Dr. Donald Frederickson 
APPENDIX M 
July 14, 1977 
The presentations dealing with the biology of E. coli covered a broad 
range of topics which can be briefly summarized under two major headings: 
1 . Conversion of E. coli K12 to an Epidemic Pathogen 
The group addressed itself to the question of whether there was any 
possibility of accidentally converting E. coli K12 into an epidemic strain. 
It was the unanimous conclusion of the participants that E. coli K12 is so 
severely enfeebled in many of the prime determinants of pathogenicity, 
virulence, and survival in nature, that it is incapable of being converted 
to an epidemic pathogen by DNA insertions. 
Or. Rolf Freter (Department of Microbiology, University of Michigan) 
emphasized the complexity of factors contributing to the pathogenicity of 
microorganisms. He noted that a pathogenic bacterium must possess a 
variety of factors which include: (1) survival in the environment so that 
it can spread from animal to animal; (2) multiplication within the host; 
(3) some mechanism for penetrating the skin or mucosal surfaces; 
(4) systematic spread within the host; (5) resistance to host defense 
mechanisms; and (6) production of a toxin or some other mechanism to 
damage the host to cause those symptoms associated with "disease". 
He added that if the critical constellation of virulence factors is absent 
or deficient, the bacterium will not be capable of causing disease. 
Several speakers noted, on the basis of their ov/n laboratory observations, 
that E. coli K12 is intrinsically impaired in most, if not all, of these 
properties. Moreover, the deliberate introduction of known virulence 
factors into E. coli K12 has failed to confer significant disease-provoking 
capacities . 
Other investigators described their unsuccessful attempts at long-term 
intestinal colonization in animals or man with E. coli K12. Dr. E. Anderson 
(Enteric Reference Laboratory, Public Health Laboratory Service, London) 
reported findings on the survival of E. coli K12 in the intestine of eight 
adult volunteers (three male and five female) who ingested this organism 
(10^ to 10^^ organisms) in 250 ml of milk. As in previously reported 
experiments of this type (Anderson, E.S. Nature 255 :502-504,1975), his 
new studies confirmed that the E. coli K12 were excreted in the feces for 
an average of four days, and occasionally up to six days. There was possibly 
some multiplication within the gut, but no colonization beyond six days. 
Dr. Rolf Freter reported on studies which showed that the intestine of 
germ-free mice could be colonized with E. coli K12. These experiments 
indicated that this organism, like other enteric bacteria, multiplied and 
colonized within this artificial intestinal environment which contained no 
competing bacteria. In other experiments involving the enfeebled EK2 
derivative of E. coli K12 known as xl776, Freter found that it was unable 
to become established in germ-f-ree mice. This EK2 strain is the only 
enteric bacterium he has encountered which cannot colonize the intestine 
of germ-free animals. 
Appendix M--3 
