Medical Microbiology & Diagnosis

Fecal specimens for Clostridium difficile Diagnostic Testing are Stable for up to 72 hours at 4°C

Abstract

Michelle J Alfa, Nancy Olson and Brenda-Lee Murray

Background: Clostridium difficile testing for stool specimens transported from remote geographic locations is a challenge due to long transit times that are often at room temperature. The impact of storage at room temperature versus 4°C on Clostridium difficile diagnostic tests during transport of stool samples has not been well studied. Methods: This study assessed the impact of storage at room temperature versus 4°C for up to 72 hours on the stability of glutamate dehydrogenase antigen, Toxin A and B antigens, toxigenic culture and cytopathic effect testing. Twelve diagnostic stool samples that were tested on the day of collection and shown to be C. difficile toxin positive were used for this study. Sample aliquots of each stool were stored at room temperature and 4°C and testing was repeated at 24, 48 and 72 hours. Results: The glutamate dehyrdogenase antigen and toxigenic stool culture tests were shown to be 100% reproducible at room temperature and 4°C for up to 72 hours. Toxin A and B antigen deteriorated to 70% by 72 hours at room temperature but was 90% reproducible if held at 4°C. The cytopathic effect assay was 90% reproducible by 72 hours at room temperature and 4°C. Conclusions: Based on our data we recommend that for laboratories receiving stool samples from remote regions where transit may be prolonged that glutamate dehydrogenase antigen screening followed by nucleic acid amplification testing may be a feasible diagnostic algorithm.