Preliminary evaluation of flow-through immunocapture followed by real-time PCR for the detection of Salmonella serovars on tomato surfaces within 8 hours.

This study reports a preliminary evaluation of flow-through immunocapture (FTI) followed by real-time PCR (FTI-PCR) for the detection of Salmonella serovars on tomato surfaces within 8 h. The FTI-PCR method was compared with real-time PCR, direct plating of FTI beads on xylose lysine desoxycholate (XLD), and the conventional culture method for Salmonella found in the U.S. Food and Drug Administration's (FDA) Bacteriological Analytical Manual (BAM). Unwaxed green tomatoes were spot inoculated with a five-serovar Salmonella cocktail on smooth surfaces at levels of 10(0) to 10(4) CFU per tomato and washed in lactose broth (LB) using a shake-rub method. The resulting LB rinse was incubated at 37 degrees C for 4 h prior to analysis by FTI-XLD, real-time PCR, or FTI-PCR and for 24 h as the first step in the BAM Salmonella culture method. For FTI-XLD, the observed lowest detection level (LDL) was 4.6 x 10(1) CFU per tomato. There was no significant difference in performance between the FTI-XLD method and the BAM Salmonella culture method (P > 0.05); however, the FTI-XLD method reduced the overall assay time by 48 h. For real-time PCR and FTI-PCR, the observed LDLs were 4.6 x 10(1) and 9.2 x 10(0) CFU per tomato, respectively. The FTI-PCR method was superior to the BAM Salmonella culture method (P < 0.05) for the detection of Salmonella serovars on tomato surfaces and was completed within 8 h.