Various doses of a virulent strain of S. flexneri 2a were injected into the cecal lumen of 20 cynomolgus monkeys.
Seven of 8 monkeys inoculated with 109 of the bacilli developed pronounced dysentery, 3 of 6 monkeys with 107 organisms and 1 of 6 monkeys with 105 developed dysentery, respectively. Clinical and pathological findings in these dysenteric cases were essentially the same as those in the oral administration with 109 of the bacilli. Thus, the method of direct injection of S. flexneri 2a into the cecal lumen proved useful to produce experimental dysentery even with relatively small doses such as 107 or 105 bacilli with which the authors could not produce dysentery by the oral route.
The possible mechanisms of the establishment of S. flexneri 2a infection in the alimentary tract of the monkeys are discussed from the viewpoint of the inoculum size and the inoculation route.
