A freeze-tolerant solid medium for detection and sampling of air-borne microorganisms at subzero temperature

We have developed a freeze-tolerant base suitable for solidification of nutrients required for sampling subzero microbial aerosols with slit samplers. The base was composed of 3% cornstarch and 3% agar. Unlike conventional agar, media prepared with this base withstood freeze and thaw processes, did not express water, and retained their structural integrity. When samples of aerosolized vegetative cells were impacted on either frozen heart infusion or SB broth containing the base, we found more well isolated colonics than when samples were collected on corresponding media at room temperature. There were no significant differences between colony yields when air-borne spores were collected on frozen and nonfrozen media.