Whole genome sequencing and revivification of freeze-dried nontuberculous mycobacteria after more than half a century of storage.

We analyzed 28 “historical” freeze-dried non-tuberculous mycobacterial isolates collected from 1948-1957, by investigating their viability and performing whole-genome sequencing (WGS) on DNA extracted a) directly from freeze-dried cells versus b) after culturing. The isolated DNA was sequenced on the Illumina MiSeq platform and data quality evaluated analyzing the per-base quality scores of paired-end sequencing reads as well as the overall contiguity of resulting de novo assemblies. After up to 72 years in storage, all freeze-dried isolates were viable, showed no signs of cell damage and little to no signs of contamination.