eae-negative attaching and effacing Escherichia coli from piglets with diarrhea

One hundred and ninety strains of Escherichia toll that were isolated from pigs with diarrhea in the state of Sao Paulo, Brazil, and that were negativ e for enterotoxins and cytotoxins were investigated. Strains which adhered to HeLa cells were examined for fluorescence actin staining (FAS), the abil ity to induce attaching and effacing (A/E) lesions on HEp-2 cells detectabl e by transmission electron microscopy and the presence of eae gene sequence s detected by PCR. Intimin production was detected by western blot and sero grouping was performed. Forty-seven isolates adhered to HeLa cells in sever al patterns, but none adhered in a localized adherence pattern. However, se ven of the 47 adherent strains were positive for the FAS reaction, although the reactions were usually weak or atypical. One FAS-negative and three FA S-positive strains, which were examined for their ability to induce A/E les ions, were all positive. Subsequently, testing of these strains for the ene gene showed that they all lacked this gene. These findings, along with ear lier reports of eae-negative A/E E. coli, suggest that higher quantities of E. coli in this category might be detected if more reliance were placed on phenotypic tests rather than on gene detection tests alone. (C) 2001 Editi ons scientifiques et medicales Elsevier SAS.