title: Enzyme-linked immunosorbent assay for Pseudomonas aeruginosa exotoxin A.
abstract: An enzyme-linked immunosorbent assay (ELISA) is described for Pseudomonas aeruginosa exotoxin A. A double antibody sandwich method was used, employing polyvinyl microtiter plates as the solid phase, a primary coat of monospecific rabbit antitoxin serum, an outer layer composed of a horseradish peroxidase-sheep antitoxin immunoglobulin G conjugate, and an ortho-phenylene-diamine substrate. Absorbance (optical density) of hydrolyzed end product was read spectrophotometrically at 492 nm. ELISA detected as little as 30 pg (0.3 ng/ml) of purified toxin, and absorbance was linear over a 20-fold or greater concentration range. Toxin was demonstrated in culture filtrates from 42 of 48 (88%) consecutive clinical P. aeruginosa isolates compared with 37 of 48 (77%) positive by hemagglutination inhibition. Results of the two assays correlated closely (r = 0.82, P less than 0.001). Specificity was confirmed by neutralizability of ELISA activity with monospecific antitoxin. ELISA was thus a sensitive, specific, and quantifiable technique for the assay of P. aeruginosa exotoxin A in both purified and crude culture materials.
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D005098:Exotoxins / Q000032:analysis*; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007124:Immunoenzyme Techniques; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000032:analysis*
chemical_list: D005098:Exotoxins