THE UNIVERSITY OF ROCHESTER 
MEDICAL CENTER 
601 ELMWOOD AVENUE 
ROCHESTER, NEW YORK 14642 
AREA CODE 716 275-2871 
SCHOOL OF MEDICINE AND DENTISTRY • SCHOOL OF NURSING 
STRONG MEMORIAL HOSPITAL 
Richard B. Hornick, M.D. 
Dewey Professor of Medicine 
Physician-In-Chief 
November 2, 1979 
DEPARTMENT OF MEDICINE 
Donald Fredrickson, M. D. 
National Institutes of Health 
Bethesda, Maryland 20014 
Dear Dr. Fredrickson: 
I would like to lend my support to the proposal to downgrade the contain- 
ment levels for working with K12 E.col i bacteria in recombinant DNA work. The 
restrictions that this type of work be done without prior approval only when 
nonconjugative or nonmobilizing plasmids are being utilized and also that no 
mouth pipeting be allowed and in addition all material would have to be auto- 
claved appear to be most appropriate. It was my pleasure to serve for a short 
time on the RAC Committee and to have had the opportunity to listen to the 
debate regarding this change in containment levels. My own experience with 
a great deal of induced infections in volunteers with various types of bacteria 
including some K12 hybrids has obviously influenced my position on this change 
in the regulations. I feel quite comfortable, having had this experience, 
that the likelihood of human exposure could conceivably occur but the conse- 
quences of such exposure would pose no health hazard to the exposed individual. 
I would hope that the individuals who are overly concerned about the health 
hazard due to human exposure of a proposed accident would carefully review the 
literature on doses of pathogenic organisms required to cause disease and the 
accumulative evidence on the nonpathogenicity of even large doses of K12 E.col i . 
I would hope that this appraisal of these data would assure them of the safety 
of working with K12 organisms. 
In summary then, I would wholeheartedly agree with the recommendation to 
lower the containment levels of work with K12 with the provisos as outlined 
above. 
Sincerely yours, 
Richard B. Hornick, M. D. 
Chai rman 
Department of Medicine 
RBH :nv 
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