STUDIES ON THE GENES ENCODING BOTULINUM NEUROTOXIN TYPE-A OF CLOSTRIDIUM-BOTULINUM FROM A VARIETY OF SOURCES

Degenerate oligonucleotide primers, designed to conserved regions of the heavy chain of the botulinum neurotoxin (BoNT), were used to amplify a fragment of approximately 1.1 kb from twenty-five type A Clostridium botulinum strains. These strains were isolated from different geographical locations, from both infant and food-borne botulism. Restriction fragment length polymorphism (RFLP) analysis of the PCR products with RsaI and Sau3AI revaled two different groups of BoNT/A genes, designated BoNT/A1 and BoNT/A2. These two groups did not correlate with the origin of the strains, each group containing isolates from infant and food-borne botulism. Organisms isolated from infant botulism in Japan fell into group A2 while all strains examined from the USA, from both infant and food-borne botulism, fell into group A1. Strains from other locations were as follows: food-borne isolates from the UK (groups A1 and A2), Mauritius (group A1) and Venezuela (group A1). In addition, strains encoding BoNT/A1 gave PCR products with primers designated to detect hemagglutinin genes, the products of which form part of the large progenitor toxin complex produced by some strains of C. botulinum, but strains encoding BoNT/A2 gave no such products. In addition, RFLP analysis and probing studies revealed 8 of the 25 type A strains examined contained unexpressed type B gene sequences.