Experimental Enteritis in Cynomolgus Monkeys Produced by Intragastric Administration of Salmonella typhimurium

Abstract

To learn the minimum size of Salmonella organism required to develop gastroenteritis in humans, healthy cynomolgus monkeys were given intragastrically with various doses of a fimbriate (a wild-type) or a non-fimbriate of Salmonella typhimurium. Fourteen of 15 monkeys given 10⁷, 10⁵, or 10³ cells of a wild-type were infected. Among the monkeys infected, all 8 with 10⁷ cells, 4 of 5 with 10⁵ cells, and 2 of 6 with 10³ cells manifested enteritis. On the contrary, only 2 of 6 monkeys given 10⁷ or 10⁵ cells of a non-fimbriate were infected manifesting enteritis. Major symptom was watery diarrhea, but some cases excreted bloody mucous or loose stool. Abnormal stool was begun to excrete within the first a few days post administration in most of the cases. The watery diarrhea lasted for 2 to 3 weeks. The bloody mucous stool was excreted from the 2nd day to the 3rd day or from the 4th day to the 8th day. The loose stool was found on the 1st and 2nd days or the 2nd and 3rd days. At the onset of illness, abnormal stool contained 10³ to 10⁶ cells of the organism/g, and the number was increased during the course. At the autopsy conducted on the 2 monkeys excreted bloody mucous stool, gross change were found in the ileum and/or colon. The difference in the infectivity between the wild-type and non-fimbriate S. typhimurium is ascribed to the dierence in the ability of colonization in the intestine. It is suggested that an acute Salmonella gastroenteritis in Human is possibly caused by a smaller size of the organism than that proved by the experiment with volunteers and isolated strains.