EPIDEMIOLOGY
The characterization of a person’s infection as
laboratory acquired is usually retrospective
and is based on the assumption that the only
likely exposure occurred while the person was
in a laboratory. A trivial laboratory event may be
considered the possible exposure because
no other circumstance outside the laboratory could
account for infection (40, 44).
It is important, however, to appreciate that the
total laboratory testing cycle begins well
before the sample actually reaches the laboratory
(the preanalytic phase of laboratory
testing) and that exposures during the collection
and transport of the sample should also be
considered. In the past, infections acquired
during the collection of some samples were
included if it could be ascertained that the
collection was solely for the purpose of a
laboratory investigation. Infections experienced
by phlebotomists as a result of needlestick
injuries are now routinely considered
laboratory-acquired infections (27). In contrast,
phlebotomist infections (e.g., chicken pox)
acquired while collecting samples in patient
rooms are not included (24).
Although difficult to date precisely, the first
microbiology laboratories of Pasteur and Koch
were active by 1840 to 1860. The first report of a
laboratory-acquired infection,
Mediterranean fever, was in 1899 (7).
Various compilations of laboratory-acquired
infection have been published over the past 60
years (20, 32,
33,69, 73, 74). The first survey published, in 1953, was a
survey of 5,000
American laboratories by Sulkin and Pike. They
provided additional updates in 1961, 1965,
and 1976. They cited 3,921 laboratory infections
dating between 1930 and 1974, with a
mortality of 4.1%. Of note, 2,307 (58.8%) of the
infections were reported from research
facilities, 677 (17.3%) were from diagnostic
facilities, 134 (3.4%) were from the generation
of biological products (industry), and 106 (2.7%)
were from teaching facilities. The
remaining 697 (17.8%) infections had an
unspecified source.
Four series performed in the United Kingdom
between 1971 and 1991 revealed that within
clinical facilities, the majority of infections
were reported from workers in the microbiology
laboratory, followed by the autopsy service. Over
this 20-year period, the number of
infections reported dropped over 80%, from 104 to
only 17. While it is tempting to conclude
that laboratories are becoming safer, there are no
active monitoring programs in place to
capture the true number of accidents and
infections.
Compiled information tends to be limited to events
that are reported in the literature or in
specific databases. Thus, while uncommon community
infections, such as those associated
with Brucella species (1,
36a, 49a, 50a,55a, 73a, 76a), are commonly reported as
laboratory-acquired infections, very common
infections such asStaphylococcus
aureus (including methicillin-resistant S. aureus) infection are
rarely identified (70) as being
acquired in the laboratory. It is assumed that
even complete listings reflect an immeasurable
minority of infections that actually occur (69).
More recently, Internet-based discussion groups
have worked to create informationgathering
approaches (5,68).
While these newer surveys have challenges similar to those of
former retrospective compilations, they
demonstrate the potential for gathering important
information on laboratory safety and infection.
Two hundred cases of laboratory-acquired
infections with parasites resulting from laboratory
accidents, from 1929 through 1999, have been
published (40, 41). While the distribution of
cases changed from decade to decade, the number of
cases identified in each decade (19 to
28) remained relatively constant. Sharps-related
injuries (e.g., needles and glass) were
common factors, often associated with manipulation
of research animals and the production
of blood smears for malaria.
LABORATORY SAFETY AND PERSONAL ATTRIBUTES Back to
top
A matched case-control study of 33 laboratory
workers who experienced a laboratoryassociated
injury over a 2-year period was previously
described (57). No differences were
noted related to age, length of employment, years
of formal education, wearing of glasses,
use of prescription medications, or off-the-job
accidents or driving record. On the other
hand, the accident-involved persons were
significantly more likely to have had a laboratory
accident or laboratory infection prior to the
2-year study period and were significantly more
likely to have a low opinion of laboratory safety
programs. When the conditions surrounding
the accidents were examined, 36% occurred when the
employee was working too quickly,
either just before lunch or at the end of the day.
In 30% of accidents, the employee
acknowledged a breach in safety regulations. In
summary, in this study, attitudes and work
habits were important contributing factors to
laboratory accidents. While this study may
seem to be unduly dated, in today’s circumstances,
with increasing numbers of samples and
increasing complexity of tests, along with an
aging and shrinking workforce, rush, stress,
and awareness of risk continue to be relevant
issues (1a, 47).
