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

An immunomagnetic electrochemiluminescence approach using a commercially available 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 have been incurred with 0.05 CFU of the bacterium per gram of beef after an enrichment for 18 h at 37C. Results of comparison tests indicate that the approach 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 adaptability of the approach, a heat treatment was introduced to eliminate the possibility of generating aerosols of live pathogens during the sample loading process. To minimize the carryover of contaminants associated with the capture of E. coli O157:H7 by immune magnetic beads (IMB), an immune magnetic separation procedure was developed. The procedure involved the use of a magnetic field to first retain the IMB together with captured bacteria on a paramagnetic column. After washing away the contaminants, the target bacteria: were then released from the column by removing the magnetic field. With the proven sensitivity and improved sample treatment procedures, the ECL approach could be considered as an attractive alternative for screening the presence of E. coli O157:H7 in foods.