Resident and transient Escherichia coli strains were identified
in the rectal flora of 22 Pakistani
infants followed from birth to 6 months of age. All strains were tested
for O-antigen
expression, adhesin specificity (P fimbriae, other mannose-resistant adhesins
or type 1 fimbriae)
and adherence to the colonic cell line HT-29. Resident strains displayed
higher mannose-
resistant adherence to HT-29 cells, and expressed P fimbriae (P=0·0036)
as well as other
mannose-resistant adhesins (P=0·012) more often than transient
strains. In strains acquired
during the first month of life, P fimbriae were 12 times more frequent
in resident than in
transient strains (P=0·0006). The O-antigen distribution
did not differ between resident and
transient strains, and none of the resident P-fimbriated strains belonged
to previously
recognized uropathogenic clones. The results suggest that adhesins mediating
adherence to
intestinal epithelial cells, especially P fimbriae, enhance the persistence
of E. coli in the large
intestine of infants.
Role of plasmids in virulence-associated attributes and in O-antigen expression in Shigella dysenteriae type 1 strains