27 
( i i ) Prokaryotic DNA recombinants 
2 
Prokaryotes that exchange oenetic information with E. coli - 
"he level of physical containment is directly determined by the rule 
of the most dangerous component (see introduction to Section III). 
Thus PI conditions can be used for DNAs from those bacteria in Class 1 
of ref. 5 ( Agents of no or minimal hazard ") which naturally ex- 
change genes with E_. col i ; and P2 conditions should be used for such 
bacteria if they fall in Class 2 of ref. 5 ("Agents of ordinary potential 
^.azard ), or are plant pathogens. EK1 host-vectors can be used for 
all experiments requiring only PI physical containment; in fact, ex- 
peri-ents in this category can be performed with E_. coli K-12 vectors 
exhibiting a lesser containment (e.g., conjugative plasmids) than EK1 
vectors. Experiments with DNA from species requiring P2 physical con- 
*ai r ~srt which are of 'ow pathogenicity (for example, enteropathogenic 
— — ' > Sa ~o r e 'a typhimjrium , and Klebsiella pneumoniae ) 
car use iKl '’ost-vectors , but those of moderate pathogenicity (for 
ex -~- :e > Sa'-one^a typhi , Shigella dysenteriae type I, and Vibrio 
c r c erae . should use EK2 host-vectors.' 
2 
Defined as observable under optimal laboratory conditions by transformation, 
transduction, phage infection and or conjugation with transfer of phage, plasmid 
and/or chromosomal genetic information. 
3 
I.-c “ aCl -eria vnich constitute C^ass 2 of ref. 5 ("Agents of ordinary potential 
- • • • • ) -=j.resent a broad spectrum of etiologic agents which possess dif- 
ferent levels ot virulence and degrees of communicability. We think it appro- 
priate tor our specific purpose to further subdivide the agents of Class 2 into 
: : ' :se " hlch ve believe to be of relatively low pathogenicity and those which are 
moderately pathogenic. The several specific examples given may suffice to 
E-iustrate the principle. The Committee has asked the Center for Disease Control 
r T r ^~ w . ~ ^ p-i.ete lis l or Class 2 agents subdivided into low and moderate 
pathogenicity that could be distributed to interested parties. 
[ 98 ] 
