Bacteriological detection of Salmonella in the presenceof competitive micro-organisms

A fifth bacteriological collaborative study organised by the Community Reference Laboratory for Salmonella had as participants the National Reference Laboratories for Salmonella (NRLs-Salmonella) of the EU Member States. The objectives were: 1) To evaluate the results of the detection of different contamination levels of Salmonella Enteritidis (100 and 500 cfp) and Salmonella Typhimurium (10 and 100 cfp) in the presence of competitive micro-organisms among and within the NRLs-Salmonella, and 2) To evaluate MSRV as selective enrichment medium compared to RV, used as the selective enrichment medium in the standard method. An adapted ISO 6579 (proposed reference) method was used in combination with MSRV and, optionally, the laboratory's own routine method for the detection of Salmonella in chicken faeces. Significantly more positive isolations were obtained with the STM100 capsules than with the STM10, SE100 and SE500 capsules. The number of positive isolations from the SE100 capsules was also significantly lower than the number of positive isolations from the STM10 and SE500 capsules. Significantly more positive isolations were obtained using MSRV compared to using RV. Significant differences were also found between laboratories. When compared with RV, the use of MSRV led to significantly more positive isolations from the naturally contaminated samples containing S. Enteritidis.