Murine gastrointestinal tract as a portal of entry in experimental Pseudomonas aeruginosa infections.

Peroral administration of viable Pseudomonas aeruginosa into the stomach of mice resulted in an acute systemic infection, with death occurring within 72 h. One strain, ATCC 19660, a non-encapsulated form of P. aeruginosa, had a median lethal dose of 5.3 X 10(6) colony-forming units, whereas two encapsulated strains, ATCC 17933 and 17934, had median lethal dose values of 5.0 x 10(7) and 5.6 x 10(7) colony-forming units, respectively. Each strain required fewer organisms to establish a lethal infection via the stomach than by intravenous or intraperitoneal routes. The non-encapsulated strain, ATCC 19660, did not cause any diarrhea in the infected animals, whereas the two encapsulated strains, although less virulent, caused diarrhea when administered perorally. No signs of necrosis were noted within the gastrointestinal tract; however, hematogenous spread of the organism resulted in a vasculitis associated with the pulmonary vessels and bacterial invasion of the renal tissues. Treatment of animals with antineoplastic drugs 24 h before or simultaneously with peroral challenge resulted in an increased susceptibility to infection.