Figure 1.

A typical BoNT/A positive control from the Bruker MALDI Biotyper has an intact peptide substrate at 2406 m/z and two peptide fragments at 998 and 1426 m/z (1A); One patient exhibited negative BoNT/A in serum (1B, 14-17944-01); however, a low concentration of BoNT/A was detected by MS in stool from the same patient (1C, 14-17944-02), whereas the mouse bioassay was negative for both specimen types. The patient specimen results were later confirmed when the contaminated food the patient ingested was positive for BoNT/A by MS (1D, 14-18209) and the mouse bioassay.