Plasmids Coding for Colonization Factor Antigens I and II, Heat-Labile Enterotoxin, and Heat-Stable Enterotoxin A2 in Escherichia coli

摘要

Colonization factor antigens I and II (CFA/I and CFA/II) are important in the pathogenesis of diarrhea in human caused by some enterotoxigenic Escherichia coli (ETEC). Plasmid DNA from 16 CFA/I+ and five CFA/II+ ETEC were examined by Southern blot analysis with enterotoxin gene probes, and compared with plasmid DNA from derivatives of these ETEC that had lost the ability to produce these colonization factors. Among 16 CFA/I+ ETEC strains, loss of CFA/I was accompanied by the loss of a plasmid of between 34 and 68 megadaltons (Mdal) coding for ST-A2 in twelve strains, with the loss of a 60 Mdal plasmids coding LT and ST-A2 in one strain, or with deletions of a segment of DNA encoding for ST-A2 in three strains. Among five CFA/II+ ETEC strains, loss of CFA/II was associated with the loss of a plasmid of 75 Mdal coding for LT and ST-A2 in three strains, the loss of genes coding for LT and ST-A2 from a 68 Mdal plasmid in one strain, or with no discernible loss of a plasmid or DNA sequences coding for enterotoxins in the remaining strain. The loss of CFA/I and CFA/II production was associated with the loss of DNA sequences encoding for ST-A2 in 20 of 21 ETEC examined.