APPENDIX M 
Dr. Donald Frederickson 
July 14, 1977 
Dr. B. W. Snith (Houghton Poultry Research Station, Houghton, 
Huntingdon, England) described studies in which the virulence plasmids 
Ent, Hly and K99 were transferred from wild- type enterotoxigenic E. coli 
strains into E. coli K12. The wild-type strain carrying these plasmids 
uniformly caused severe diarrhea when fed by mouth to new-born calves. 
All of the E. coli K12 derivatives, with one possible exception, were 
non-pathogenic in this system; a single strain caused mild diarrhea in 
one of eight calves. 
Dr. S. B. Formal (Walter Reed Army Institute of Research) reported on 
human experiments carried out by his collaborator. Dr. R. B. Hornick (unable 
to attend meeting; Division of Infectious Diseases, University of Maryland 
Medical School) in which hybrids of E. coli K12 and Shigella flexneri , 
designed as vaccine strains, were fed to human volunteers at doses of 
The hybrid strain expressed the 0 antigens of Shigella flexneri. 
The results were that the hybrid E. coli K12-Shigella caused no disease* 
the strain was cleared from the intestinal tract in five days or less, and 
there was no stimulation of serum antibody production to Shigella antigens. 
This indicates that the organism failed to colonize the bowel. In contrast, 
most volunteers receiving comparable numbers of a wild- type E. coli strain 
excreted the organisms from 10 to 105 days, indicating that the wild-type 
E. coli implanted and reproduced in the gut. 
Dr. E. Gangerosa (Enteric Section, National Communicable Disease 
Center, Atlanta, Georgia) and Dr. R. B. Sack (Department of Medicine, 
Johns Hopkins University) discussed the epidemiology of intestinal diseases 
caused by E. coli . They pointed out that these organisms are generally 
more benign than other bacterial pathogens. The establishment of secondary 
infections and epidemic spread are difficult to achieve, and would occur 
only in a grossly unsanitary environment. 
At the conclusion of this session, I, acting as Chairman, asked if 
there v;as a consensus agreement with the concept that E. coli K12 could 
not be inadvertantly converted to an epidemic pathogen by inserted DNA 
molecules. Indeed, there was unanimous agreement, and Dr. H. W. Smith 
carried the assertion one step further, saying that, in his opinion, not 
only would this not happen inadvertantly, but even deliberate attempts to 
produce an epidemic pathogen would require twenty years of full-time effort. 
2. Transmission of DNA from E. coli K12 to Other Organisms 
The group discussed at length the possibility of accidental transmission 
of cloned DNA from E. coli K12 vectors to other organisms within the intestinal 
tract. Dr. E. S. Anderson reported on experiments in which E. coli K12 
containing a non-conjugative plasmid element was fed to human volunteers. 
As noted in the previous section, the E. coli K12 could not be found in the 
feces after six days; furthermore, no transfer of the plasmid could be 
detected when bacteria from the feces of the volunteers were examined. 
Appendix M--4 
