A rapid methods for Pcr based on detection of salmonela spp. and staphylococcus aureus in spiked and naturally contaminated food

Abstract EN

A rapid method for detection of food-borne pathogens, gene specific PCR, was used to detect two kinds of bacteria ( Salmonella spp.

and Staphylococcus aureus) from food.

Cultures of artificially inoculated foods were spiked ,with reference bacteria at known concentrations and DNA was isolated from each food sample before and after enrichment, using phenol -chloroform based method, Positive results were obtained using gene specific PCR (targeting the invA gene in Salmonella spp.

and Sa 442 gene in Staphylococcus aureus ) just after enrichment step, that produced specific amplicons of the expected sizes which was 284bp in Salmonella spp.

and 108 bp in Staphylococcus aureus.

The detection limit of the assay was 103 CFU/ ml for the two kinds of bacteria.

No results were obtained using the same primers with five other types of bacterial strains which improve it s specifity.

The same technique was used for detection of the two kinds of bacteria in some naturally contaminated foods.

To achieve this, 13 food samples were collected from Sulaymani market during April-October, 2012 including meats (meat of beef, sheep, goats, fresh chicken, and frozen chicken) and vegetables (celery, tomato, cucumber, pepper, lettuce, broccoli, carrot, and leek) DNA isolated from the samples after two enrichment steps ,the results of PCR, indicate the detection of Salmonella spp., in three out of 13 food samples tested, whereas the detection of Staphylococcus aureus achieved in four out of 10 food samples tested.

This study indicate that PCR is a good way for the rapid detection of Salmonella spp and Staphylococcus aureus in food.