[Detection method of injured Escherichia coli O157 in noodles and vegetables]

An enrichment procedure and a polymerase chain reaction (PCR) method for the detection of injured Escherichia coli O157 in foods were examined. Freeze-injured E. coli O157 inoculated in boiled spaghetti could be detected in 6-h culture within 12 h by the PCR method. Cells injured by heating in boiled spaghetti and cells injured by chlorine treatment in raw lettuce and carrot did not grow sufficiently to be detected in 6-h culture but were detected in 18-h culture using selective agar media. The injured cells could be also detected in 18-h culture within 24 h by the PCR method. Enrichment at 42 degrees C in trypticase soy broth (TSB) was more effective than that at 42 degrees C in modified EC broth with novobiocin. These results indicated that the usage of enrichment in TSB for 18 h at 42 degrees C in combination with the PCR method is suitable for screening for E. coli O157 in boiled or chlorinated foods, even if the O157 cells are injured.