Novel UNEX Buffer and Disk for Safe Storage and Transport at Ambient Temperatures of Clinical Specimens for Molecular Testing of Pathogens

The development of genomic approaches and nucleic acid based techniques has led to a large number of biological samples, including DNA, RNA, cells, tissues, and environmental samples that require storage. Typically, microbial DNA and RNA samples are stored long-term in laboratory freezers at temperatures ranging from -20°C to -196°C, the lower ranges utilizing liquid nitrogen. This often requires the use of several freezer boxes that can take up space and become difficult to sort through. Additionally, freezer equipment and cold chain transport measures needed for specimen stability are costly and difficult to maintain over time.

CDC developed the universal nucleic acid extraction (UNEX) buffer and disk for stable storage and transport of microbial samples at ambient (room) temperatures, bypassing the need for expensive cold chain (dry-ice) transit. Microbial RNA and DNA in water samples were stable for more than 2 years and 6 months (951 days) in UNEX lysis buffer stored at 4o C. The UNEX buffer inactivates bacteria (e.g., Salmonella serovar Typhimurium, and E. coli) and viruses (e.g., measles, adenovirus, poliovirus and three different strains of Middle East Respiratory Syndrome (MERS) Coronavirus, hepatitis A virus) tested thus far. In addition, a simple heat-elution step enables successful post specimen recovery of microbial RNA and DNA for up to 3 months from UNEX buffer treated cellulose- disks (UNEX disks). CDC’s invention inactivates pathogens and stores total nucleic acid (DNA and RNA) versus current commercial cards that primarily target either DNA or RNA storage only. This technology has great potential as nucleic acid transport and storage media for microbial specimens prior to molecular testing. This can help meet a critical need for safe and inexpensive shipping of nucleic acids from microbial specimens potentially containing pathogens, especially in resource-limited settings.