NOTICES 
27933 
them in gastight bags or by insuring ade- 
quate aeration following decontamination. 
/. Selecting Chemical Decontaminants for 
Research on Recombinant DNA Mole- 
cules 
No single chemical decontaminant or 
method will be effective or practical for all 
situations in which decontamination is re- 
quired. Selection of chemical decontaminants 
and procedures must be preceded by prac- 
tical consideration of the purposes for the 
decontamination and the interacting factors 
that will ultimately determine how that pur- 
pose is to be achieved. Selection of any given 
procedure will be influenced by the informa- 
tion derived from answers to the following 
questions : 
1. What is the target microorganism (s ) ? 
2. What decontaminants in what form are 
known to, or can be expected to, inactivate 
the target microorganisms(s) ? 
3. What degree of inactivation is required? 
4. In what menstruum is the microorga- 
nism suspended; i.e., simple or complex, on 
solid or porous surfaces, and/or airborne? 
5. What is the highest concentration of 
cells anticipated to be encountered? 
6. Can the decontaminant either as an 
aqueous solution, a vapor, or a gas reason- 
ably be expected to contact the microorgan- 
isms, and can effective duration of contact 
be maintained? 
7. What restrictions apply with respect to 
compatibility of materials? 
8. Does the anticipated use situation re- 
quire immediate availability of an effective 
concentration of the decontaminant or will 
sufficient time be available for preparation of 
the working concentration shortly before its 
anticipated use? 
The primary target of decontamination in 
- the infectious disease laboratory is the mi- 
croorganism under active investigation, 
Laboratory preparations or infectious agents 
usually have titers grossly in excess of those 
WfDOII 0 
normally observed in nature. The decontam- 
ination of these hlgh-tlter materials presents 
certain problems. Maintenance systems for 
bacteria or viruses are specifically selected to 
preserve viability of the agent. Agar, protei- 
naceous nutrients, and cellular materials can 
be extremely effective in physically retarding 
or chemically binding active moieties of 
chemical decontaminants. Such interferences 
with the desired action of decontaminants 
may require the use of decontaminant con- 
centrations and contaot times in excess of 
those shown to be effective in the test tube. 
Similarly, a major portion of decontaminant 
contact time required to achieve a given level 
of agent inactivation may be expended in 
inactivating a relatively small number of the 
more resistant members of the population. 
The current state of the art provides little 
information on which to prediot the prob- 
able virulence of these survivors. These prob- 
lems are, however, common to all potentially 
pathogenic agents and must always be con- 
sidered in selecting decontaminants and 
procedures for their use. 
Microorganisms exhibit a range of resist- 
ance to chemical decontaminants. In terms 
of practical decontamination, most vegeta- 
tive bacteria, fungi and lipid-containing 
viruses, are relatively susceptible to chemical 
decontamination. The non-lipid-containing 
viruses and bacteria with a waxy coating 
such as tubercle bacillus occupy a mid-range 
of resistance. Spore forms are the most 
resistant. 
A decontaminant selected on the basis of 
its effectiveness against microorganisms on 
any range of the resistance scale will be ef- 
fective against microorganisms lower on the 
scale. Therefore, if decontaminants that ef- 
fectively control spore forms are selected for 
routine laboratory decontamination, it can 
be assumed that any other microorganisms 
generated by laboratory operations, even in 
high concentrations, would also be inacti- 
vated. 
An additional area that must be consid- 
ered and for which there is little definitive 
information available Is the “inactivation" 
of nucleic acid. Nucleic acids often have bet- 
ter survival characteristics under adverse 
conditions than do the intact virions and 
cells from which they were derived. Strong 
oxidizers, strong acids and bases, and either 
gaseous or aqueous formaldehyde should re- 
act readily with nucleic acids. Their ability 
to destroy the nucleic acid being studied, 
however, should be confirmed in the experi- 
menter's laboratory. Because of innate dif- 
ferences in the chemistry of RNA and DNA 
the effectiveness of a decontaminant for one 
cannot be extrapolated to the other. For 
example, RNA molecules are susceptible to 
mild alkaline hydrolysis by virtue of the free 
hydroxyl group in the 2' position, whereas 
DNA molecules are not susceptible to mild 
alkaline hydrolysis. 
Table II summarizes pertinent characteris- 
tics and potential applications for several 
categories of chemical decontaminants most 
likely to be used in the biological laboratory. 
Practical concentrations and contact times 
that may differ markedly from the recom- 
mendations of manufacturers of proprietary 
products are suggested. It has been assumed 
that microorganisms will be afforded a high 
degree of potential protection by organic 
menstruums. It has not been assumed that 
a sterile state will result from application 
of the indicated concentrations and contact 
times. It should be emphasized that these 
data are only indicative of efficacy under 
artificial test conditions. The efficacy of any 
of the decontaminants should be conclu- 
sively determined by individual Investiga- 
tors. It is readily evident that each of the 
decontaminants has a range of advantages 
and disadvantages as well as a range of 
potential for inactivation of a diverse micro- 
flora. Equally evident is the need for com- 
promise as an alternative to maintaining a 
veritable “drug store” of decontaminants. 
TML£ II 
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VH. HOUSEKEEPING 
A. Introduction 
Well-defined housekeeping procedures and 
schedules are essential in reducing the risks 
of working with etiologic agents and in pro- 
tecting the integrity of the research program. 
This is particularly true In the biological 
laboratory operating under less than total 
containment concepts and in all areas used 
for the housing of animals, whether or not 
they have been intentionally infected. A well- 
conceived and well-executed housekeeping 
program limits physical clutter that could 
distract the attention and interfere with the 
activities of laboratory personnel at a critical 
moment in a potentially hazardous proce- 
dure, provides a work area that will not In 
itself be a source of physical injury or con- 
tamination, and provides an area that pro- 
motes the efficient use of decontaminants in 
the event of the inadvertent release of a 
harmful agent. Less immediately evident are 
the benefits of establishing, among person- 
nel of widely varying levels of education, an 
appreciation of the nature and sources of 
biological contamination. 
Housekeeping is an omnibus term that can 
be interpreted as broadly or as narrowly as 
one chooses. It can be seen that many of the 
FEDERAL REGISTER, VOL. 41, NO. 1 31— WEDNESDAY, JULY 7, 1976 
