P fimbriae and other adhesins enhance intestinal persistence of Escherichia coli in early infancy

Resident and transient Escherichia coil strains were identified in the rect al flora of 22 Pakistani infants followed from birth to 6 months of age. Al l strains were tested for O-antigen expression, adhesin specificity (P fimb riae, other mannose-resistant adhesins or type 1 fimbriae) and adherence to the colonic cell line HT-29. Resident strains displayed higher mannose-res istant adherence to HT-29 cells, and expressed P fimbriae (P = 0.0036) as w ell as other mannose-resistant adhesins (P = 0.012) more often than transie nt strains. In strains acquired during the first month of life, P fimbriae were 12 times more frequent in resident than in transient strains (P = 0.00 06). The O-antigen distribution did not differ between resident and transie nt strains, and none of the resident P-fimbriated strains belonged to previ ously recognized uropathogenic clones. The results suggest that adhesins me diating adherence to intestinal epithelial cells, especially P fimbriae, en hance the persistence of E. coil in the large intestine of infants.