P-Y Cheung1, C W Chan, W Wong, T L Cheung, K M Kam. 1. Department of Health, Public Health Laboratory, Public Health Laboratory Centre, Hong Kong, China. cheungpi@yahoo.com
Abstract
AIMS: To evaluate the LightCycler Salmonella Detection Kit and the TaqMan Salmonella Gold Detection and Quantitation Kit for the real-time PCR detection of Salmonella in various food samples. METHODS AND RESULTS: Ready-to-eat foods and raw food samples were artificially contaminated with Salmonella serotypes. In the specificity test, bacterial DNA extracted from sample pre-enrichment culture was analysed with the detection kits performed respectively on the LightCycler Instrument or the ABI Prism 7000 Sequence Detection System. No false-positive or false-negative results were obtained, although the LightCycler system generated invalid PCR results on two occasions. In the sensitivity test using the LightCycler system, Salmonella could be detected in pre-enrichment cultures of 25-g samples inoculated with as low as 1.5 x 10(3) CFU (depending on food type), and false-negative results were obtained for samples with low inoculum levels. CONCLUSIONS: Two commercial kits for real-time PCR detection of Salmonella were evaluated. SIGNIFICANCE AND IMPACT OF THE STUDY: Evaluation using more food types and matrices, and foods that contain low number of Salmonella or high number of other competing bacteria, is needed before adopting the real-time PCR technique for routine food tests.
AIMS: To evaluate the LightCycler Salmonella Detection Kit and the TaqMan Salmonella Gold Detection and Quantitation Kit for the real-time PCR detection of Salmonella in various food samples. METHODS AND RESULTS: Ready-to-eat foods and raw food samples were artificially contaminated with Salmonella serotypes. In the specificity test, bacterial DNA extracted from sample pre-enrichment culture was analysed with the detection kits performed respectively on the LightCycler Instrument or the ABI Prism 7000 Sequence Detection System. No false-positive or false-negative results were obtained, although the LightCycler system generated invalid PCR results on two occasions. In the sensitivity test using the LightCycler system, Salmonella could be detected in pre-enrichment cultures of 25-g samples inoculated with as low as 1.5 x 10(3) CFU (depending on food type), and false-negative results were obtained for samples with low inoculum levels. CONCLUSIONS: Two commercial kits for real-time PCR detection of Salmonella were evaluated. SIGNIFICANCE AND IMPACT OF THE STUDY: Evaluation using more food types and matrices, and foods that contain low number of Salmonella or high number of other competing bacteria, is needed before adopting the real-time PCR technique for routine food tests.