Clostridium Difficile Toxin B - Function - Toxin Detection

Toxin Detection

There are different plasmid sizes of C. difficile. The detected molecular weights range from 2.7x106 to 100x106, but plasmid sizes show no correlation with toxicity. In order to detect the toxin B level in C. difficile, clinicians extensively use cell culture assays derived from stool specimens from patients with PMC. The cell culture assay is regarded as a “gold standard” for detecting toxicity in C. difficile because a small quantity of toxin B is capable of causing cell rounding (Fig. 4), thus, it is a major advantage of clinical laboratories to make correlations with the CDAD caused by TcdB. Although cytotoxic activity of large clostridial toxins (LCTs) was found in PMC patient stool specimens, toxin B activity had more detrimental cytotoxic effects in comparison with toxin A. Therefore, the activity of toxin A is attenuated when it is not isolated from toxin B. The detection of C. difficile toxicity is extremely sensitive, however, using the cell culture assay allows clinical laboratories to overcome the challenge; using doses as little as 1 pg/mL of toxin B is enough to causes cell rounding. This is the major advantage in using the culture tissue assay to detect toxicity in PMC patients. Even though clinical laboratories have tried to use an assay microtiter plate enzyme-linked immunosorbent assay (ELISA) and other techniques to detect the cytotoxic activity of toxin B in the feces of PMC patients, the results are not as accurate as those where cell culture assays were used.