ABSTRACT
Escherichia coli is recognized as a frequent cause of diarrhea in swine. The objective of this study was to phenotypically characterize the fimbrial types of 349 E. coli strains isolated from swine with diarrhea, in different age groups, through the microhemagglutination and seroagglutination tests and to determine the susceptibility profile in regard to the more common antimicrobials used on pig farms. Of the 159 strains that not agglutinate eritrocytes in the manose-resistant hemagglutination test (HAMR), 57 (35%) were positive for the expression of the fimbrial antigen F6, in the fast seroagglutination test carried out in plates. Considering the age group and the fimbrial phenotype, the potentially pathogenic serotypes of E. coli more prevalent until the third week of age were: F5 (K99), F6 (987P), F42 and F41 in, respectively, 29%, 23%, 11% and 10% of the strains. In piglets over 21 days old, fimbriae F4 (K88) predominated in 44.6% (58) of the strains. The animals were susceptible to strains containing F4, in all of the age groups, but with more frequency at more advanced ages, above 76 days. The largest resistance indexes were observed for oxytetracycline (84.0%), gentamicin (76.0%) and amoxicilin (72.0%). The smallest CIM 50 and 90 values were observed for ceftiofur.
KEY WORDS
Escherichia coli
; swine; fimbriae; CIM; multiple drug resistance