Influence of Mycoplasma gallisepticum, infectious bronchitis, and cyclophosphamide on chickens protected by native intestinal microflora against Salmonella typhimurium or Escherichia coli.

Chickens that have considerable resistance to Salmonella typhimurium or Escherichia coli infection by early development of a native intestinal microflora shed these bacteria following aerosol exposure to Mycoplasma gallisepticum and/or infectious bronchitis virus. Administration of cyclophosphamide to similarly treated chickens induced slight shedding of these bacteria, and the combination of cyclophosphamide and respiratory agents magnified the shedding rate. These agents also influenced the isolation rate of E. coli and S. typhimurium from the trachea and air sacs.