Immunomagnetic-electrochemiluminescent detection of E.coli O157 : H7 in ground beef

An immunomagnetic electrochemiluminescence approach using a commercially av ailable instrument was developed to defect the presence of E. coli O157:H7 in samples of ground beef: The approach can detect E. coli O157:H7 that hav e been incurred with 0.05 CFU of the bacterium per gram of beef after an en richment for 18 h at 37C. Results of comparison tests indicate that the app roach is at least 100 times more sensitive than the Reveal dipstick method with a probable false positive rate less than 4-5%. To enhance the adaptabi lity of the approach, a heat treatment was introduced to eliminate the poss ibility of generating aerosols of live pathogens during the sample loading process. To minimize the carryover of contaminants associated with the capt ure of E. coli O157:H7 by immune magnetic beads (IMB), an immune magnetic s eparation procedure was developed. The procedure involved the use of a magn etic field to first retain the IMB together with captured bacteria on a par amagnetic column. After washing away the contaminants, the target bacteria: were then released from the column by removing the magnetic field. With th e proven sensitivity and improved sample treatment procedures, the ECL appr oach could be considered as an attractive alternative for screening the pre sence of E. coli O157:H7 in foods.