In a study in which laboratory practices were
observed directly and then related to
laboratory environmental contamination with
hepatitis B virus (HBV), contamination was
strongly related to flawed technique and high
workload. Unsafe work practices were also
related, but to a lesser degree (32).
Over time, laboratorians have learned that even
conventionally accepted practices can result
in serious infection. Mouth pipetting, marking of
blood spots, transport of samples to the
laboratory in corked or sheathed sharps, recapping
of needles, eating, and smoking were all
practiced commonly at one time in properly run
medical laboratories. All of these practices
are now appreciated as risky and are prohibited.
Injuries with sharp objects continue to be
identified as an area of concern (20). Examination
of bacterial culture plates with an eyeglass or
sniffing plates to help identify organisms is
now controversial (3). Laboratory safety
requires diligent review and ongoing critique of
current conventional practice, as well as openness
to change when new risks are identified.
RISK-BASED CLASSIFICATION OF MICROORGANISMS Back
to top
As a foundation for determining environmental
requirements and best laboratory practices,
the international community has developed a common
risk-based classification of
microorganisms. Group 1 biological agents are
unlikely to cause human disease. Group 2
biological agents can cause human disease and
might be a hazard to workers but are
unlikely to spread to the community, and there is
usually effective prophylaxis or treatment
available. Group 3 biological agents cause severe
human disease and present a serious
hazard to workers. They may present a risk of
spreading to the community, but there is
usually effective prophylaxis or treatment
available. Group 4 biological agents cause severe
human disease and are a serious hazard to workers.
They may present a high risk of
spreading to the community, and there is usually
no effective prophylaxis or treatment
available. A partial list of microorganisms by category is shown
in Table 1.
SAFETY EQUIPMENT AND THE CLINICAL LABORATORY Back
to top
Splashguards
Splashguards made of clear glass or plastic
represent the minimum level of equipment for
protecting workers. They are more likely to
protect workers from gross splashes than from
aerosols. They can be an appropriate alternative
to biosafety cabinets for opening vacuum
blood tubes. They should be of sufficient size and
should be cleanable to remove the
occasional blood splatter. The effectiveness of
splashguards depends on appropriate
placement with respect to both work flow and
worker height. It is inappropriate to obscure
vision by using splashguards as a convenient
location for taped memos and procedures.
Biosafety Cabinets
Biosafety cabinets can protect the laboratory
worker and the laboratory environment from
splashes and aerosols and can also reduce the
opportunities for sample contamination
(73, 75). Biosafety cabinets are enclosed units with
various degrees of openness and access
and with control of exhausted air. Class 1
cabinets have an open front but work under
negative pressure, exhausting their air through a
HEPA filter. Exhausted air usually is
returned to the work area. Class 2 cabinets
increase the level of safety by including a HEPAfiltered
downward-flow air curtain designed to increase the
degree of separation between
room air and interior cabinet air. Class 2
cabinets may exhaust back to room air (class 2A) or
through an exhaust system to outside the building
environment (class 2B). Class 2B cabinets
can be subclassified further based on additional
features. Class 3 cabinets are completely
enclosed, providing gas-tight containment. They
are accessible only through front-end glove
ports. Class 3 cabinets provide the most suitable
containment for working with exotic
pathogens. Because class 1 and class 2A units
exhaust to the laboratory air, they are
unacceptable for use with volatile chemicals and
reagents. Biological safety cabinets cannot
be used as alternatives to chemical fume hoods.
All safety cabinets must be tested and certified
by a qualified person on a regular basis to
ensure that they maintain their required face
velocity and negative pressure.
Even properly maintained and certified cabinets
can be a hazard if equipment and materials
are placed improperly inside the cabinet.
Overcrowding the cabinet or stacking of equipment
against either the front or back grill will
disrupt the airflow, resulting in backwash out the
front of the unit (46). This can result in a
compound hazard because biological safety
cabinets are detrimental to worker dexterity,
making for a greater potential for accidents
(66).
Centrifuges
Although the safety centrifuge was first described
in 1975 (37), accidental contamination of
laboratory and personnel via centrifuges is
regularly reported (18, 34). While other
equipment may result in greater aerosol dispersal,
the frequency of use of centrifuges
increases their significance in accident risk
assessment (6). Accidents occur because of a lack
of tight seals on containers and rotors.
