Poster 177.  Congresso da Sociedade Brasileira de Toxinologia, 8., Symposium of the Pan American Section of the International Society on Toxinology, 8., 2004, Angra dos Reis, Brasil.  Abstracts...  J. Venom. Anim. Toxins incl.Trop. Dis., 2004, 10, 3, p.536.

 

 

Development of a rapid test for the detection of staphylococcal enterotoxins in foods

 

1Campos, P.C.; 2Carmo L.S.; 3Linardi V.R. and 1Heneine, L.G.D.

 

1 Laboratory of Immunology and Bioproducts, DP, FundaçãoEzequiel Dias, Belo Horizonte, 2 Laboratory of Enterotoxins, IOM, Fundação Ezequiel Dias, Belo Horizonte, 3 Department of Microbiology, UFMG, Belo Horizonte.

 

Contamination of foods and food products by staphylococcal enterotoxins are still a major cause of concern to health services and industry. For this study four enterotoxins, (SEA, SEB, SEC, and SED) were purified and used to raise antibodies in sheep. Later the antibodies were adsorbed onto toxin affinity columns to render each one specific for the homologous toxin. Conjugates, HRP-specific antibody were individually prepared and together with the purified toxins and non-conjugated specific antibodies used to set up an ELISA. The in-house ELISA was compared to a commercial kit showing similar sensitivity and specificity for the food samples tested. The results permitted us to persue the rapid test. For the rapid test two conjugates were prepared, the HRP and a coloidal-dye antibody conjugate. Both tests were direct antibody- sandwich based and the support matrix was nitrocellulose. Affinity purified antibody for SEA was coated onto nitrocellulose strips and incubated overnight at 4º C. After a washing and blocking step, samples were added and later developed with either conjugate. Control curves were prepared using known amounts of SEA diluted in 0,1 M PBS pH 7,2 and in non-contaminated food extracts. For the coloidal-dye conjugate, sensitivity was 300ng/ml of toxin. For the HRP-conjugate sensitivity was of 15 ng/ml. This later test was compared to the VIDAS test (Biomerieux) with food samples collected from restaurants with an average count of 105 UFC/g of Staphylococcus sp and only in one sample SEA was detected in both tests. The HPR-conjugate test is being pre-validated according to NIH procedures and the preliminary results indicate that it could be used for the screening and diagnostic of contaminated foods with staphylococcal enterotoxins.

 

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