Comparative evaluation of labelling intensity for detection of enterotoxigenic Escherichia coli

Twenty four Esch. coli isolates obtained from patients of diarrhoea were tested by DNA hybridization for presence of enterotoxigenic Esch. coli (ETEC). The probe generated for this study was labelled by two different ways using the large Klenow fragment of DNA polymerase-I. It was observed that labelling by sequential harnessing of the exonuclease and polymerase activity of the enzyme was superior to extension of random hexanucleotide primers. This method besides being economic, dispenses with the critical step involved in the thermodynamics of oligoannealing and initiation of DNA synthesis.