Plasmids coding for colonization factor antigens I and II, heat-labile enterotoxin, and heat-stable enterotoxin A2 in Escherichia coli

Abstract

Colonization factor antigens I and II (CFA/I and CFA/II) are important in the pathogenesis of diarrhea in humans 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 were compared with plasmid DNA from derivatives of the same ETEC that had lost the ability to produce these colonization factors. Among the 16 CFA/I+ ETEC strains, the loss of CFA/I was accompanied by the loss of a plasmid of between 34 and 68 megadaltons (MDa) coding for heat-stable enterotoxin A2 (ST-A2) in 12 strains, by the loss of a 60-MDa plasmid coding for heat-labile enterotoxin (LT) and ST-A2 in one strain, or by deletions of a segment of DNA encoding for ST-A2 in three strains. Among five CFA/II+ ETEC strains, the loss of CFA/II was associated with the loss of a plasmid of 75 MDa coding for LT and ST-A2 in three strains, with the loss of genes coding for LT and ST-A2 from a 68-MDa 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.

Specific DNA Fragments Coding for ST1 and LT1 Toxins, and K88 (F4) Adhesin in Enterotoxigenic Escherichia coli

“…The LT1 gene has also been reported to be located on plasmids of different molecular weights (So et al, 1978;HARNETT and GYLES, 1985;ECHEVERRIA et al, 1986;BROES et al, 1988). In this study, the LTI-containing plasmids ranged from 78MDa to 50MDa in molecular weight.…”

“…In this study, the ST1-gene appeared on two different plasmids among four different strains, but on an identical 8 MDa EcoR1-fragment. Other authors have reported the ST1 gene to be located on plasmids of different molecular weights (HARNETT and GYLES, 1985;ECHEVERRIA et al, 1986). The heterogeneity of the ST1 encoding plasmids with regard to molecular siz,e is probably accounted for by the transposability of the ST1 gene, as discussed by SO et al (1979).…”

“…This 140MDa plasmid is hardly visible on the photograph of the plasmid profile of strain 3844, and this may explain a possible undetectable hybridization result. ECHEVERRIA et al (1986) report, in their study of plasmids coding for colonization factor antigens I and I1 and enterotoxins from human E. coli isolates, a close structural association between the genes coding for these virulence properties. They suggest that the same environmental pressures involved in the selection of DNA sequences coding for ST1 b, might also have selected for colonization factors.…”

Molecular cloning and nucleotide sequence of the colonization factor antigen I gene of Escherichia coli

“…The attachment of the enterotoxigenic bacteria to the epithelial cells of the small intestine is mediated by fimbrial antigens, including colonization factor antigen I (CFA/I) (16,17), colonization factor antigen II (CFA/II) complex (12,41), colonization factor III (CFA/III) (8, 21), PCF8775 (CFA/IV) (29,43), and probably many others (42). The production of CFA/I is associated with a 60-megadalton plasmid in enterotoxigenic E. coli strains (10,17,27,39,46). The same plasmid in most instances also encodes a heat-stable enterotoxin (36,39).…”

“…The same plasmid in most instances also encodes a heat-stable enterotoxin (36,39). E. coli that has lost the 60-megadalton plasmid lacks CFA/I and does not cause diarrhea (10,17,27).…”