A single strain of Staphylococcus aureus was used to study the pathogenesis of osteomyelitis in chickens. The disease was consistently reproduced in 6-week-old broiler chickens when 1 X 10(5) or more organisms were given intravenously. Severe feed restriction, debeaking, and single or multiple injections of corticosteroids delayed the appearance and decreased the severity of lesions due to staphylococcal infection. This increased resistance was associated with increased numbers of circulating heterophils and monocytes. No correlation between the presence of tibial dyschondroplasia and osteomyelitis was found.

Groups of 6-week-old broiler chickens were exposed to Staphylococcus aureus by aerosol, intratracheal or intravenous (control) inoculation. No lesions were produced by aerosol. A single dose of up to 5 X 10(10) organisms given intratracheally failed to produce any lesions. Single or repeated doses of 5 X 10(11) organisms given intratracheally resulted in osteomyelitis in a low proportion of chickens.

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