Evaluation of TaqMan PCR assay for detecting Salmonella in raw meat and shrimp

We evaluated the TaqMan Salmonella amplification/detection kit from PE Appl ied Biosystems, which uses a polymerase chain reaction (PCR) assay for rapi d detection of Salmonella in food samples. This system uses the 5' nuclease activity of Tag DNA polymerase, which digests an internal fluorogenic prob e to monitor the amplification of the target gene. The system's sensitivity and specificity were evaluated using 42 serotypes of 68 Salmonella strains isolated from fecal samples from patients in Tokyo, Japan, and 39 non-Salm onella strains in 22 genera. There were no false-negative or false-positive results. This PCR assay can detect 3 CFU per PCR tube of Salmonella in pur e culture (120 CFU/ml of TSB culture). PCR signals were attenuated with art ificially contaminated shrimp, but a similar detection limit was obtained. TaqMan's performance was tested with 100 meat and chicken samples purchased from stores in Tokyo. Overall, two of the DNA extraction protocols (the Ch elex and EnviroAmp methods) worked equally well, with some exceptions. Of t he 100 samples analyzed, 10 were positive for Salmonella with both conventi onal culture methods and the kit and 89 were negative with both. One sample was negative by the culture method but positive by the kit assay. These re sults indicate that TaqMan is a reliable and rapid method for Salmonella an alysis in the food industry. With this system, food samples can be analyzed for Salmonella in less than 20 h.