Rapid assay for pathogenic salmonella organisms by immunofluorescence flow cytometry

Abstract

Summary Multi‐parameter flow cytometry was investigated for the rapid detection of specific serotypes of salmonellas (S. typhimurium and S. montevideo) labelled with fluorescent monoclonal antibodies, both in pure culture and in a typical food matrix (full‐fat milk). In all cases, the method was accurate to levels of below 104 target cells per ml for a total assay time of about 30 min. After 6 h non‐selective enrichment in the presence of a 10 000‐fold excess of competing micro‐organisms (Escherichia coli) the corresponding detection limit was about 20 cells ml−1. These results suggest that flow cytometry has significant potential for the detection of pathogenic micro‐organisms in the food industry.

Improved detection of bacteria by flow cytometry using a combination of antibody and viability markers

“…The present authors have previously reported immunofluorescent labelling techniques which allow the detection of two species of salmonellas simultaneously, down to levels of 1×10 3 ml −1 in pure cultures (McClelland and Pinder 1994a), and 1×10 3 and 1×10 4 cells ml −1 in milk and egg, respectively (McClelland and Pinder 1994b ;Pinder and McClelland 1994). The total analysis time in all these cases was about 30 min.…”

Detection of low levels of specific Salmonella species by fluorescent antibodies and flow cytometry

“…This study shows that the FCM method for the multiparameter detection of salmonellas in food should be possible as far as sensitivity and rapidity is concerned. Preliminary results on food show that this is possible (Pinder and McClelland 1994).…”

A Flow Cytometry Method for Rapid Detection and Enumeration of Total Bacteria in Milk

“…For example, immunofluorescent labeling techniques have been used to detect Listeria monocytogenes (9) in raw milk and specific Salmonella spp. in raw and processed milks (4,16,17,19). In additional studies, we have found that FCM is suitable for monitoring the growth of bacteria in refrigerated raw, pasteurized, homogenized milk and flavored milk drinks and enumerating viable bacteria (2; T. Gunasekera et al, unpublished results).…”