Escherichia coli O157:H7 Contamination Rates Using Chromogenic Medium in Selected Foods Consumed at some Restaurants in Tehran

Eschirichia coli are considered as a contamination indicator of water and foods to coliform pathogens. Some E. coli serotypes such as E. coli O157:H7 cause serious complications such as hemorrhagic colitis and hemolytic uremia syndrome. The main objective of this study was to the determination of E. coli O157:H7 contamination rates using chromogenic medium in some selected foods consumed at some restaurants in Tehran. A total of 96 food samples, including 48 salads and 48 crushed kebabs were randomly collected from four restaurants in Tehran. Using sterile collection equipment, 12 samples from each restaurant were collected two times with two month interval. Standard biochemical and bacteriological methods and chromogenic medium were used for the detection of E. coli and E. coli serotype O157:H7. The results of this study showed that out of 96 tested samples, contamination to E. coli in 29 samples (30/2%) was confirmed in which 17 samples were contaminated to E. coli O157 however no E. coli O157:H7 strains were detected when all positive E. coli O157 isolates were subjected to serotyping. The results of this study showed that the hygienic quality of ready-to-use salads and foods consumed in the restaurants under study was not ideal; therefore the implementation of more surveillance and supervision on those restaurants is recommended.