Colonization resistance of the digestive tract and the spread of bacteria to the lymphatic organs in mice.

After oral contamination of conventional mice with high doses of Escherichia coli, Klebsiella pneumoniae or Pseudomonas aeruginosa the contaminant was recovered in abnormally high concentrations from the duodenum and caecum during the first few days. In this initial colonization phase, evidence of spread was obtained by culturing the cervical and mesenteric lymph nodes and spleen. Longer after contamination the intestinal concentration decreased to normal and spread stopped. In orally antibiotic-treated mice, the situation seen during the initial colonization phase in conventional mice occurred after a much lower oral contamination dose and persisted during the entire observation period of 2 weeks.