ESCHERICHIA-COLI CELLULITIS - EXPERIMENTAL INFECTIONS IN BROILER-CHICKENS

The objectives of this study were to evaluate the role of trauma to th e skin in development of Escherichia coli cellulitis and to compare th e abilities of three cellulitis isolates (O78, O115, O21,83), one airs acculitis isolate (untypable) and one fecal isolate (O86) of E, coli t o induce cellulitis in broiler chickens. Forty-eight 4-week-old commer cial broiler chickens were housed in groups of six in eight battery ca ges. For five groups, the skin on the left side of the abdominal regio n of chickens was traumatized by scratching with a 22-gauge needle, th en contaminated with a swab dipped in a broth culture of one of the fi ve E, coli isolates. For chickens in the remaining three groups, an av ian cellulitis culture (O115, O21,83) or sterile broth was applied to intact skin. The experiment was duplicated. All birds were euthanatize d 10-13 days postinoculation. No lesion developed in chickens in which the skin had not been traumatized. Among the traumatized birds, cellu litis isolates induced characteristic lesions of cellulitis in 86% of the birds, whereas airsacculitis and fecal isolates induced lesions in 42% and 8% of birds, respectively. Severe or moderate gross pathologi c changes were found in 86% and microscopic pathologic changes were fo und in 88% of birds inoculated with cellulitis isolates; the correspon ding percentages for the airsacculitis isolate were 25% and 17%. This study demonstrated that trauma to the skin is necessary for initiating disease and that strains of E. coli of serotypes epidemiologically as sociated with cellulitis are highly virulent in experimental infection .