Mechanism of spontaneous loss of heat‐stable toxin (STa) production in enterotoxigenic Escherichia coli

Abstract
Five strains of enterotoxigenicEscherichia coli(ETEC) showing spontaneous loss of heat‐stable enterotoxin (STa) production were studied to elucidate the underlying genetic mechanisms. Southern blot analysis revealed that loss of STa production, and the corresponding lack of hybridization with the STa gene probes, were associated with deletions of DNA fragments harboring the relevant toxin genes rather than with loss of plasmids.