Development and application of immunochromatographic tests for the detection of staphylococcal enterotoxin E

Two rapid immunochromatographic assay formats for the detection of Staphylococcus aureus enterotoxin serotype E (SEE) were developed. For both tests, polyclonal antibodies against SEE were immobilized on a membrane strip representing the test zone, while second anti‐SEE antibodies conjugated to dyed latex particles were employed as markers in sandwich immunoassay. In a two‐step test format, sample and labelled antibodies were preincubated prior to immunochromatography, whereas in a one‐step test the labelled antibodies were integrated in the test pad and activated by addition of the sample solution. In the presence of SEE in a sample solution, colour development at the antibody‐coated zone occured within 20 min. The visual detection limits for SEE in buffer solution were at 5 ng ml^?1 (two‐step test) and at 10 ng ml^?1 (one‐step test), respectively. Both assays were specific for SEE and showed no cross‐reaction with serotype A, B, C, and D enterotoxins. When the two‐step test format was used for the identification of SEE in S. aureus culture broth, the detection limit was found to be 10 ng ml^?1. Culture supernatants of 10 enterotoxigenic strains of S. aureus were analysed with the immunochromatographic two‐step test and with a microtitre plate enzyme immunoassay (EIA) test kit for enterotoxins A‐E. Results obtained by the immunochromatographic test (presence or absence of SEE) were in excellent agreement with those of the microtitre EIA.