1.1
Biological Safety
These guidelines advise SASVRC staff of the safety practices to be used
when handling biological specimens and reagents, particularly those that
may contain blood, blood products or body fluids of human origin. Infectious
agents of current concern to many persons, especially to health care workers
(HCW) and laboratory personnel, are the human immunodeficiency virus (HIV),
hepatitis B virus (HBV) and hepatitis C virus (HCV).
Risk
of Infection with a single needlestick injury from a patient known
to be infected.
Agent |
Risk |
Long-term
potential consequences following infection
|
HIV |
0.3%(1) |
The majority
develop severe and ultimately fatal illness
|
HBV |
3-3%(2)* |
A substantial
minoritydevelop serious long-term
illness which can result in fatal illness
|
HCV |
~3%
** |
A substantial
minority develop serious longterm illness which can result in
fatal illness
|
*It
is possible to differentiate between hepatitis B carriers who are relatively
infectious and those who represent a low potential for the transmission
of infection;
**after a contaminated needlestick injury from a patient
with antibodies to Hepatitis C.
Transmission
of these infections to another person in the workplace only occurs if
infectious material enters the body through the skin (via a break, cut
or on a sharp) or, less commonly, comes into contact with mucous membranes
such as the inside of the mouth or surface of the eyes. The risk of infection
in this setting relates to the dose of the infectious agent (concentration
of the agent in the blood or body fluid and volume of the fluid) which
accesses the blood stream of the individual.
Some
examples of levels of risk of infection are as follows:
- Negligible Risk
(non parenteral* exposure): blood or body fluid on intact skin. (*Parenteral
means taken into the body or administered in a manner other than through
the digestive tract).
- Lower Risk (possible
parenteral exposure): splash into eye or mouth with blood.
- Higher Risk
(definite parenteral exposure): injury with a contaminated needle
or instrument which penetrates the skin surface and draws blood.
- Highest Risk
(massive exposure): significant quantity of blood/body fluid (>1ml)
injected into the body such as can occur with unscreened blood transfusion
or injection of blood as the result of a needlestick injury or parenteral
exposure to laboratory specimens containing high titre of virus.
These
guidelines embody the principle that all blood, blood products, body fluids
and associated reagents should be regarded as infected with blood-borne
pathogens such as HIV, HBV and HCV, and that laboratory staff adhere rigorously
to protective measures which minimise exposure to blood-borne agents.
1.2
Disinfectants
1.2.1
Sodium hypochlorite
Effective against viable bacteria (except the tubercle bacillus) and
against viruses. It is the preferred disinfectant for HIV and hepatitis
viruses. Less effective against spores.
Prepare fresh daily. Use 0.5% hypochlorite for a spill or heavily contaminated
non-metallic surface. Do not use on metals or polycarbonate plastic
surfaces.
Ventilate well, and wear gloves, lab coat and safety glasses.
1.2.2
Ethanol (70% v/v)
Effective against viable bacteria and lipid-containing viruses. Not
effective against hepatitis C, some non-lipid containing viruses and
possibly cell-free, dried HIV (after 10 minutes).
70% ethanol is used on corrodable laboratory equipment or metal surfaces.
It is volatile, so repeated applications are needed. A contact time
of at least 20 minutes is necessary.
Ethanol is flammable, so do not use near flames or equipment likely
to cause sparks.
1.2.3
Glutaraldehyde (2%)
Most organisms are susceptible - immerse object for a minimum of 20
minutes.
Use of glutaraldehyde is discouraged because it is toxic.
1.2.4
Iodine
Effective against most organisms. Not used routinely as a disinfectant
in research laboratories. Iodine vapour is toxic and can be absorbed
through the skin.
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