Implementation of COPAN FecalSwab and COPAN Selenite on WASP for the Automated Processing of Stool Specimens
Automated processing of stool specimens is difficult due to different sample consistency, volume availability and variety of primary containers. Appropriate specimen collection and transportation systems can standardize the stool sample processing, enhancing the diagnostic process.
The objective of this study was to validate the implementation process of FecalSwab and LBM Selenite broth on WASP, for the clinical microbiology laboratory, in order to convert stool processing from the manual streaking process to an automated procedure.
Spiked negative stools and clinical stools were used for this study (n=97). Aliquots (3 grams) of the negative stools were spiked with 300 μl of diluted Y. enterocolitica serovar 3 biotype 4, S. typhimurium (ATCC 25241), S. flexneri (clinical strain) and Campylobacter jejuni (ATCC 33560) to obtain final bacterial concentrations/stool of 108 CFU/g, 107 CFU/g, 106 CFU/g. All clinical stool samples (n=61) and spiked stools in triplicate (n=36) were transferred in FecalSwabTM medium tubes using the flocked swab.
All samples were manually plated onto the first quadrant of McConkey, XLD, CIN, Campylosel agar plates using a swab and streaked with a 10 μl loop, while the FecalSwabTM stools were loaded on WASP® and processed using a 10 μL loop and a 4 quadrants streaking pattern. All clinical stool samples and the negative ones spiked with S. typhimurium (n=73), were also inoculated in LBM® Selenite broth broth, from FecalSwabTM and from the sample directly, and then plated on SS-agar after overnight incubation.
For the spiked samples we found 100% concordance for S. flexneri and C. jejuni. Discrepant results were found in the stools spiked with the lowest concentration of S. typhimurium and Y. enterocolitica, negative when manually plated but positive from FecalSwabTM and LBM® Selenite broth.
We found 100% concordance in the clinical samples with S. typhimurium and Y. enterocolitica, three Campylobacter coli were not isolated, maybe due to sampling bias. Culture via FecalSwabTM yielded two extra Aeromonas species possibly because WASP® streaked FecalSwabTM samples had more isolated colonies to perform successive analysis. LBM® Selenite broth detected all the Salmonella spp. and some additional Yersinia spp. with both WASP® and manual streaking method.
FecalSwabTM and LBM® Selenite broth are facilitating WASP® automation stool processing and are reliable devices for diagnosis of gastric infections. Automatic processing of FecalSwabTM and LBM® Selenite broth allows standardization and time reduction of sample processing.