RAPID FLUORESCENCE CONCENTRATION IMMUNOASSAY FOR DETECTION OF SALMONELLAE IN CHICKEN SKIN RINSE WATER

Salmonellae in chicken carcass rinse water or enrichment broth were de tected with a fluorescence concentration immunoassay (FCIA) using inta ct salmonellae cells as the reacting particles. Sample solutions and r eagents were added to a 96-well fluoricon assay plate and incubated 30 min in the chamber of a fluorescence concentration analyzer at room t emperature. The bound and free components were separated by automated vacuum filtration and washings through the membrane filters equipped a t the bases of the wells. The fluorescent signals were concentrated th rough vacuum filtration and were read at a wavelength of 485/535 nm. A cut-off value of the arbitrary fluorescence units was calculated by a dding. two standard deviations to the mean value of the negative contr ol. When the arbitrary fluorescence units of a sample were above the c ut-off value, it was scored positive indicating the presence of salmon ellae in the test suspensions. It was found the FCIA method could dete ct salmonellae at 1.25 x 10(4) cells per ml in pure culture and was sp ecific enough to screen salmonellae from four types of common chicken carcass contaminating bacteria. By coupling with 18-h direct enrichmen t in selenite cystine broth of the whole carcass rinse, the detection of salmonellae in chicken carcass rinse water was accomplished in less than 24 h.