Reaction of the avian respiratory system to intratracheally administered avirulent Salmonella typhimurium.

Chickens were inoculated intratracheally (IT) with the SR-11 Salmonella typhimurium deletion mutant x4062 strain. Data collected for 8 days postinoculation (PI) were: signs of respiratory and gastrointestinal disease; histological lesions; the influx, phagocytic proportion, and phagocytic capacity of avian respiratory phagocytes (ARPs); and the proportion of granulocytes vs. macrophages in the lung tissues and lavage fluids of the lungs and air sacs. S. typhimurium-inoculated chickens had no clinical signs of gastrointestinal or respiratory disease but had various degrees of inflammatory changes in the lungs. At 5 hr PI, S. typhimurium-inoculated chickens had approximately 53-fold more ARPs than mock-inoculated controls. Between 26 hr and 8 days PI, the number of ARPs from S. typhimurium-inoculated birds was not significantly higher than the number from the mock-inoculated controls. Flow cytometric analysis of ARPs demonstrated that the proportion of phagocytic ARPs and the phagocytic capacity of ARPs from S. typhimurium-inoculated chickens were significantly higher between 5 and 26 hr PI than those of the ARPs from mock-inoculated chickens. Kinetic changes over 8 days in the granulocyte/macrophage ratios in the lavage fluids, as compared with kinetic changes in the lung tissues, suggested that the granulocytes generally represent a much higher proportion of the ARPs, and egress earlier and in much larger numbers from the tissues to the lumen of lungs and air sacs than do macrophages.