The use of a rapid Salmonella latex serogrouping test (Spectate(R)) to assist in the confirmation of ELISA-based rapid Salmonella screening tests

Spectate (R), a 10 min, simple, lates-based agglutination test for serogrouping of salmonellae, has been investigated as a tool to assist in the confirmation of ELISA presumptive positive broth samples when screening for salmonellae in foods. When obtaining a combined ELISA and Spectate positive result, there was a 90% (27/30) confidence limit of a genuine positive result, some one or two working days quicker than the traditional methods. Of the 10% (3/30) that were not confirmed as salmonellas, two gave a Spectate result which is advised as being a possible Citrobacter spp. and one sample gave a positive confirmation by Spectate only, which suggested a failure of the traditional confirmation process, a finding confirmed at other sites. Extensive studies performed at several food company microbiology laboratories showed Spectate to be a useful additional tool in the confirmation process of ELISA screening techniques for salmonellae in food. Additionally the concept of a 'false positive' may need to be refined to that of a 'not culturally' positive, given the apparent possible failure of the traditional confirmation methods.