DETECTION OF SALMONELLA IN FOODS BY IMMUNOMAGNETIC SEPARATION

Immunomagnetic separation (IMS) was used for the detection of Salmonel la spp. in poultry, raw egg products, spices and minced meat in parall el with the traditional cultural method (ISO 6579, 1990), as a referen ce method. The IMS was employed to replace selective enrichment in liq uid media i.e. Rappaport-Vassiliadis magnesium chloride malachite gree n (RV) and selenite cystine (SC) broth so that a direct transfer of im munomagnetically separated salmonellae from the preenrichment medium t o selective plating media was possible. Of 165 naturally contaminated food samples tested 54 (32.7 %) were found to harbour salmonellae usin g both IMS and the cultural method. Similar results were obtained with either method with 43 artificially contaminated food samples (10 cfu Salmonella per 25 g sample) tested. The levels of Salmonella contamina tion in positive food samples were estimated by the application of thr ee tube most probable number (MPN) technique using replicates of 10.0 g, 1.0 g, and 0.1 g samples. In the present study, IMS seems to be a s imple, rapid and equally efficient method to enrich Salmonella selecti vely from a pre-enrichment as compared to the traditional cultural met hod.