Promoting effect of intestinal Pseudomonas aeruginosa on gastric tumorigenesis in rats with N-methyl-N'-nitro-N-nitrosoguanidine.

The effect of Pseudomonas aeruginosa colonizing in the gut on the development of gastrointestinal tumors was studied in rats treated orally with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The animals were inoculated with or accidentally colonized by P. aeruginosa after MNNG treatment. In 3 serial experiments, P. aeruginosa-positive, MNNG-treated rats consistently showed a significantly higher incidence of gastric tumors than P. aeruginosa-negative, MNNG-treated animals. The total incidence of gastric tumors was 40% (34/86) in the former, and only 11% (7/61) in the latter. The development of tumors in the small intestine was not likely to be influenced by P. aeruginosa colonization. It is concluded that P. aeruginosa in the gut plays a promoting role in gastric tumorigenesis in rats orally administered with MNNG.