Detection of the enteroaggregative Escherichia coli heat-stable enterotoxin 1 gene sequences in enterotoxigenic E-coli strains pathogenic for humans

The sequence of the enteroaggregative Escherichia coli enterotoxin 1 (EAST1) gene was present in most (or all) strains of human-colonizing enterotoxigenic E. coli (ETEC) with colonization factor antigen II (CFA/II) or CFA/IV (CS6). The EAST1 gene was also strongly associated with PCF09(+) ETEC or CFA/I+ ETEC elaborating heat-labile enterotoxin (and heat-stable enterotoxin I). In contrast, CFA/I+ ETEC elaborating heat-stable enterotoxin I, CFA/III+ ETEC, or CS17(+) ETEC exhibited very weak or no association. E. coli from healthy volunteers had no EAST1 gene sequence. A CFA/I+ ETEC strain (H10407) possessed multiple copies of the EAST1 gene on the CFA/I-encoding plasmid and chromosome. In one CFA/II+ ETEC strain, the EAST1 gene was present on the CFA/II-encoding plasmid. The EAST1 gene sequences of the CFA/I+ and CFA/II+ ETEC strains were identical to each other and 99.1% homologous to the reported gene sequence of enteroaggregative E. coli. The data indicate that the EAST1 gene is distributed among ETEC strains with a case of the presence of multiple copies in a single cell and that this distribution is associated with the adherence factor type.