Species specific PCR based detection of Escherichia coli from Indian foods

Escherichia coli is a faecal indicator and certain virotypes are known as pathogens. Therefore, detection and prevention of E. coli in food is very important. The existing rapid methods concentrate on detecting the pathogenic E. coli instead of total E. coli population. Present study evaluates the use of two molecular markers (uidA and flanking region of uspA) specific for the E. coli in combination with microbiological method for confirmation. Majority of the isolates (77%) were positive for both the genes tested. However, 22% of the E. coli isolates were positive for any one of the two primer sets [uidA (9%) and flanking region of uspA (13%)]. High levels of E. coli incidences (92% samples) were observed in beef while low occurrence (19% samples) was found in sprouts. Low percentage (7.3%) of E. coli isolates was positive for virulence genes tested (lt, ipaH, aggR, eaeA, stx1 and stx2). Two isolates were positive for stx genes. However, none of the isolates including stx positive isolates were E. coli 0157:H7. Maximum number of the E. coli (44%) isolates was characterized under phylogenetic group B2. This phylogenetic group comprises of extra intestinal and virulent E. coli strains.