EVALUATION OF DIFFERENT DNA EXTRACTION PROCEDURES FOR THE DETECTION OF SALMONELLA FROM CHICKEN PRODUCTS BY POLYMERASE CHAIN-REACTION

Polymerase chain reaction (PCR) was used after a short pre-enrichment culture to detect Salmonella subspecies in chicken fillets. A direct P CR assay performed with chicken meat inoculated with Salmonella Typhim urium produced no PCR products. Six different DNA extraction protocols were tested to recover efficiently Salmonella DNA after a short incub ation period. Three of them gave results that were reliable, rapid and sensitive. Successful protocols used Proteinase K and/or a centrifuga tion step to concentrate the samples. For reliable detection of Salmon ella subspecies, a few thousand bacterial cells per mi must be present . To obtain this number of bacterial cells with an inoculation of abou t one cell in 25 g of ionized food products, it was necessary to incub ate samples for at least 10 h before PCR. A larger inoculum of approxi mately 10 cells in 25 g of ionized food products, required 8 h in cult ure broth to give positive results by PCR-based assay.