Open AccessAssessment of Clostridium difficile Infections by Quantitative Detection of tcdB Toxin by Use of a Real-Time Cell Analysis System
Author(s) -
Alex B. Ryder,
Ying Huang,
Haijing Li,
MingHua Zheng,
Xiaobo Wang,
Charles W. Stratton,
Xiao Yun Xu,
Yi Tang
Publication year - 2010
Publication title -
journal of clinical microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.349
H-Index - 255
eISSN - 1070-633X
pISSN - 0095-1137
DOI - 10.1128/jcm.01104-10
Subject(s) - clostridium difficile toxin a , clostridium difficile , toxin , microbiology and biotechnology , clostridium difficile toxin b , immunoassay , glutamate dehydrogenase , vancomycin , clostridiaceae , metronidazole , biology , staphylococcus aureus , antibiotics , immunology , bacteria , antibody , biochemistry , glutamate receptor , genetics , receptor
We explored the use of a real-time cell analysis (RTCA) system for the assessment ofClostridium difficile toxins in human stool specimens by monitoring the dynamic responses of the HS27 cells totcdB toxins. TheC. difficile toxin caused cytotoxic effects on the cells, which resulted in a dose-dependent and time-dependent decrease in cell impedance. The RTCA assay possessed an analytical sensitivity of 0.2 ng/ml forC. difficile toxin B with no cross-reactions with other enterotoxins, nontoxigenicC. difficile , or otherClostridum species. Clinical validation was performed on 300 consecutively collected stool specimens from patients with suspectedC. difficile infection (CDI). Each stool specimen was tested in parallel by a real-time PCR assay (PCR), a dual glutamate dehydrogenase and toxin A/B enzyme immunoassay (EIA), and the RTCA assay. In comparison to a reference standard in a combination of the three assays, the RTCA had a specificity of 99.6% and a sensitivity of 87.5% (28 of 32), which was higher than the EIA result (P = 0.005) but lower than the PCR result (P = 0.057). In addition, the RTCA assay allowed for quantification of toxin protein concentration in a given specimen. Among RTCA-positive specimens collected prior to treatment with metronidazole and/or vancomycin, a significant correlation between toxin protein concentrations and clinical CDI severities was observed (R 2 = 0.732,P = 0.0004). Toxin concentrations after treatment (0.89 ng/ml) were significantly lower than those prior to the treatment (15.68 ng/ml, WilcoxonP = 0.01). The study demonstrates that the RTCA assay provides a functional tool for the potential assessment ofC. difficile infections.