Effect of microwave radiation, pasteurization and lyophilization on the ability of human milk to inhibit Escherichia coli adherence to HEp-2 cells.

The effect of different physical treatments on the ability of colostrum and human milk to inhibit the adherence of enteropathogenic Escherichia coli (EPEC) to human epithelial cells was studied. Pools of colostrum and milk were submitted to microwave radiation, pasteurization or lyophilization, and then tested for the ability to inhibit the adherence of EPEC O111:H- to HEp-2 cells. The inhibitory effect of untreated colostrum and human milk on localized adherence was not significantly modified after exposure to any treatment. The total protein values of colostrum and milk were maintained, but IgA concentration and colostral anti-EPEC IgA were reduced after pasteurization. Nevertheless, the remaining IgA was sufficient to be effective in adhesion inhibition assay. Western blotting assays carried out with EPEC antigens showed that the treated and untreated pools recognize a 94-kDa outer-membrane protein which molecular weight is compatible with intimin, an EPEC adhesin related to bacterial attachment to epithelial cells. These results suggest that the protection of colostrum and milk to infantile diarrhoea due to EPEC remains unalterable after the physical treatments studied.