Systemic distribution of Staphylococcus aureus following intradermal footpad challenge of broilers

We conducted an experiment with broilers to determine if prior exposure to Staphylococcus aureus would facilitate the systemic infiltration of this pa thogen following intradermal footpad challenge with live S. aureus. Litter- raised broilers were sensitized at 3 and 4 wk of age with s.c. injections i n the neck with heat-killed S. aureus diluted in polyethylene glycol (PEC;) . Equal numbers of control birds were injected at the same times with PEG. At 7 wk of age, chicks previously sensitized to killed S. aureus or injecte d with PEG were injected intradermally in the right footpad with PBS or liv e S. aureus. The left footpads of all birds were injected with PBS. The dif ference in thickness between the right and left footpads was determined at 0, 24, and 48 h postchallenge. Blood, liver, spleen, lung, and synovial flu id were collected six times between 1 and 48 h postchallenge to determine t he recovery of S. aureus. Sensitized and nonsensitized birds showed footpad swelling following challenge with live S. aureus in the right footpad (P < 0.001). Injection of PBS did not induce footpad swelling. Birds injected i n the footpads with live S. aureus as compared to PBS had significantly hig her isolation rates of S. aureus in the spleen, liver, and blood; however, recovery of S. aureus from S. aureus-sensitized and PEG-injected birds was not significantly different. Time postchallenge (1, 3, 7, 11, 24, and 48 h) had no significant effect on the recovery of S. aureus. It was concluded t hat the intradermal challenge of the footpad with S. aureus resulted in sys temic infiltration of S. aureus into the spleen, liver, and blood. Prior ex posures to killed S. aureus as compared to PEG controls did not affect the systemic distribution of S. aureus.