Studies on the Genes Encoding Botulinum Neurotoxin Type A of Clostridium botulinum from a Variety of Sources

Abstract

Summary 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 Rsa I and Sau3 Al 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 S of the 25 type A strains examined contained unexpressed type B gene sequences.