Breast milk samples from three groups of Brazilian women were evaluated for their inhibitory effect on enteropathogenic Escherichia coli (EPEC) adhesion to HEp-2 cells: G1, mothers delivering preterm babies of appropriate birth weight (n = 12); G2, mothers delivering term babies of low birth weight (n = 11); G3, the control group, mothers delivering term babies of appropriate birth weight (n = 39). Colostrum samples were obtained at 48-72 h and milk samples on the 7th, 30th and 60th days after delivery. All samples showed strong inhibitory activity (66%-100%), without significant differences among the three groups and four periods. Total IgA and anti-EPEC IgA concentrations were significantly higher in colostrum than in milk samples in the three groups studied. The levels of colostral IgA and anti-EPEC IgA observed in G1 and G2 were significantly higher compared to the control group. Western blotting assays showed that individual samples as well as pools of colostrum or milk samples contain IgA antibodies to many EPEC outer membrane proteins. A 94 kDa band with molecular weight consistent with the EPEC adhesin named intimin; was recognized by all samples analysed. Bands of different molecular weight were also recognized by some samples of colostrum and milk, such as a band of approximately 18.4 kDa, with molecular weight equivalent to bundle-forming pilus subunits.
Conclusion: Our results suggest that colostrum and milk from mothers of premature and small-for-date term neonates are as effective in protecting the newborn against EPEC infections as those from mothers of term babies of appropriate birth weight.