Storage and repeated recovery of Neisseria gonorrhoeae using cryovials

One hundred gonococcal isolates, representing eight protein IA serovars and 14 protein IB serovars, were stored at -70 degrees C using the Pro-Lab Microbank cryovial storage system. At monthly intervals a bead from each cryovial was removed and cultured on modified New York City medium. The overall recovery rate was 98.6% (2365/2400), the 35 failures representing 13 separate isolates. There was a small but significant decrease in recovery in the last 12 months of the trial (97.8%) compared with the first 12 months (99.8%), which may have been due to a sampling problem rather than a temporal phenomenon. Failures were significantly associated with minor serovars, suggesting that the transmissibility/viability of minor serovars may be lower than that of common serovars and could be a significant factor in the epidemiology of gonococcal infection. We conclude that Pro-Lab Microbank cryovials provide a highly effective and convenient system for storage of Neisseria gonorrhoeae, particularly when multiple retrieval is required, and the system offers many advantages over conventional lyophilisation.