REAL-TIME REVERSE TRANSCRIPTION PCR DETECTION OF VIABLE SHIGA TOXIN-PRODUCING ESCHERICHIA COLI O157:H7 IN FOOD

Shiga toxin (Stx)-producing Escherichia coli (STEC), particularly E. coli O157:H7, have been associated with food-related outbreaks and have become a global health concern. Detection of low numbers of viable STEC in food is undoubtedly challenging. The present study demonstrated that 7 x 10(2) to 7 x 10(3) cfu E. coli O157:H7 cells in 50 mL of inoculated food samples including apple juice, lettuce and ground beef could be concentrated through a two-step filtration technique. Bacterial RNA was effectively isolated from the concentrated E. coli O157:H7 cells with the combination of Trizol Max Bacterial RNA Isolation Enhancement Reagent and TriReagent (R). Real-time reverse transcription polymerase chain reaction with seven sets of primers targeting virulence and serotype genes of E. coli O157:H7 specifically detected the bacterial RNA representing 1 x 10(2) to 1 x 10(3) cfu viable bactersial cells. The total detection time from sampling to measurement was approximately 4 h. This study provides a rapid and specific detection method for viable STEC in food.