Centrifuges can be susceptible to contamination
because prolonged use without regular inspection
can lead to worn O-ring container seals
(38). Plastic centrifuge tubes can crack or distort
and result in increased risk (34). Accidents
can be avoided if centrifuges are used, cared for,
and maintained in a safe manner. Lids
must be closed at all times during operation. The
centrifuge should not be left until full
operating speed is attained and the machine is
running safely without vibration. If vibration
does occur, the centrifuge should be stopped
immediately and the load balances checked.
Swing-out buckets should be checked for clearance
and support. Ideally, rotors and cups
should be cleaned and disinfected with
noncorrosive cleaning solutions after each use. All
spills and breakage should be reported to the
laboratory safety officer and should be cleaned
immediately, after giving time for aerosols to
settle. In the context of quality control, a log
should be maintained and should include the rotor
serial number, speed (revolutions per
minute), duration of spin, times of use, and
operator’s name.
Chemical Fume Protection
A fume hood is a mechanically ventilated,
partially enclosed workspace where harmful
volatile chemicals and reagents can be handled
safely. The primary function of a fume hood
is to contain and remove gases and vapors.
Most fume hoods use ducts and a fan to ensure that
heat and airborne contaminants are
captured, transported out of the work area, and
eventually discharged into the atmosphere
outside the building. Chemical fume hoods differ
from biosafety cabinets in that they are
usually ducted. They must be constructed of
noncombustible materials, and they must also
be explosion proof.
Nonducted, or recirculating, fume hoods are of
limited use in the laboratory and should not
be considered acceptable substitutes for ducted
fume hoods for containment of volatile
chemicals (26).
Special fume hoods are designed to protect workers
from specific highly corrosive reagents
or chemicals, such as perchloric acid or
radioisotopes. Installation of fume hoods without
consideration of airflow and balance can result in
increased risk due to backwash and room
contamination (26).
As with biological safety cabinets, chemical fume
hoods require regular testing and
recertification. It is recommended that chemical
fume hoods be tested for both face velocity
and containment by use of the ASHRAE 110 tracer
gas test. Face velocity alone is not a valid
indication of containment (26).
Protection from Sharps
Scalpels, needles, broken glass, and other sharps
are commonly associated with wound
injuries and laboratory-acquired infections (2).
To the extent that it is possible, the use of
sharps should be eliminated or safety barriers
should be implemented (29, 70). Sharps may
be contaminated with infectious or cytotoxic
agents, or both. All sharps should be considered
potentially infectious and should be discarded in
safety containers. Sharps containers
minimize injuries and transmission of potentially
harmful agents, provided that they are
readily accessible and appropriately used.
Sharps containers used in medical laboratories
should be designed specifically for the
containment and disposal of needles, syringes with
needles, scalpel blades, clinical glass, and
other items capable of causing cuts or punctures (29,
71). If containers are not resistant to
penetration or compression, they pose a health
risk to those involved in their handling and
disposal.
The characteristics of well-designed containers
are that they are leakproof and puncture
resistant, do not degrade in autoclaves, either
require no assembly or are easy to assemble,
are appropriately labeled, and come in a variety
of sizes. Within this framework,
manufacturers can implement a variety of designs.
Sharps containers should be stable
enough to resist toppling over and durable enough
to withstand being dropped onto a hard
surface (13). Using locally available
tin cans or other containers in lieu of designed
containers is inappropriate, as they do not
address important aspects of containment.
Sharps containers must have a prominently
displayed universal biohazard symbol. In
addition, sharps containers intended to contain
sharps contaminated with cytotoxic
substances must display the cytotoxic hazard
symbol. The international color code is yellow
for biohazardous medical sharps and red for
cytotoxic medical sharps.
Containers should not be filled to more than
three-quarters of their maximum capacity to
avoid accidents from overfilling, and sharps
should never be forced into a container. Properly
designed containers have a designated fill line.
Most sharps containers are designed for a single
use only. Once filled, they are securely and
irreversibly closed for containment. Following
autoclave treatment, the containers should be
disposed of in accordance with local requirements.
Containers with cytotoxic sharps or
probable prion proteins should not be autoclaved
but rather require incineration.
To reduce the challenges associated with disposal
of single-use containers, reuse container
services can provide collection and transport to
an off-site location for safe, secure
reopening, emptying, and decontamination prior to
redistribution for reuse.
