Concepts of Biosafety (Русский)
Biosafety and Public Health
Infectious diseases today ignore geographic and political boundaries, and constitute a global threat that puts every nation and every person at risk. In this age of expanding travel and international trade, infectious microbes are transported across borders every day, carried by infected people, animals, insects and goods. This has caused a growing concern for the authorities in the region and around the world as these outbreaks are often difficult to control and the spread across borders within the region and around the world can be so rapid that countries affected are unable to respond adequately. Such grave consequences can lead to lost lives, travel restrictions, the culling of animals to prevent further spread and disastrous economic damages.
To respond to outbreaks effectively, early isolation and identification of the causative agents become a requirement of paramount importance in the design and implementation of an effective disease control program. Additionally, bioterrorism attacks involving highly dangerous pathogens can lead to outbreaks of disease that quickly spread across borders. States lacking adequate laboratory capacity for preparedness and response to emerging diseases and bioterrorism events represent a real threat to global health and security. Laboratory containment capacity and biosafety are thus part of the important technical capabilities required by countries for effective public health security.
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Biosafety Rational
Individuals who work in a laboratory that handles infectious substances are at risk of exposure to the substances they handle. Laboratory-acquired infections (LAIs) are not uncommon — over 5,000 cases and 190 deaths had been reported up to 1999, although these figures are believed to be a significant underestimate because of underreporting. Additionally, only about 20% of infections can be attributed to any known, single exposure event.
There are a number of ways in which infectious substances can enter the body and cause infection, including ingestion, inhalation, or contact with mucous membranes, including conjunctivae (transfer of microorganisms to the eyes by contaminated hands), or with non-intact skin. The types of events that can lead to an infection include the following: exposure to infectious aerosols; spills and splashes; accidental needlestick injuries; cuts from sharp objects and broken glass; bites and scratches from animals or ectoparasites; oral pipetting (which is prohibited); centrifuge accidents; secondary spread of infectious materials to nonlaboratory areas. Exposure to aerosols may be the greatest biohazard facing laboratory workers. Aerosols can present a risk in terms of inhalation, ingestion, mucous membrane contact, etc.
The term biosafety is used to describe safe methods for handling infectious materials in the laboratory. The purpose of biosafety is to reduce or eliminate exposure of laboratory workers, other persons, and the outside environment to potentially infectious agents. Biosafety is provided by a combination of operational practices, containment equipment and facility design. The most important aspects of biosafety are the practices and procedures used by trained laboratory staff. The World Health Organization's Laboratory Biosafety Manual states that "no biosafety cabinet or other facility or procedure alone guarantees safety unless the users operate safe techniques based on informed understanding." It is the responsibility of everyone, including managers and laboratory workers, to use to perform their work in a safe manner.
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General Principles
Classification of organisms according to risk group has traditionally been used to categorize the relative hazards of infective organisms. The factors used to determine which risk group an organism falls into is based upon the particular characteristics of the organism, such as:
- pathogenicity
- infectious dose
- mode of transmission
- host range
- availability of effective preventive measures
- availability of effective treatment.
These classifications presume ordinary circumstances in the research laboratory or growth in small volumes for diagnostic and experimental purposes. Four levels of risk have been defined by the World Health Organization as follows.
Risk Group 1 (low individual and community risk)
Any biological agent that is unlikely to cause disease in healthy workers or animals.
Risk Group 2 (moderate individual risk, low community risk)
Any pathogen that can cause human disease but, under normal circumstances, is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures rarely cause infection leading to serious disease; effective treatment and preventive measures are available, and the risk of spread is limited.
Risk Group 3 (high individual risk, low community risk)
Any pathogen that usually causes serious human disease or can result in serious economic consequences but does not ordinarily spread by casual contact from one individual to another, or that causes diseases treatable by antimicrobial or antiparasitic agents.
Risk Group 4 (high individual risk, high community risk)
Any pathogen that usually produces very serious human disease, often untreatable, and may be readily transmitted from one individual to another, or from animal to human or vice-versa, directly or indirectly, or by casual contact.
Classification of organisms according to risk group is not meant to establish the actual handling of biological hazards in the laboratory setting. For example, the risk group system does not take into account the procedures that are to be employed during the manipulation of a particular organism. Biosafety levels are selected to provide the end-user with a description of the minimum containment required for handling the organism safely in a laboratory setting. In addition to the inherent characteristics of each organism, the containment system includes the engineering, operational, technical and physical requirements for manipulating a particular pathogen. These biosafety levels are applicable to facilities such as diagnostic, research, clinical, teaching and production facilities that are working at a laboratory scale
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Four biosafety levels are described as follows:
Biosafety Level 1 (BSL1)
BSL1 requires no special design features beyond those suitable for a well-designed and functional laboratory. Biological safety cabinets (BSCs) are not required. Work may be done on an open bench top, and containment is achieved through the use of practices normally employed in a basic microbiology laboratory.
