A new ultrasonic high-throughput instrument for rapid DNA release from microorganisms

Rapid detection methods for microbiological contamination are requested by many industries that respond to public health concerns. The control laboratories are replacing traditional culturing methods with faster assays based on nucleic acid amplification technologies, such as real-time PCR. However, an optimal nucleic acid sample preparation method is critical for the sensitivity and specificity of such tools. A high-throughput automated external ultrasonic device was developed for rapid lysing of microorganisms. Based on Ct values obtained from real-time PCR, there was efficient DNA release from the 16 microorganisms tested, including Gram positive and negative bacteria, bacterial spores, yeasts and spores of molds. Linearity of the lysis method was also demonstrated for Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella enterica, Candida albicans and the spores of Aspergillus brasiliensis, with correlation coefficients (r(2)) between 0.90 and 0.98. After sonication, PCR analysis of the lysates revealed earlier Ct values (0.83 to 7.49) for S. aureus, P. aeruginosa and S. enterica compared to the bead-beating method of lysis. These results demonstrated more efficient DNA release from bacteria with the ultrasonication system. Nevertheless, for fungi, the Ct values were 0.94 to 1.61 later for sonication than for bead beating. This study demonstrates that 4min of sonication with this new automated high-throughput instrument allows for the efficient lysis of a large range of microorganisms.