Enzyme linked immunosorbent assay (ELISA)
Enzyme linked immunosorbent assay was performed using a commercially
available sandwich ELISA kit for E. coli HCP testing from Cygnus
Technologies (Southport, NC). Both the standard included in the kit (kit
standard) and an E. coli cell lysate supernatant were used to
calibrate the amount of residual E. coli HCPs in the final API
samples. In addition, the immunoreactivity of several other enzymes used
in the reaction was also tested by the commercial kit to determine if
the kit antibody recognizes those enzymes.