Development of a method for alkaline extraction of DNA from Brucella for diagnosing brucellosis using the polymerase chain reaction

Several methods of alkaline extraction of chromosome DNA from Brucella in the presence of 50 microliters model diagnostic material blood serum are developed for the diagnosis of brucellosis by the polymerase chain reaction (PCR). These methods are based on the capacity of NaOH to effectively denature proteins and destroy Brucella cell wall, thus isolating the genome DNA without exposure to proteolytic enzymes, detergents, deproteinization, or pH neutralization. The first method consists in alkaline lysis by 0.2-1.0 M NaOH followed by DNA precipitation with two ethanol volumes in the presence of 0.1 M NaCl, washing of the resultant precipitate in 80% ethanol, drying of the precipitate, and dissolving in distilled water. The second method includes alkaline lysis in the presence of 0.3 M NaCl with NaOH concentrations of 0.5-4.3 M and the stages of DNA sedimentation, washing of precipitate, its drying and dissolving similar to those in alkaline lysis. The third method consists in alkaline lysis-precipitation by 0.2-05 M NaOH in the presence of 0.1 M NaCl and 64% ethanol, followed by DNA preparation stages similar to those in alkaline lysis. The best results were achieved by alkaline lysis in the presence of 0.3 M NaCl at NaOH concentrations of 0.7 and 2.1 M, which meant theoretical levels of sensitivity 140 and 86 Brucella cells, respectively.