Detection of Escherichia coli O157:H7 bacteria by a combination of immunofluorescent staining and capillary electrophoresis

As the number of incidents of bacterial infections continues to rise around the globe, simpler, faster, and more sensitive diagnostic techniques are required to improve the safety of the food supply and to screen for potential bacterial infections in humans. We present here direct and indirect approaches for the detection of bacteria, which are based upon a combination of immunofluorescent staining and capillary electrophoresis. In the direct approach, Escherichia coli O157:H7 bacteria stained with fluorescein-tagged specific antibodies are detected by CE, while in the indirect approach fluorescein-tagged specific antibodies to E. coli are first captured by E. coli O157:H7 bacteria and then released and detected by CE. We have identified suitable bacteria staining and CE protocols, which involved a 10 mM Tris-borate-EDTA (TBE) buffer, 0.25 μg antibody/1 million bacteria, and capillaries dynamically coated with poly-N-hydroxyethyl-acrylamide (polyDuramide). We have also successfully detected the presence of E. coli O157:H7 in contaminated meat. The total time required for analysis was 6-8 h, which is less than that realized in most commercial assays presently available.