Real-time cellular analysis for quantitative detection of functional Clostridium difficile toxin in stool

Abstract

Rapid and accurate diagnosis and monitoring of Clostridium difficile infection (CDI) is critical for patient care and infection control. We will briefly review current laboratory techniques for the diagnosis of CDI and identify aspects needing improvement. We will also introduce a real-time cellular analysis (RTCA) assay developed for the diagnosis and monitoring of CDI using electronic impedance to assess the cell status. The RTCA assay uses impedance measurement to detect minute physiological changes in cells cultured on gold microelectrodes embedded in glass substrates in the bottom of microtiter wells. This assay has been adapted for quantitative detection of C. difficile functional toxin directly from stool specimens. Compared to conventional techniques and molecular assays, the RTCA assay provides a valuable tool for the diagnosis of CDI as well as for the assessment of clinical severity and for monitoring therapeutic efficacies.

Keywords::

• Clostridium difficile
• detection
• quantification
• real-time cellular analysis
• toxin

Financial & competing interests disclosure

This work was supported in part by a research contract between the Memorial Sloan-Kettering Cancer Center and the ACEA Biosciences awarded to Y-W Tang (SK2012-0172). The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Rapid and accurate laboratory diagnosis and monitoring of Clostridium difficile infection (CDI) are critical to initiate appropriate treatment, reduce the morbidity from CDI and allow the implementation of specific infection control measures.

• Current conventional and molecular techniques being used for detection and identification of C. difficile in the clinical laboratory merit further improvements.

• C. difficile toxin level correlates with clinical CDI severity. Techniques for C. difficile functional toxin quantitative detection are useful adjunct to current diagnostic tests.

• The real-time cellular analysis (RTCA) assay has been used for quantitative detection of C. difficile active and functional toxin. The RTCA assay displayed the limitation of detection of 0.12 ng/ml for C. difficile toxin B with satisfied analytical and clinical sensitivities and specificities.

• C. difficile toxin concentration in stool specimens derived from the RTCA assay corelates with clinical CDI severity and may be used as a marker for monitoring the status of CDI.