Indigenous rapid diagnostic method for Escherichia coli O157:H7.

ABSTRACT

Rapid methods for detection of Escherichia coli O157 H7 diarrhoea are preferred to limit differential diagnostic evaluation including invasive procedures. Fifty stool samples from children and adult patients having diarrhoea and ten control samples from volunteers without diarrhoea were collected. Each sample was inoculated into two tubes containing peptone water and one containing MacConkey broth. They were incubated for 5 hours or longer till growth occurred. The first tube of peptone water with growth was tested for production of indole. All samples were tested for enzyme beta-glucuronidase in the pellet of the second peptone water growth. The MacConkey broth growth was tested with latex beads sensitized separately with antisera to E. coli O157 and E. coli H7. All indole positive and beta glucuronidase negative samples with positive agglutination with E. coli O157 and H7 coated latex beads were taken as E. coli O157 H7 positive samples. Three out of 50 diarrhoeic samples were found to be positive for E. coli O157H7. Confirmation of the results of our rapid assay was done by parallel conventional culture of faecal specimens on sorbitol MacConkey agar. Our rapid assay required only 7-10 hours compared to the conventional technique where the report is available only on the third day. It can therefore be used routinely for initial screening of faecal specimens for E. coli O157 H7.