Can a fecal (stool) sample be stored in the fridge?

Proper Storage of Fecal Samples

Yes, fecal samples can be refrigerated at 4°C for short-term storage, ideally for no longer than 6 hours before processing. 1

Optimal Storage Conditions for Fecal Samples

Immediate Collection and Short-term Storage

• Fecal samples should ideally be collected in a specific single-use container 1
• After collection, samples should be:
  • Cooled to 4°C immediately after collection 1
  • Transported to the processing facility as soon as possible 1
  • Processed within 6 hours of defecation 1

Temperature Requirements

• For short-term storage (up to 6 hours): 4°C (±2°C) 1
• For longer-term storage:
  • Up to 2 months: -20°C 1
  • Up to 6 months: -80°C 1
  • Up to 2 years: -80°C 1

Storage Considerations

• Avoid repeated freeze-thaw cycles as they significantly reduce microbial viability 1
• If samples need to be stored for clinical testing purposes, refrigeration at 4°C can preserve samples for up to 60 days for diagnostic testing 2
• For microbiome research, storage at room temperature for up to 24 hours or at 4°C for up to 24 hours does not significantly alter the microbial community structure 3

Practical Recommendations

For Clinical Samples

1. Collect the sample in a clean, leak-proof container
2. Place immediately in refrigerator (4°C) if not being processed right away
3. Process or transfer to long-term storage within 6 hours of collection
4. For samples intended for fecal microbiota transplantation (FMT), label with unique identification and date of collection 1

For Research Samples

• If studying microbial composition:
  • Aliquot samples before initial freezing to avoid multiple freeze-thaw cycles 1
  • For long-term storage, use -80°C with a cryoprotectant (e.g., glycerol at 10% final concentration) 1
  • Record any temperature excursions during storage 1

Common Pitfalls to Avoid

• Allowing samples to remain at room temperature for extended periods, which permits bacterial growth and alters microbial composition 1
• Multiple freeze-thaw cycles, which significantly reduce bacterial viability 1
• Using warm water baths for thawing frozen samples, which introduces risk of contamination with Pseudomonas and other contaminants 1
• Storing samples without proper labeling for identification and traceability 1

By following these guidelines, the integrity of the fecal sample can be maintained for appropriate clinical or research applications.