Final answer:
To detect antibodies against bacteria in an EIA, an enzyme-linked immunosorbent assay (ELISA) is performed by attaching bacterial antigens to a microtiter plate, and the presence of specific antibodies is indicated by a measurable color change.
Step-by-step explanation:
To detect antibodies against bacteria in the bloodstream using an EIA, we would run a enzyme-linked immunosorbent assay (ELISA), which we would start by attaching the antigen from the bacteria to the wells of a microtiter plate. In this process, the antigen is first attached to the wells to capture specific antibodies from a test sample. If antibodies are present in the sample, they will bind to the immobilized antigens.
Following this, an enzyme-linked secondary antibody specific for human antibodies is added, which binds to any bound primary antibodies. After washing away unattached materials, a substrate for the enzyme is added, resulting in a color change that indicates the presence of the antibodies. The intensity of this color change is measured using a spectrophotometer and is proportional to the amount of specific antibody in the sample.