MEDICAL WASTE AS AN INFECTION HAZARD Back to top
Medical facilities generate large volumes of waste
that can be hazardous to workers and the
community (74). According to a recent
survey, most university hospitals in the United States
continue to use autoclaves to sterilize medical
waste, although many do not appear to
monitor autoclave effectiveness appropriately by
use of biological indicators (50).
Contractual arrangements with biomedical waste
management organizations may be an
economical or environmentally sound alternative. Alternatives
such as microwave
inactivation can be considered, with recognition
of the necessity of required rigorous
conditions (76). In some areas where
economic or environmental issues are of extreme
concern, solar disinfection (21)
of biomedical waste may be a viable consideration. In rare
circumstances in addressing zoonotic outbreaks,
and more commonly in resource-limited
regions, incineration of medical waste continues
to be performed, even though it has been
demonstrated to be harmful to health and the
environment (31, 38, 50, 74a).
SAFETY AS A QUALITY MANAGEMENT INITIATIVE Back to top
There is an increasing interest in medical
laboratory quality, safety, and risk, with a resulting
convergence of these issues (55).
International Organization for Standardization Technical
Committee 212 has developed documents to improve
the quality of medical laboratories,
including ISO 15189:2003 (Medical
Laboratories—Particular Requirements for Quality and
Competence) and ISO 15190:2003 (Medical Laboratories—Requirements for
Safety) (41b, 41c). In those countries where laboratories are
certified or accredited to the
requirements of the International Organization for
Standardization, these documents are
considered essential standards.
With respect to safety, ISO 15190:2003 addresses
management responsibility, safety
managers, safety manuals, safety programs,
education, training, competence, and audit and
review. It states that laboratory management is
respon sible for the safety of all employees
and visitors to the laboratory and that ultimate
responsibility rests with the laboratory
director. The laboratory must identify an
appropriately trained and experienced laboratory
safety officer to assist the laboratory director
and managers with safety issues. The
laboratory safety officer must have the authority
to stop activities that are deemed unsafe.
The laboratory safety officer is responsible for
designing and maintaining the laboratory
safety program and is responsible for monitoring
its effectiveness.
The elements of a laboratory safety program
include development of the laboratory safety
manual, safety audits and inspections (see Table 4 for audits required by ISO 15190:2003),
risk assessments, and the maintenance of records.
For further details, ISO 15190:2003 is
available through the International Organization
for Standardization website (www.iso.org)
HAND WASHING AND THE USE OF PERSONAL
PROTECTIVE EQUIPMENT Back to top
Hand Washing
Hand washing is the single most useful technique
to stop the transmission of microorganisms
and acquisition of infection in medical
laboratories (11). Hands can be contaminated during
sample collection, handling of sample containers,
handling of contaminated equipment, and
touching of sample storage units.
While contamination can be reduced by the use of
gloves, gloves alone are not completely
effective. Hand hygiene can be performed with
running water and either plain or
antimicrobial soaps. Nonmedicated detergent-based
soap products and water alone do not
disrupt the normal skin biota but can have some
effect on reduction of the transient hand
biota, including both bacteria and viruses (11,
72). The efficacy is directly related to the
duration of hand washing. Plain soaps, similar to
other products, can be associated with
detrimental effects, including skin drying and
irritation.
It is less clear whether soaps containing
antimicrobial products are essential for the vast
majority of hand-washing situations, even in the
microbiology laboratory. For example, hand
washing with plain soap is as efficacious as that
with antiseptic soap for
removing Clostridium difficile (36),
nonenveloped viruses, andBacillus anthracis (79).
For
short-term hand cleansing, the two product types
are equally efficacious for the removal of
common bacterial pathogens (9,
72).
Most laboratories will continue to see value in
regular use of antiseptic soaps. Selection of an
appropriate product for the laboratory depends
upon both the types of organisms processed
by the laboratory and issues such as fragrance,
consistency, and potential for irritation and
skin drying. Commonly used products contain
chlorhexidine, iodophors, triclosan, or related
compounds. Other ingredients, such as those
including tea tree oil, may be acceptable
alternatives (52).
Waterless alcohol-based products can be a rapid
and convenient alternative to conventional
hand washing, especially when a sink with running
water is not immediately accessible
(45, 72). When they are used correctly, alcohol-based
hand gels are as active as traditional
70% alcohol for removing methicillin-resistant S.
aureus, Serratia marcescens, and Candida
albicans from contaminated hands (81), but alcohol-based
products may have reduced
efficacy if hands are contaminated with
spore-forming organisms, including C. difficile and B.
anthracis (79), or with non enveloped viruses (72).
