolys in The first group of streptococci are called §-hemolytic streptococci, which can be further subdivided into group (a), group (b), group (c) and group (d). It includes most of the species associated with primary streptococcal infections in humans.The group (a) §-hemoIytic streptococci produce various exotoxins such as streptolysin 0 and streptolysin S that can act as antigens. The affected individuals produce specific antibodies against streptolysin 0, namelyAnti-streptolysin 0.Determination of these antibodies is very useful for the diagnosis of streptococcal infections and their relative effects such as rheumatic fever and acute gIomeruIonephritis.An elevated ASO titre of more than 240 IU/ml may indicate an acute streptococcal infection.INSIGHT-ASO detects the presence ofAnti – Streptolysin 0 in human serum, qualitatively, at concentrations as low as 240 IU/ml.