Scratches as a component in the pathogenesis of avian cellulitis in broiler chickens exposed to cellulitis origin Escherichia coli isolates collectedfrom different regions of the US

Cellulitis was induced in broiler chickens in two experiments. Birds were p laced on used pine-shaving litter at day of hatch and raised to 28 days of age, at which time one-half the birds in each pen were scratched and the li tter was treated with either one of seven cellulitis origin Escherichia col i (collected from various locations in the US) or sterile saline. Although minor differences could be detected in the association of specific regional isolates with differing rates of cellulitis, all isolates were capable of inducing cellulitis in a preponderance of the scratched birds. These same i solates were not capable of producing cellulitis in birds that were not scr atched by design, confirming the importance of scratches in the pathogenesi s of cellulitis. Those birds in the unscratched groups placed on litter ino culated with either a cellulitis E. coli isolate (EC-AR1) or sterile saline that did develop cellulitis lesions showed the remnants of healed scratche s which had occurred naturally during the course of the growout, again prov iding evidence as to the importance of scratches in the development of cell ulitis.