Detection of freeze-injured Escherichia coli O157 : H7 cells from foods byresuscitation prior to selective enrichment

We tried to detect Escherichia coli O157:H7 in food samples artificially co ntaminated with freeze-injured E. coli O157:H7 using, an enrichment method with modified EC broth supplemented with novobiocin (mEC + n). When the sam ples were cultured for enrichment immediately after inoculation of freeze-i njured cells, E. coli O157:H7 was not detected in 13 out of 18 samples. How ever, allowing the food samples to stand for 3 h at room temperature prior to enrichment in mEC + n remarkably improved recovery of E. coli O157:H7 ex cept for some acidic foods. E. coli O157:H7 was detected in the acidic food s by introducing a resuscitation step of 3-h of incubation in a non-selecti ve broth at room temperature prior to enrichment with mEC + n. (C) 2000 Els evier Science B.V. All rights reserved.