Fecal specimens have been utilized in the microbiology laboratory for years in order to detect bacterial gastrointestinal (GI) pathogens by culture. More recently, molecular assays have been developed to detect not only bacterial GI pathogens, but viral and parasitic causes of diarrhea as well. Fresh, unpreserved stool specimens in addition to Cary-Blair preserved stool specimens can be used for culture and molecular assays. However, bulk fecal collections are not without challenges! They are oftentimes difficult and messy to place into sterile containers or Cary-Blair media for transport to the laboratory. Also, producing a stool specimen on demand, especially for children, can prove to be difficult.  Thus, the use of the FecalSwab® (COPAN Diagnostics, Murrieta, CA) has made obtaining these specimens much more ‘user-friendly’.  FecalSwabs® comes as a straight-shafted swab for a sampling of stool from a container, or with a molded stopper (or depth gauge) so rectal specimens are appropriately taken from the “transitional zone” between the dentate line and the anorectal ring.  In addition, scientific studies have shown that the FecalSwabs® works well for both culture of bacterial pathogens and for the molecular detection of GI pathogens including viruses and parasites.

The study by Goldfarb and colleagues evaluated 280 matched bulk stool and rectal FecalSwab® samples collected from children admitted to the hospital with acute diarrhea in Botswana (1).  All samples were tested by a commercial
multiplex PCR assay (Gastrointestinal Pathogen Panel (GPP) assay (Luminex Molecular Diagnostics, Toronto, Canada). The flocked swabs had a 12% higher yield for bacterial pathogen targets compared with that of the bulk stool samples, as well as similar yields for viral and parasitic targets.

Almost all of the children’s parents and guardians found the FecalSwab® an acceptable method for collection of stool specimens.  These authors concluded that FecalSwab® significantly facilitated the molecular diagnosis of diarrheal disease in children. Likewise, the study by Kellner et. al. evaluated paired rectal flocked swab specimens from emergency
room patients placed into Cary-Blair medium and used for bacterial culture and placed into sterile containers without medium and used for testing in the molecular GPP assay (2). Their study showed that the overall agreement between the molecular assay and bacterial culture was excellent.

Several additional studies have shown that the FecalSwab® works well in other molecular assays.  Silbert and colleagues studied a total of 103 clinical stool samples in the FilmArray GI Panel using two different protocols: A) the standard of care (SC) using fresh stool samples added to Cary-Blair medium, and B) FecalSwab® (FS) placed into fresh stool samples and then transferred to Cary-Blair media.  The results of the 0-hour and 24-hour stored FS tested in the FilmArray assay were equivalent to those obtained when using SC.  The rate of discrepant results observed between the SC and FS collections was less than 3%. These authors concluded that the FecalSwab® can be used to process raw stool samples prior to testing with the FilmArray GI Panel.

The study of Chapin et. al. evaluated over 100 pediatric patients presenting with acute gastroenteritis where both a rectal FecalSwab® (FS) and a Cary-Blair (CB) stool were collected and tested in the FilmArray and BD MAX GI pathogen assays (4).  The comparison showed complete agreement between the FS and CB collections in both molecular assays for the detection of Salmonella, Shigella, STEC and Campylobacter.  FS also allowed the analysis of an additional 9% of patients that otherwise would not have been tested (unable to produce a stool specimen at the time of care) and the FS was found to be more acceptable for younger patients.

The study by Jean and colleagues evaluated 480 paired flocked rectal swab specimens and bulk fecal specimens submitted for enteric culture (5).  They reported an overall agreement of 93%. Additionally, they evaluated the time to result from the time of patient presentation to the health care setting and demonstrated that the flocked rectal swabs had a significantly shorter time to an actionable result as compared to the bulk fecal specimens (median, 67.4 h versus 78.4 h, respectively; P_0.001). Their findings indicate that flocked rectal swabs facilitate on-demand culture-based testing with a sensitivity comparable to that of bulk fecal specimens and can be recommended for enteric bacterial culture.

Lastly, but importantly, Maschock et. al. performed a study to evaluate the performance of specimens collected in FecalSwab® as compared to unpreserved stools using the Cepheid Xpert C. difficile assay (Cepheid, Sunnyvale, CA) (6). They found that using 400 µl of FecalSwab® preserved stool was equivalent to unpreserved stool specimens when tested in the Xpert assay. Only 4 discrepant results occurred during the study and post-discrepant analysis using the BD MAX™ Cdiff assay (Becton-Dickinson, Heidelberg, Germany) increased the specificity and sensitivity to 100%. They concluded that the high positive and negative percent agreements observed in their study suggests that stool preserved in FecalSwab® yields equivalent results to unpreserved stool when tested on the Xpert C. difficile assay, allowing laboratories to adopt the FecalSwab® device for this test system.

Whether performing culture for bacterial pathogens as the cause of gastroenteritis or using a molecular assay for the detection of bacterial, viral, and/or parasitic causes of diarrhea, COPAN FLOQSwabs® allow for a versatile collection and
transport system suitable for enteric pathogen recovery.  Thus, regardless of the testing system used in the laboratory, COPAN’s FecalSwab® offers a liquid-based collection device for the accurate and timely detection of gastrointestinal pathogens from fecal or rectal specimens.

*Always read the manufacturer’s package insert
for specific instructions regarding specimen collection and transport for the
type of test kit being used.

References:

1. Goldfarb DM, Steenhoff AP, Pernica JM, Chong S, Luinstra K, Mokomane M, Mazhani L, Quaye I, Goercke I, Mahony J, Smieja M. 2014. Evaluation of anatomically designed flocked rectal swabs for molecular detection of enteric pathogens in children admitted to hospital with severe gastroenteritis in Botswana. J Clin Microbiol 52:3922–3927.
2. Kellner, T., Parsons, B., Chui, L., Berenger, B.M., Xie, J., Burnham, C.A. et al, Comparative evaluation of enteric bacterial culture and a molecular multiplex syndromic panel in children with acute gastroenteritis. J Clin Microbiol. 2019;57.
3. Silbert S, Gostnell A, Kubasek C, Widen R. 2017. Evaluation of the new FecalSwab system for maintaining stability of stool samples submitted for molecular tests. J Clin Microbiol 55:1588 –1590.
4. Chapin K, Duffy S, LeBlanc L, Bushey E, Prahash VP, Raposo M.  2016. Evaluation of Two Multiplex Molecular GI Panels using Rectal Swab Specimens Versus Cary-Blair Stool in Pediatric Patients with Acute Gastroenteritis. Poster Abstract Session: Clinical Infectious Diseases: Enteric Infections Open Forum Infectious Diseases, Volume 3, Issue suppl_1, December 2016, 1214, https://doi.org/10.1093/ofid/ofw172.917.
5. Jean S, Yarbrough ML, Anderson NW, Burnham C-AD. 2019. Culture of rectal swab specimens for enteric bacterial pathogens decreases time to test result while preserving assay sensitivity compared to bulk fecal specimens. J Clin
   Microbiol 57:e02077-18.
6. Mashock MJ, Faron ML, Buchan BW, Ledeboer NA. 2017. Evaluation of Copan FecalSwab as specimen type for use in Xpert C.difficile assay. J Clin Microbiol 55:3123–3129.