A patient with sore throat has a positive Paul Bunnel test. The causative organism is :

Paul Bunell test is the standard diagnostic procedure of infectious mononucleosis which is caused by EBV. Paul Bunell test detects heterophile antibody. Paul Bunell test In this test inactivated serum (56 0 C for 30 minutes) in doubling dilutions is mixed with equal volumes of a 1% suspension of sheep erythrocytes. An agglutination titre of 100 or above is suggestive of infectious mononucleosis. For confirmation, differential absorption of agglutinins with guineapig kidney and ox red cells is necessary The Paul Bunell antibody develops early during the course of infectious mononucleosis, and disappears within two months. False positive : In patient with lymphoma hepatitis, malaria connective tissue disease Remember : – MC cause of heterophile antibody (+)ve infectious mononucleosis is EBV. – MC cause of heterophile antibody (–) ve infectious mononucleosis is CMV. – Heterophile (–) ve IM also caused by toxoplasmosis, Listeria, non-infectious stimuli.