Salmonella in foods: new enrichment procedure for TECRA Salmonella Visual Immunoassay using a single rv(R10) only, TT only, or dual rv(R10) and TT selective enrichment broths (AOAC official method 998.09): collaborative study.

A collaborative study was conducted to compare a new enrichment procedure for the TECRA Salmonella Visual Immunoassay (TSVIA) with the reference method given in the U.S. Food and Drug Administration's Bacteriological Analytical Manual (7th Ed.). Three food types (milk powder, pepper, and soy flour) were analyzed in Australia and 3 food types (milk chocolate, dried egg, and raw turkey) were analyzed in the United States. Thirty-eight collaborators participated in the study. The TECRA method was evaluated using both Rappaport-Vassiliadis R10 (RV(R10)) and tetrathionate (TT) broths for selective enrichment. M broth cultures arising from each of the 2 selective enrichment broths were tested in the TSVIA using 2 individual wells, one for each selective broth, and a single well to test the pooled selective enrichment broths. The results for the pooled enrichment broths were reported elsewhere. This study presents the results for the use of single enrichment broths, i.e., RV(R10) only or TT only, with the TSVIA. No significant differences (p > 0.05) were observed for the pairwise comparison of the proportion of positive samples for either RV(R10) or TT used as a single enrichment broth for the TSVIA with that for the reference method.

In-house validation study for salmonella unique testing of juice (modification of AOAC official method 2000.07).

Following an industry request, a study was undertaken to validate a minor change to the Unique method for testing fruit juice. Twenty foods were tested in the original precollaborative study for TECRA Unique Salmonella test (2000.07). To validate the modification for juice, both the modified method (42 degrees C module incubation with a 5 h replication step) and the current AOAC Method 2000.07 (37 degrees C incubation with a 4 h replication step) were compared with the U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM; 8th Ed., 1998) reference method, which uses lactose broth as pre-enrichment medium. Twenty uninoculated replicates, 20 replicates with low-level inoculum (target 1-5 cells/25 g), and 20 replicates with high-level inoculum (target 10-50 cells/25 g) were tested for a single batch of fresh orange juice in accordance with AOAC requirements. There was exact agreement between the 2 Unique methods for all samples and exact agreement between the 2 Unique methods and the BAM method for the uninoculated and high-level inoculum samples. For low-level inoculum, 17 samples were confirmed positive with the new Unique method, 17 with AOAC Method 2000.07, and 14 with the BAM method.