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1 were the protective antigens, were transferred from 
2 Sh igella dysenter iae organisms into E. col i by Dr. Formol ,* 
3 and these E. col i carrying the Shigella genes were fed 
4 to adult volunteers in very high doses, as high as ten 
5 billion organisms, with proliferation, and there were 
6 no adverse effects whatsoever. 
7 In other studies, even more recently, we have 
g for a nunber of reasons attempted to determine the viru- 
9 lence properties that certain E. col i have — E. col i that 
10 cause traveler's diarrhea. Most of these studies were 
carried out, not by myself but by Drs. Hornick and DuPont 
12 in the sane division some years ago. 
13 In these studies, attempts were made to transfer 
14 the enterotoxin, the diarrhea-causing toxin, from E. col i 
15 that produced traveler's diarrhea into an E. col i that 
16 was cultured from a healthy individual, in the naive 
17 assumption that just transferring this one virulent 
18 property would result in a pathogen; and this organism 
19 with the transfer toxin was fed in high doses, and no 
20 1 llness occurred, and there was minimal proliferation. 
21 That was the first suggestion that we can't make a 
22 pathogen if we want to. 
23 Subsequently, additional virulence properties 
24 were put into E. col i . These were studies done about five 
25 or six years ago, and still there was no evidence that man 
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