Effects of storage temperature, storage time, and transport medium (Cary Blair) for metagenomic analysis

The proper transport and storage of feces is important in microbiome studies. However, how long fecal samples can withstand a period of refrigeration or room temperature, and the appropriate preservative, are largely unknown. Cary-Blair transport medium has been used for many years because it is inexpensive (less than US$0.50) and prevents bacterial overgrowth. However, its effectiveness for metagenomic analyses has never been tested. To facilitate hospital-based or epidemiological microbiome studies, we determined the effects of the storage time, storage temperature, and Cary-Blair medium on the stability of the human gut microbiota. Microbial compositions were compared using a 16S rRNA sequence analysis after storage with different methods. The effects of Cary-Blair medium on the microbiota were also analyzed. Storage time and storage temperature significantly affect the gut microbial composition in fecal samples. Given the low cost, inhibitory effect on bacterial changes, and potential utility in bacterial isolation, Cary-Blair medium containers are suitable for large-scale or hospital-based microbiome studies.