Evaluation of DNA extraction methods for detection of Listeria monocytogenes in meat products

Objective.To evaluate two methods for extracting DNA from Listeria monocytogenes from artificially contaminated food samples. Materials and methods. The effects of different extraction methods on pure cultures of L. monocytogenes. The best performing methods were evaluated in artificially contaminated samples of meat products (ham, sausage and chorizo). To assess the quality of the extracted DNA, DNA concentration and A260/A280 ratio were determined, and the hlyA gene of L. monocytogenes was amplified by PCR. Results. The methods with organic solvents and with PBS+Tween 20 allowed to obtain more DNA (40 and 50 mg, respectively). In food samples, DNA was obtained with higher purity through the organic solvent method (p<0.005), but the method with PBS+Tween 20 resulted in higher concentration. hlyA gene amplification in samples contaminated with 1 to 105 CFU /ml was obtained through both methods of DNA extraction. The composition of the food did not affect the PCR reaction in DNA samples obtained by the two extraction methods. Conclusions. Regardless of the extraction method used, the detection of hlyA gene of L. monocytogenes in food contaminated samples with 1 to 105 CFU / ml was achieved. However, for use as a routine diagnostic method, the method with PBS + Tween 20 is a better option for DNA extraction, as a method of easy application, low cost and good performance.