Screening of Escherichia coli in vegetable samples marketed in different districts of Istanbul in consideration of occurence of Shiga-like toxin genes by real-time PCR assay

In this study the presence of Escherichia (E.) coli in some selected vegetable samples such as carrot, cucumber, tomato, lettuce, parsley and spinach were studied in consideration of occurence of Shiga-like toxin genes by Real-Time PCR. 30 samples from each of the vegetables, totally making 180 were collected in different districts of İstanbul. The samples were initially investigated for E. coli by culture-based microbiology. Those with a positive E. coli occurence were also examined for stx1, stx2 and eae genes according to two different methods by Real-Time PCR assay. DNA isolations were made by following up the instructions in Eurofins GeneSpin DNA Isolation Kit and by diluting the colonies. The obtained results by culture-based microbiology showed that occurrence of E. coli in the samples was found as 93.3% in spinach; 93.3% in lettuce; 86.6% in parsley; 43.3% in carrot; 33.3% in cucumber and 13.3% in tomato. On the other hand, screening by Real-Time PCR was also performed for these positively contaminated samples in order to understand serotype of E. coli by stx1, stx2 and eae genes. The Real-Time PCR study resulted in STEC O157:H7 in carrot and lettuce; STEC O26:H11 and STEC O111:NM in carrot; STEC O119:H16 in carrot, lettuce, cucumber and parsley; STEC O157:NM in lettuce and EPEC O119, EPEC O111:H2, EPEC O26:NM in carrot, cucumber, tomato, lettuce, parsley and spinach, respectively.In conclusion, it was shown that vegetable samples marketed in different districts of İstanbul were positively contaminated by E. coli according to the culture based microbiology. The results were also validated by Real Time PCR and pathogen stx1, stx2 and eae genes significantly harmful to the public health were detected by Real-Time PCR assay