Application of a rapid nucleic acid extraction kit in detection of influenza virus nucleic acid

Objective To evaluate the applicability and effectiveness of a rapid nucleic acid extraction kit in the detection of influenza virus. Methods Ten-fold dilutions from influenza virus (one H3 strain, one BY cell strain and one pdm09 H1N1 embryo strain) and 67 throat swabs positive for influenza virus collected in Beijing in 2015 were selected for the study. The viral nucleic acids were extracted by the novel rapid extraction method and spin column extraction method simultaneously. Real-time fluorescent PCR were used for qualitative and quantitative detections, and the results were analyzed with software SPSS 19.0. Results For the influenza virus cell strain and embryo strain, the detection limitation of the rapid extraction kit for influenza virus nucleic acid was 10 times higher than that of the spin column extraction method and 100 times higher than that of swab detection. The virus load detected by rapid extraction was lower than that by spin column extraction (10 times lower for samples with more viral particles and 100 times lower for swabs with less viral particles). For the stability, the rapid extraction kit was better than the spin column extraction method. The nucleic acid loss caused by rapid extraction due to re-freezing and re-thawing at -80℃ for 10 days was greater than the spin column extraction. Based on the quantitative detection results of spin column extraction, 67 swabs were divided into different viral load groups. By real time RT-PCR for qualitative detection, the total positive consistent rate for rapid extraction and spin column extraction was 92.54%. For the 10-102 copies/ml group, the positive consistent rates were 76.92%, 92.59% for 102-103 copies/ml group, 100% for103 copies/ml group. Conclusion The novel rapid nucleic acid extraction kit has some advantages such as high stability, easy to operate, hard to be polluted, and is appropriate for the nucleic acid extraction from the strains such as cell culture fluid, chick embryo culture fluid which contain more viral particles. Though the novel rapid nucleic acid extraction was more suitable for grass root laboratories which deal with large number of samples, lack staff and equipment, it is not appropriate to use nucleic acid after re-freezing and re-thawing due to the loss of nucleic acid after freezing at -80℃.The traditional spin column extraction method has advantages for the nucleic acid extraction from swabs which contain less viral particles and is more appropriate for the nucleic acid to be reused after re-freezing and re-thawing.