AS-O (Antistreptolysin O)

Immunoturbidimetric method

Product description:

Group A streptococcal (GAS) infections are responsible for 517,000 deaths annually across the world. Once the infection is present within the cells it can cause devastating effects. Streptolysin O (SL-O) is a haemolytic exotoxin that is found in many pathogenic bacteria including GAS. Streptococcus pyogenes produces two distinct haemolysins, termed streptolysins O (oxygen labile) and S (oxygen stable), both of which lyse erythrocytes, polymorphonuclear leucocytes and platelets by forming pores in their cell membrane.

Streptolysin S is responsible for the ?-haemolysis around colonies on blood agar plates. It can also induce the release of lysosomal contents with subsequent cell death after engulfment by phagocytes. In contrast to SL- O, it is not immunogenic due to its small size.

SL-O in patient serum causes lysis of red blood cells (RBCs). This toxin poses highly antigenic effects causing the host to produce the antibody anti-streptolysin O (AS-O). The AS-O test measures the neutralization activity of patient serum for SL-O. All results are measured against a serum standardized by the World Health Organization with a value of 20 000 Todd or international units/mL.Clinically, the presence of these antibodies can indicate a recent GAS infection.