Background: In the United States, most Clostridium botulinum type A strains isolated during laboratory
investigations of human botulism demonstrate the presence of an expressed type A botulinum neurotoxin (BoNT/
A) gene and an unexpressed BoNT/B gene. These strains are designated type A(B). The most common pulsed-field
gel electrophoresis (PFGE) pattern in the C. botulinum PulseNet database is composed of A(B) strains. The purpose
of this study was to evaluate the ability of genome sequencing and multi-loci variable number of tandem repeat
analysis (MLVA) to differentiate such strains.