Pathogen and Host Differences in Bacterial Adherence to Human Buccal Epithelial Cells in a Northeast Brazilian Community

The adherence of several strains of Escherichia coli to human buccal epithelial cells was studied, using cells obtained from five groups: healthy adults, healthy children, children with acute diarrhea, children with persistent diarrhea associated with cryptosporidial parasites, and children with noncryptosporidial persistent diarrhea. All groups lived or worked in an urban slum in northeastern Brazil. Samples of buccal epithelial cells from subjects in each of these groups were incubated with wild-type E. coli K-12 (strain C600), the enteroaggregative E. coli strains 17-2 and PDAS 30-5, CFA/II-positive E. coli 1392+ and its plasmid-cured derivative 1392-, and hydrophobic E. coli 132-3. Samples were evaluated microscopically to determine background contamination and the percentage of cells with more than 15% of their surface area obscured by adherent bacteria after incubation and washing. The assay was tested under field conditions and was shown to produce reliable and consistent results. Both enteroaggregative strains of E. coli were shown to adhere to a significantly higher percentage of all groups of human buccal epithelial cells than any of the other tested strains. In addition, buccal epithelial cells from children with nonparasitic persistent diarrhea showed substantially more bacterial adherence in both the native state and with all tested strains of E. coli than did cells from children with persistent cryptosporidial diarrhea or acute diarrhea or from healthy controls. This study provides evidence that enteroaggregative strains of E. coli demonstrate increased adherence to human buccal epithelial cells (as well as to cultured HEp-2 cells) and that buccal epithelial cells from children with noncryptosporidial persistent diarrhea appear to be more susceptible to bacterial adherence and colonization than buccal epithelial cells from control groups. These findings suggest that host differences as well as pathogen differences are important in the pathogenesis of persistent diarrhea and have implications for a potential role for buccal epithelial cell analysis in the diagnosis or risk stratification of children susceptible to noncryptosporidial persistent diarrhea.