MINUTES OF MEETING - March 6-7 
6 
Mr. Thornton requested that the RAC Risk Assessment Subcommittee consider 
whether other areas of concern exist; e.g., should risk assessment be 
performed with other host-vector systems. Dr. Zaitlin asked that the 
Risk Assessment Subcommittee consider the desirability of initiating 
risk assessment experiments in the plant pathology area. 
Dr. Krause then introduced Dr. Stanley Falkow , from the University of 
Washington, who reported (tab 819, 858) on the unanimous recommendation 
of an NIAID Risk Assessment Working Group, which met on August 30, 1979, 
that NIAID not implement risk assessment protocols I and II developed 
from the proceedings of a Workshop held at Falmouth, Massachusetts, 
June 20-21, 1977. Protocol I, "Colonization and Transmission of Plasmids 
by Escherichia coli K-12 in the Gastrointestinal Tract of Humans," and 
protocol II, "Tests for Transmissibility of Plasmids of Escherichia coli 
K-12 and xl776 in Germ-Free Mice" had been developed to evaluate the 
probability that recombinant ENA, carried by an Escherichia coli K-12 
host-vector system, might be transferred to other members of the flora. 
Dr. Falkcw said the Risk Assessment Working Group, after evaluating the 
data generated by feeding Escherichia coli K-12 to over 60 different 
people, felt that these protocols would produce negative data. The 
Working Group, therefore, suggested that a "worst case" type of experiment 
be substituted for these two protocols. The alternative protocol would 
utilize instead of strain K-12 a "wild type" Escherichia coli strain, 
HS, which is known to be nonpathogenic and to colonize the majority of 
normal individuals who ingest it. The Working Group recommended that 
the cloning vehicle pBR325, coding for chloramphenicol resistance, be 
transformed into the HS strain, and that a wild type mobilizable plasmid 
such as ColEl carrying chloranphenicol resistance be used as a control. 
The group felt that this protocol would generate basic scientific inform- 
ation, i.e., mobilization frequencies in the gut, as well as provide 
risk assessment data for recombinant DNA. 
Dr. Falkow said that the NIAID Risk Assessment Working Group had in 
addition discussed the question of whether Escherichia coli K-12 can be 
converted into a pathogen. He said that no members of the Working Group, 
who collectively possess over 20 years of experience in attempting to 
make K-12 pathogenic, had succeeded in creating a pathogenic K-12. He 
described some of the attempts. 
Dr. Krimsky asked Dr. Falkow why K-12 is difficult to convert into a 
pathogen. Dr. Falkow stated that K-12, in adapting to the laboratory 
environment, was modified in major ways including modification in the 
principal outer membrane proteins. He noted that many Escherichia coli 
strains isolated from healthy individuals could not, anymore so than 
K-12, be converted into pathogens by laboratory manipulation. He discussed 
current epidemiological studies which suggest that a few widely dissemin- 
ated serotypes of Escherichia coli actually cause most cases of disease. 
[ 41 ] 
