Initial recovery and rebound of type f intestinal colonization botulism after administration of investigational heptavalent botulinum antitoxin.

Investigational heptavalent botulinum antitoxin (HBAT) is now the primary antitoxin for US noninfant botulism patients. HBAT consists of equine Fab/F(ab')2 IgG fragments, which are cleared from circulation faster than whole immunoglobulins. Rebound botulism after antitoxin administration is not previously documented but occurred in our patient 10 days after HBAT administration.