THE CLOSTRIDIUM-PERFRINGENS ENTEROTOXIN GENE IS ON A TRANSPOSABLE ELEMENT IN TYPE-A HUMAN FOOD POISONING STRAINS

The Clostridium perfringens enterotoxin gene (cpe) is rarely found in naturally isolated strains. In human food poisoning strains, cpe is fo und on the chromosome, and is located episomally in animal isolates. O bservations that the gene was somewhat unstable and could be gained or lost suggested that the gene was on a mobile element. An IS200-like e lement, IS1469, is almost always upstream of cpe. A new insertion elem ent was identified, IS1470, a member of the IS30 family, which is foun d both up- and downstream of cpe in the type A strain NCTC 8239. PCR r esults confirmed that this configuration was conserved in type a human food poisoning strains. The enterotoxin gene was on a 6.3 kb transpos on which. in addition to the two flanking copies of IS1470, included I S1469 and two 1 kb stretches, one on each side of cpe, with no open re ading frames. Results indicated that 14 bp was copied from the genome during insertion. Details of the configuration of DNA in this transpos on are presented, and the possible connection of this transposon with the movement of the enterotoxin gene is discussed.