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Page 9 of Attachment F 
Recombinant DNA and Genetic Experimentation 
APPENDIX II 
SUMMARY OF CONCLUSIONS FROM FEEDING 
AND MONITORING EXPERIMENTS 2 
M.H. Richmond, Bristol, UK 
1. E. coli K-12, even prototrophs, fed to man and livestock in high doses will 
generally survive about 4 days, although in a few individuals the organism can 
be detected by selective methods for nearly 2 weeks. The organism may multiply 
to a limited extent within 24-28 hours after administration but generally does 
not undergo more than a few doublings. 
2. If the E. coli K-12 that are fed carry a self-transferring plasmid that is 
de-repressed, the plasmid will be transmitted to the recipient flora. Trans- 
conjugants are found at a frequency of about 1 x 10 -1 ° of all E. coli shed per 
day. No evidence for the mobilization of non-transferable plasmids from E. coli 
K-12 has been found for naturally occurring F group or I group R plasmids. We 
think it unlikely that such transfer would occur with approved cloning vectors. 
This conclusion is supported by in vitro mobilization experiments. In vivo 
survival of EK2 strains and their potential transfer of either conjugative or 
non-con jugative plasmid must be considered to be below the current limits of 
experimental detection. 
3. E. coli K-12 strains which survive passage through the human or animal gut 
rarely show evidence of having acquired plasmids from the indigenous flora. In 
calf-feeding experiments, only 1 out of well over 10,000 K-12 strains which were 
screened had acquired colicinogeny . 
4. Over a period of 26 months in Bristol, 12 months in London and 12 months in 
Seattle involving 64 subjects, there was no evidence that laboratory workers, 
or members of their families, acquired either bacterial strains or plasmids 
that were employed in the laboratory. This was true even in a few individuals 
working in the laboratory who received short courses of antibiotic therapy. Moni- 
toring of the oropharynx failed to show any evidence of colonization by laboratory 
strains. Individuals with excessive facial hair likewise showed no evidence of 
carriage. In a few instances, individuals who had done routine experimental 
procedures (vortex mixing, or plating, etc.) showed transient numbers of E. coli 
K-12 on their laboratory garments, facial skin or hands. These organisms were 
few in number (4/cu mm ^) and disappeared within three hours. Simple washing with 
soap and water resulted in instantaneous loss of these organisms. No evidence 
whatsoever was found for even transient survival of E. coli EK2 derivatives. 
^The following Report was presented by M.H. Richmond to the Meeting of the 
Risk Assessment Subcommittee of COGENE which met at The Royal Society, London, 
on Friday, March 30th, 1979. The Report was compiled by Dr. Stanley Falkow on 
the basis of information provided by himself, by E.S. Anderson and by M.H. Richmond. 
The information contained in the Report represents the situation as it was at the 
end of October 1978, save that the data from Bristol have been updated to include 
information up to the end of 1978. 
[430] 