Biosafety Level 2 (BSL2)
The primary exposure hazards associated with organisms requiring BSL2 are through the ingestion, inoculation and mucous membrane route. Agents requiring BSL2 facilities are not generally transmitted by airborne routes, but care must be taken to avoid the generation of aerosols (aerosols can settle on bench tops and become an ingestion hazard through contamination of the hands) or splashes. Primary containment devices such as BSCs and centrifuges with sealed rotors or safety cups are to be used as well as appropriate personal protective equipment (i.e., gloves, laboratory coats, protective eyewear). As well, environmental contamination must be minimized by the use of handwashing sinks and decontamination facilities (autoclaves).
Biosafety Level 3 (BSL3)
These agents may be transmitted by the airborne route, often have a low infectious dose to produce effects and can cause serious or life-threatening disease. BSL3 emphasizes additional primary and secondary barriers to minimize the release of infectious organisms into the immediate laboratory and the environment. Additional features to prevent transmission of BSL3 organisms are appropriate respiratory protection, HEPA filtration of exhausted laboratory air and strictly controlled laboratory access.
Biosafety Level 4 (BSL4)
These agents have the potential for aerosol transmission, often have a low infectious dose and produce very serious and often fatal disease; there is generally no treatment or vaccine available. This level of containment represents an isolated unit, functionally and, when necessary, structurally independent of other areas. BSL4 emphasizes maximum containment of the infectious agent by complete sealing of the facility perimeter with confirmation by pressure decay testing; isolation of the researcher from the pathogen by his or her containment in a positive pressure suit or containment of the pathogen in a Class III BSC line; and decontamination of air and other effluents produced in the facility.
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Risk Assessment
Risk assessment is a critical step in the selection of an appropriate containment level for the microbiological work to be carried out. A detailed local risk assessment should be conducted to determine whether work requires containment level 1, 2, 3 or 4 facilities and operational practices. In addition to the inherent characteristics of the biological agent, the following factors associated with the laboratory operation should also be examined:
- potential for aerosol generation
- quantity
- concentration
- agent stability in the environment (inherent biological decay rate)
- type of work proposed (e.g., in vitro , in vivo , aerosol challenge studies)
- use of recombinant organisms
If a particular procedure, such as preliminary identification, poses a lower hazard than manipulation of a live culture, then a lower containment level may be appropriate. For example, primary diagnostic tests for HIV may be done in a containment level 2 physical but growing and manipulating a culture of HIV may require a containment level 3 facility. On the other hand, an increase in containment may be required if the local risk assessment indicates that the procedures pose a higher risk. For example, a risk assessment may indicate that a procedure involving cultures of MDRTB (multi-drug resistant Mycobacterium tuberculosis ) is more appropriately carried out at containment level 3 while diagnostic activities involving smear microscopy may only require containment level 2.
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Emerging Challenges
In today's new reality the considerations that guide what we do on a daily basis have changed dramatically, and the biological safety profession is no exception to this. Not only does the biosafety professional have to concern him/herself with keeping potentially dangerous pathogens in an environment that is safe and contained, but they now have to equally concern themselves with keeping potentially dangerous individuals out. These concerns can be further complicated by shrinking budgets, limited resources, and the threat of a potential pandemic looming around the corner. The responsibilities of today's biosafety professional require them to be all at once a scientist, an engineer, a security expert, and a teacher. In order for today's biosfety professionals to efficiently achieve their objectives it will be crucial that they develop and/or participate in an interrelated framework for responding to their new challenges. This should included: a highly focused and well-coordinated national, regional and international response; a high degree of collaboration among biosafety organizations on emerging issues; a global biosafety capacity; integration into global public health security; bringing forward innovative ideas, and finally working together.
Facing the challenges of an evolving world, biosafety professionals have had to become flexible and adaptable to the increasing demands on their profession. Multidisciplinary and integrated networks are now fundamental requirements of the profession. Building a global biosecurity capacity through an integrated network is an important concept that is driving biosafety professionals as they work to minimize the likelihood of a bioterrorist event and prepare for the eventuality of the next pandemic or emerging infections disease. As the biosafey profession continues to respond to new challenges it will be crucial to build upon the interrelated framework it has established between its regional, national, and international organizations, as well as other agencies, and work together to come up with innovative ideas and solutions to the evolving challenges it will continue to face.
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