Characterization of pathogenic Escherichia coli isolates from diarrheic one-week-old layer chicks

Abstract

Ninety (90) strains of Escherichia coli were isolated from intestine with fecal contents and liver of seven
days old commercial layers presenting diarrhea, and their pathogenicity was determined by in vivo
inoculation into the air sacs of day-old chicks. The test revealed 44 strains with high and intermediate
pathogenicity level that were analyzed by PCR for the presence of eight virulence genes, and their
serogroups were indentified using a set of anti-O antisera. Results demonstrate that these isolated
strains contained at least one of the eight genes searched and the majority of them (93.20%) possessed
gene iss. Seventeen (17) different genetic patterns have been detected with 15 having combinations of
two or more genes representing 70.45% of all analyzed strains. Eleven different serogroups were
identified, and the highest frequent was O8 (15.89%). Results demonstrate that strains that harbor
genes iss or astA and some that belonged to serogroups O133 and O142 may have been crucial for the
pathogenesis in the studied chicks, since several of these strains were pathogenic. The obtained
results demonstrated the importance of studies in E. coli of avian origin in regions engaged in intensive
poultry industry, aiming at evaluating the predominant strains and also acquiring preventive measures
to minimize losses due to colibacillosis.