Verocytopathic activity of Escherichia coli O157 & other 'O' serogroups isolated from patients of diarrhoea.

Twenty diarrhoeal isolates identified as Esch. coli O157 were screened for cytopathic activity on the continuous Vero cell line. Of these, seven strains (35%) showed cytopathic effect which was maximum on the 4th day after inoculation, with a maximum titre of 1 in 128. The total loss of cytopathic activity was observed in the positive filtrates subjected to a temperature of 100 degrees C for 15 min, while heating at 65 degrees C for 15 min, resulted in partial loss of this activity. All the verocytopathic strains were obtained from infants and children and were devoid of heat labile (LT) and heat stable (ST) toxins as well as enteroinvasive property.