Characterization of Escherichia coli Isolates from Peritonitis Lesions in Commercial Laying Hens

Abstract

<p>Five clinically normal chickens from three farms (farm A, farm B, and farm C), for a total of 15 clinically normal chickens, were examined bacteriologically. In a similar manner, five dead chickens with lesions of peritonitis from each of the same three commercial egg-laying operations were selected for bacterial culturing. <em>Escherichia coli</em> were isolated from the cloaca in 14 of 15 healthy chickens and from all 15 chickens with peritonitis. Oviducts of normal chickens did not contain <em>E. coli</em> (0/15) whereas oviducts from 13 of 15 hens with peritonitis were positive for this pathogen. No lesions and no <em>E. coli</em> (0/15) were found in the peritoneal cavity of healthy hens, but peritonitis lesions from 13 of 15 dead chickens yielded <em>E. coli</em>. On farm A and farm B, a flock consisted of all chickens within a single house and all chickens in each flock were of the same age and same genetic strain. In flock 1 from farm A, all five <em>E. coli</em> isolates from the oviduct and all five isolates from the peritoneal cavity were serogrouped as O78; contained the virulence genes <em>iroN</em>, <em>sitA</em>, <em>iutA</em>, <em>tsh</em>, and <em>iss</em>; and belonged to phylogenetic group A. In flock 2 from farm B, all four <em>E. coli</em> isolates from the oviduct and all four isolates from the peritoneal cavity were serogrouped as O111; contained virulence genes <em>iroN</em>, <em>sitA</em>, <em>iutA</em>, <em>traT</em>, <em>iss</em>, and <em>ompT</em>; and belonged to phylogenetic group D. These data suggest that all chickens with peritonitis in a single flock on farms A and B were likely infected by the same <em>E. coli</em> strain. <em>Escherichia coli</em> isolates from the magnum and peritoneum had the same serogroup, virulence genotype, and phylogenetic group, which is consistent with an ascending infection from the oviduct to the peritoneal cavity.</p>