P fimbriae and aerobactin as intestinal colonization factors for Escherichia coli in Pakistani infants.

The carriage rate of a range of virulence genes was compared between resident and transient Escherichia coli strains obtained from the rectal flora of 22 home-delivered Pakistani infants 0-6 months old. Genes for the following virulence factors were assessed using multiplex PCR: P, type 1 and S fimbriae, three P fimbrial adhesin varieties, Dr haemagglutinin, K1 and K5 capsule, haemolysin and aerobactin. The E. coli strains examined here differed from those previously obtained from hosts in Western Europe in a lower prevalence of genes for P, S and type 1 fimbriae, K1 capsule and haemolysin. Nevertheless, genes for P fimbriae, the class II variety of papG adhesin, and aerobactin were significantly more common among resident than transient strains, as previously observed in a Swedish study. The results suggest that P fimbriae and aerobactin, previously implicated as virulence factors for urinary tract infection, might contribute to persistence of E. coli in the normal intestinal microflora.