Figure 4. Detection of TcdA in clinical C. diff samples using TcdA-specific mAb 5D8/2C7-HRP pair by sandwich ELISA. (A) Detection of TcdA toxin in blinded clinical samples using mAb 5D8/2C7-HRP sandwich ELISA and commercial TcdA detection kit “Remel X/pect.” OD values, >0.1 in 5D8/2C7-HRP sandwich ELISA were considered as positive. The results “(+)” and “(-)“ indicate positive or negative for TcdA toxin in Remel X/pect assays, respectively. S1 – S12 were clinical samples, and NC was negative control using PBS. (B) Quantitative detection of TcdA toxin in clinical samples. The graph on the left is an example of the standard curve of commercial TcdA detected by mAb 5D8/2C7-HRP pair in a sandwich ELISA. The table on the right is a list of TcdA toxin amount in clinical samples B1-B5 as determined by mAb 5D8/2C7-HRP pair in sandwich ELISA.