Abstract

Incubation of normal human erythrocytes with the supernatant of centrifuged culture of some strains of Bacteroides fragilis results in the exposure of Tk polyagglutination determinants on the erythrocyte membrane. These determinants are present on non papain-labile structures and are probably exposed by an enzyme mechanism. Other strains of B. fragilis were found to produce neuraminidase, haemolysins, and protease. It is suggested that early recognition of Tk determinants may be an aid to the diagnosis of B. fragilis infection.