Alcohol-based products should not be
relied upon when hands are visibly soiled,
contaminated with proteinaceous materials, or
contaminated with materials that have a known high
microbial load.
It is common in many laboratories to place
alcohol- containing bottles by hand-washing
sinks. Others have noted that health care workers
are more compliant with hand care when
agents are close to the site of contamination (25).
Accordingly, laboratories might consider
having containers of alcohol-containing hand gel
closer to workstations.
Gloves
Gloves can provide an important barrier within the
laboratory, provided that they are used
appropriately. Clearly, gloves are essential to
prevent damage when hands are exposed to
heat, cold, and toxic materials. Insulated gloves
are essential for taking materials out of
−70°C freezers, exposure to liquid nitrogen, or
removing materials from autoclaves.
General purpose utility gloves (“kitchen” or
“rubber” gloves) provide ample protection for
cleaning biological spills, for general cleaning,
and for decontamination. Utility gloves can be
cleaned and reused, although they should be
examined regularly for cracks, tears, and
peeling. Damaged utility gloves should be
discarded. Utility gloves may be inappropriate for
handling chemical solvents and should not be used.
Chemical-resistant gloves should be
available in all laboratories that handle chemical
solvents and other toxic chemicals and
dyes.
The degree of protection that gloves can provide
depends upon many factors, including
composition, size, fit, grip, and thickness, all
of which can affect user dexterity. Latexcontaining
gloves may provide superior fine finger dexterity,
which could be associated with
fewer spills or accidents (65).
Disposable gloves of latex, vinyl, or nitrile can
provide an effective barrier, especially for
handling blood, body fluids, and excrement. This
is especially true because open abrasions
on hands can often go unnoticed (43).
In specific settings, gloves of increased length, to
elbow or shoulder, may be appropriate. Gloves are
easily torn. In-use durability studies
indicate that vinyl gloves may tear as often as
40% of the time, depending upon the
presence of powder and the length of the user’s
fingernails (43). Latex gloves are more
durable but may be associated with atopic
reactions.
It is critical for the user to remember that
handling equipment and materials with
contaminated gloves can cause considerable
environmental contamination. Gloves must be
removed either at the end of the task or when the
task is interrupted.
Regardless of the type of gloves and their composition,
it is essential that the user always
wash his or her hands as soon as gloves are
removed, either with running water and soap or,
in many settings, with alcohol-containing hand
hygiene products.
While it has become customary for phlebotomists to
wear gloves during specimen collection,
this may not be essential if the risk of exposure
to blood and body fluids is considered
sufficiently low and gloves of an appropriate size
or material are not readily available.
Regardless of whether gloves are worn or not
during the task of collection, hands should
always be cleansed immediately after the
completion of the task. Contaminated gloves often
result in contamination of equipment (53)
but can also contribute to transmission of serious
infection (59).
Disposable gloves do not provide significant
protection against needlestick injury. If sharps
exposure and the risk of injury are possible,
double gloving can provide some protection.
Cotton undergloves may provide more protection
than a second vinyl or latex glove. In the
morgue, use of chain mail gloves may be
appropriate.
Gloves provide an important protective barrier,
but they may also be a source of harm. Use
of vinyl, latex, or cotton undergloves can reduce
contact irritation noted with rubber gloves.
Excessive glove use can result in moisture damage
to skin (12, 19, 61). Surveys of dentists
wearing gloves for 6 h daily indicated that many
of them, especially young women with
preexisting eczema, suffered from glove
intolerance (80).
IMMUNIZATION Back to top
Immunization provides protection against some
laboratory-acquired infectious diseases but
should be considered secondary to mental alertness
and good laboratory practices.
Immunization may not prevent infection but can
protect against serious illness. All adults,
including pregnant women, should have a complete
primary immunization with tetanus and
diphtheria toxoids and should receive a booster
every 10 years (15).
Laboratory workers should receive annual influenza
immunizations. Similarly, all staff with
possible occupational exposure to human blood and
body fluids should receive the hepatitis B
vaccine. The value of meningococcal immunization
for laboratory workers has been discussed
previously (10, 14,
22). Cases of meningococcal illness possibly linked
to laboratory
exposure have been published, and it has been
recommended that microbiologists routinely
exposed to meningococci, especially aerosolized
organisms, should consider meningococcal
immunization. Laboratorians working with specific
pathogens and in specific situations should
consider additional immunizations, for example,
human diploid cell rabies vaccine, typhoid
vaccine, and vaccinia vaccine (48,
51).
