MINUTES OF MEETING - March 6-7 
18 
Exotoxin A thus should not be included under the I-D-2 prohibition. 
Dr. Broadbent said he found Dr. Falkow's argument persuasive. Dr. Young 
agreed. He said that noncompromised individuals can be colonized by 
Pseudomonas aeruginosa without mortality. He added that Pseudanonas 
aeruginosa is a relatively nonpathogenic organism unlike Corynebacterium 
diptherfae or Clostridium botulinum in which a single toxin is the deter- 
minant of disease. Dr. Falkow said that while exotoxin A is an important 
virulence determinant of Pseudomonas aeruginosa , the symptoms experienced 
by infected individuals are not directly related to the toxin per se. 
Dr. Canpbell asked what degree of containment was used in working with 
Pseudomonas aeruginosa . Dr. Falkcw replied that Pseudomonas aeruginosa 
is a CDC Class 1 agent. 
Dr. Gottesman suggested the RAC first ascertain whether exotoxin A is a 
"toxin potent for vertebrates" in the context of the Guidelines. 
Mr. Thornton agreed; he added that the word "potent" should be defined. 
Dr. Falkow said that exotoxin A is several hundred fold less potent than 
botulinum and one-fiftieth as potent as diptheria toxin. 
Dr. Young moved that exotoxin A, under the Guidelines, not be considered 
a potent toxin similar to botulinum toxin. Dr. Canpbell noted that the 
effect of this motion would be to permit exotoxin A to be treated as any 
other gene of Pseudomonas aeruginosa . He said exotoxin A could thus be 
cloned into any organism on Sublist A, Appendix A, as an exempt experiment. 
Hie RAC accepted the motion by a vote of seven in favor, two opposed , and 
ten abstentions. 
Mr. Thornton suggested it would have been more appropriate to approve 
the cloning of the exotoxin A gene in Escherichia coli K-12 as requested, 
rather than approving the brqad motion passed. Dr. Canpbell agreed. 
Dr. Young moved to reconsider the former motion. Dr. Mason agreed, stating 
that the general issue of what constitutes a potent toxin under the Guide- 
lines should be examined. The motion to reconsider the previous motion was 
approved by a vote of fifteen in favor, none opposed, and two abstentions. 
Dr. Young then made a motion to approve the cloning of the Pseudcmonas 
aeruginosa exotoxin A gene in Escherichia coli K-12, under PI + EK1 condi- 
tions. The motion passed by a vote of fourteen in favor, none opposed, 
and three abstentions. 
Dr. Setlcw later appointed Drs. Broadbent, Maas, and Mason to examine the 
question of potency of a toxin under the Guidelines. 
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