Escherichia coli as a biologically active ingredient of suppositories. Solid phase extraction and quantification in a double antibody ELISA.

Techniques for isolation and quantification of an active ingredient of biological origin from a pharmaceutical product (Posterisan suppositories) were developed. By means of ELISA (enzyme-linked immunosorbent assay) in connection with a computerized evaluation, the antigenic material, a bacterial culture suspension (BCS) of Escherichia coli as a raw material was shown to be specifically and reproducibly detectable and quantifiable. As a limit of detection, a bacteria concentration of 6 x 10(4) cells/ml was determined, corresponding to 0.02% of the concentration in the product. After treating of the suppositories with organic solvents, the E. coli antigens were extracted with silica columns. The complete validations of both methods, the ELISA itself and the extraction procedure of the antigens from the matrix, in accordance with pharmaceutically accepted principles are presented. The eventual application of the new technique to the analysis of other pharmaceuticals with similar ingredients as well as the possibility of substituting conventional methods like total cell counting is discussed.