Rapid detection of Salmonella in poultry by enrichment broth cultivation-PCR assay

Abstract

Polymerase chain reaction (PCR) was used to detect Salmonella in faecal and meat samples using a primer set of oligonucleotides for invA gene. Poultry faecal and meat samples which were negative for the organism, were spiked with different dilutions of Salmonella Typhimurium that was given pre-enrichment in buffered peptone water (BPW) at 2 h and 6 h period. PCR was carried out using DNA templates by boiling-centrifugation and the limit of detection was established. At 2 h pre-enrichment, PCR was able to detect S. Typhimurium up to the concentration level of 2 × 107 CFU/ml, while 6 h pre-enrichment increased the detection limit to 2 × 104 CFU/ml with spiked poultry faecal samples. From spiked meat it was observed that at 2 h pre-enrichment limit of detection was 2 × 105 CFU/ml, while 6 h pre-enrichment increased the detection limit to 2 × 102 CFU/ml. The assay was able to detect the Salmonella after 2 h and its sensitivity increased after 6 h of pre-enrichment in BPW. As results were obtained in a shorter time-period than that of microbiological culture, this method will be useful in the rapid detection of Salmonella from faecal and meat samples.