In the past, Mycobacterium bovis BCG
vaccination has been considered valuable for health
care workers. However, it is no longer recommended
as a primary tuberculosis control
strategy because the protective efficacy of the
vaccine in health care workers is uncertain
and because immunization with BCG may cause
difficulty in the interpretation of tuberculin
skin test responses caused by true infections with
Mycobacterium tuberculosis. In laboratory
and other health care workers with positive
tuberculin skin tests, the new gamma interferon
release assays can help to differentiate likely
tuberculosis exposure (positive assay) from
BCG vaccination (negative assay).
LABORATORY-ACQUIRED HIV INFECTION, HEPATITIS B,
AND HEPATITIS C Back to top
Laboratory workers are at risk of blood-borne
infections such as hepatitis C virus (HCV),
HBV, and human immunodeficiency virus (HIV)
infections. However, the safeguards
introduced to medical laboratories have decreased
the risk to workers. According to the
Division of Health Care Quality Promotion, Centers
for Disease Control and Prevention
(http://www.cdc.gov/hai), between 1978 and December 2001, only 16
clinical laboratory
workers acquired HIV occupationally; 17 other
persons may have been infected in the
laboratory. Following a deep-tissue exposure
injury (e.g., needlestick), it is recommended
that workers consider postexposure prophylaxis (35),
even though this prophylaxis does not
always prevent HIV infection following an exposure
(31).
There is less information on the prevalence of
hepatitis C in health care workers, although it
is estimated by the National Center for Infectious
Diseases (28) that after needlestick or
sharps exposure to HCV-positive blood, about 2
(1.8%) health care workers of 100 will
become infected with HCV (range, 0% to 10%).
Following the introduction of the hepatitis B
vaccine in 1982, the incidence of HBV infection
was reduced by over 95% (70).
While blood-borne infection information may be
thought to be well established, recent
knowledge surveys of health care workers have
demonstrated that regular education
sessions to update existing staff and inform new
staff are required (67).
LABORATORY-ACQUIRED INFECTIONS AND EXTERNAL
QUALITY ASSESSMENT Back to top
Infections acquired in the clinical laboratory are
not always associated with clinical samples.
Documented clusters of bacterial infections have
been associated with samples sent to
laboratories for proficiency testing (8).
Contamination of other samples by quality control
organisms has also been documented (23),
although no in-laboratory infections resulted.
Regardless of the source, all viable
microorganisms processed in the clinical laboratory must
be handled with full awareness of appropriate
biosafety practices.
PRIONS Back to top
Samples from patients with Creutzfeldt-Jakob
disease (CJD) may be submitted to the
laboratory for investigation. To date, there are
no known cases of laboratory-acquired CJD,
and there is no evidence that laboratorians are at
increased risk of developing CJD. With that
being said, the progressive deteriorating nature
of CJD raises concerns for those handling
samples from patients with CJD, especially for
samples of neurological origin (64). This
represents a special problem in the medical
laboratory because of the difficulty in
inactivating the underlying prions.
Current precautions while handling tissue samples
require glove use. All tissue samples must
be discarded as medical waste. No special
precautions are required for disposal of body
fluids.
Equipment that has been exposed to CJD tissues
should either be discarded or, if tolerant to
heat, autoclaved at 134°C for 18 min (prevacuum
sterilizer) or at 121 to 132°C for 1 h
(gravity displacement sterilizer). Autoclaving in
water may be more effective than
autoclaving in its absence (33).
Equipment may also be soaked in 1 N NaOH for 1 h (33,
42).
Work surfaces should be cleaned with a 1:10
dilution of sodium hypochlorite.
Milder chemical treatments based upon combinations
of enzymes, including proteinase K and
pronase, in conjunction with detergents such as
alkaline cleaners or sodium dodecyl sulfate,
have been shown to experimentally reduce PrPSc
material to levels below detection and to
prevent infectivity. The advantages of these
methods are that they are described as being
inexpensive, noncorrosive, and nonhazardous to
staff (33, 42).
