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J Clin Microbiol. 2018 Jun 25;56(7). pii: e00426-18. doi: 10.1128/JCM.00426-18. Print 2018 Jul.

Evaluation of the Use of Rectal Swabs for Laboratory Diagnosis of Clostridium difficile Infection.

Author information

1
Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany nathalie.jazmati@uk-koeln.de.
2
German Centre for Infection Research (DZIF), partner site Bonn-Cologne, Germany.
3
Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany.
4
Department I of Internal Medicine, University Hospital of Cologne, Cologne, Germany.

Abstract

For the diagnosis of Clostridium difficile infection (CDI), microbiological testing is almost always accomplished through the analysis of stool specimens. We evaluated the performances of rectal swabs with liquid transport medium (FS) and nylon flocked dry swabs for the detection of C. difficile Additionally, the impact on the diagnostic yield of storing swabs at -80°C for up to 3 months was evaluated. Sixty clinical stool samples positive for C. difficile by PCR were used for simulating rectal swabbing. FS and dry swabs were dipped into the stool and tested by PCR directly after swabbing at 1 and 3 months after storage at -80°C. Stool and the liquid medium of FS were additionally tested by a combination of glutamate dehydrogenase antigen (GDH) testing and toxin A/B enzyme immunoassay (EIA), as well as by toxigenic culture (TC). Using dry swabs, the PCR-based detection rate of C. difficile was equal to the rate using stool samples (30/30 [100%]), whereas the detection rate in FS was significantly lower (25/30 [83.2%]; P = 0.019). The sensitivities of FS for detecting C. difficile by PCR, TC, GDH testing, and toxin A/B EIA were 83.3%, 85.7%, 88%, and 68.9%, respectively. Storage of swabs at -80°C had no impact on the detection rate. FS cannot replace stool samples in the two-step laboratory diagnosis of CDI, as the sensitivities were too low, probably due to diluting effects of the fecal sample in the liquid medium. For simple PCR-based detection of C. difficile, dry swabs proved to be a suitable alternative to the use of stool samples.

KEYWORDS:

Clostridium difficile

PMID:
29720433
PMCID:
PMC6018322
DOI:
10.1128/JCM.00426-18
[Indexed for MEDLINE]
Free PMC Article

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