Coagglutination is a rapid slide agglutination technique used to detect bacterial antigens, for example in CSF for meningitis. The carrier particle used in coagglutination is:

• A Latex beads coated with F(ab')2 fragments
• B Staphylococcus aureus rich in protein A, with specific antibody bound to it ✓
• C Formalinised sheep red blood cells coated with antigen
• D Colloidal gold particles conjugated to enzyme

Explanation

Coagglutination uses killed Staphylococcus aureus Cowan strain I, whose surface protein A binds the Fc portion of IgG molecules. Specific IgG is adsorbed onto the bacteria leaving Fab regions free, so when homologous soluble antigen is present the antibody-coated staphylococci agglutinate visibly. Latex beads are the carriers in latex agglutination, a separate technique, and formalinised red cells are carriers in passive haemagglutination. Colloidal gold conjugated to enzyme describes immunochromatographic labels, not coagglutination.

Reference: Ananthanarayan and Paniker Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.