SARS CORONAVIRUS INFECTION AND OTHER SEVERE
VIRAL RESPIRATORY INFECTIONS Back to top
The 2002 outbreak of SARS associated with a
coronavirus reinforced international health
concerns about the hazards of aerosol spread of
communicable viruses. While laboratory
workers were at risk (56),
containment was readily addressable (4), and laboratory workers
were among those with the lowest rates of illness
or serological conversion (56). However,
microbiology and accessioning laboratory workers
receiving respiratory samples, especially
via vacuum tube delivery systems, were deemed to
be at increased risk. Since that time, the
concerns for similar events occurring with
influenza viruses, including H2N2 (17), H5N1 (30),
H7N7 (43), and novel H1N1 (35)
viruses, have pointed out the potential gaps in biosafety
protection for laboratory workers. Laboratories
equipped and designed to biosafety level 2
should use practices more consistent with those
for biosafety level 3, which require that all
samples be opened and handled only in a biosafety
cabinet (4). In addition, centrifugation of
samples should be performed only by using sealed
safety buckets that are opened within a
cabinet. Finally, personal protective equipment,
including M95 respirators, should be
considered for additional protection. Frequent
hand washing should be required (35), using
either soap and running water or alcohol-based
hand gels. While caution and reasonable
practices have been demonstrated to contain
outbreaks, effective influenza immunization is
most likely required in conjunction for optimal
protection.
SAFETY AND POINT-OF-CARE TESTING Back to top
Medical laboratories are responsible for all
aspects of laboratory testing throughout the total
testing cycle, even when the testing is performed
outside the laboratory itself. Increasingly,
medical laboratories are responsible for
point-of-care testing, such as blood glucose
monitoring, coagulation, and oxygenation. Despite
improvements in equipment and hygiene
protocols, cases of hepatitis B and C continue to
be associated with point-of-care devices.
Prevention of transmission requires strict
adherence to infection control protocols for
equipment cleaning. The international standard ISO
22870:2006 [lsqb]Point-of-Care Testing
(POCT)—Requirements for Quality and
Competence[rsqb] (41d)
provides guidance on quality
management for point-of-care testing.
TRANSPORTATION OF SAMPLES Back to top
Laboratories have a responsibility to prevent
exposure of individuals to infectious agents in
laboratory samples to the extent that is possible.
This responsibility includes samples being
transported to and from the laboratory. For local
transport within a clinic or hospital, the
laboratory should ensure that leakproof containers
are available, are transported in secure
outer packaging such as a sealable plastic bag,
and preferably are emblazoned with the
international biohazard label. For transport
outside the facility, especially by road, rail, ship,
or air, local and federal regulations apply. Even
for short distances, it is appropriate that
samples be transported in secure firm outer
containers with sufficient absorbent materials
inside, in case of a spill. In most jurisdictions,
transport of samples with infectious agents by
postal services is prohibited.
Air transport is under the authority of federal
regulations directed by the requirements of the
International Civil Aviation Organization, as
adopted by the International Air Transport
Association. The International Civil Aviation
Organization specifies packaging and labeling
requirements, including proper shipping name,
appropriate United Nations number (for
samples known to contain infectious agents based
on the source of the sample), and the
likely pathogens contained. Every laboratory that transports
samples is required to have at
least one person certified as knowledgeable with
respect to packaging and transport
requirements, including the completion of shipping
documents.
For additional information, direct reference can
be made to the International Civil Aviation
Organization’sTechnical Instructions for the
Safe Transport of Dangerous Goods by Air (41a)
or to federal requirements (58).
POSTEXPOSURE MANAGEMENT FOR ACCIDENTS
INVOLVING INFECTIOUS AGENTS Back to top
It is beyond the scope of this chapter to address
the specifics of medical management
following accidents that involve infectious
agents. However, it is important that the following
steps always be undertaken or considered. Every
accident or injury, including those that are
seemingly trivial (40), should be reported to
the appropriate safety officer or supervisor.
Scratches and puncture wounds should be cleaned
immediately. For some injuries, especially
those involving blood exposures, time may be a
critical factor (16). If it is deemed
appropriate to seek medical attention, it is
important to identify that the accident was
laboratory acquired. If the likely or probable
agent is known, bringing the microorganism
MSDS can be helpful and can save time. In research
or animal facilities, preparation of
information sheets on specific organisms and
availability of standardized investigation and
treatment protocols in the event of an accident can be invaluable.
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