Barrier Animal Housing

In the jargon of laboratory animal science, a "barrier facility" has come to be known as an animal housing system designed and managed to protect animals from undesirable microbes. In other words, "barrier" equates to "keep out." Until recently, the primary use of barriers was for the production of laboratory rodents; however, the need to maintain a similar level of barrier housing in the research environment extended the need for barrier housing to the research facility. The need has been expanded with the extensive use of immune-compromised animals and transgenic and knockout (TG/KO) mice.

The "barrier" may be at the cage level, the room level, at the level of an area within a facility, or the entire facility. For example, it is common to create a barrier in a conventional animal room using various types of cages and equipment, including microisolation caging systems, high-efficiency particulate air (HEPA) filtered mass air displacement racks, and flexible film isolators of the type used for maintaining germ-free animals. All of these approaches work reasonably well but are much more labor intensive to manage than a barrier designed as an area within a large animal facility or as

Figure 8.7 Schematic drawing of a containment area. This containment area was designed to provide maximum flexibility. It consists of six animal rooms. One is a standard animal room (B004) and five (B001, B003, B007, B008, and B017) are animal cubicle rooms, each of which is divided into four animal cubicles, an area for changing cages and conducting animal procedure in a biosafety cabinet, and an area for a sink and storage of feed containers and sanitation equipment and supplies. There are three entry and exit vestibules with interlocking doors. One vestibule (B010) enters into corridor B006, which along with animal rooms B001, B007, and B008, can be isolated from the rest of the containment area to serve as an Animal Biosafety Level 2 (ABSL-2) facility in which research staff enter and exit through vestibule B010. The second vestibule (B012) enters into corridor B014 that also may be entered from two private shower and locker rooms (B015 and B016). This is an ABSL-3 area. It includes three animal rooms (B003, B004, and B017), a laboratory (B013), a housekeeping closet (B005), and a bedding disposal room (B018). The bedding disposal room is for disposing of bedding soiled with hazardous chemicals or radioisotopes. The third vestibule is between the autoclave and the bedding disposal room. It enters the soiled side of the cage sanitation area so that cages contaminated with hazardous chemicals or radioisotopes can be taken directly to the cage and rack washer to be decontaminated without having to be being transported through corridors. The bulk autoclave is large enough to hold two racks. Cages contaminated with biohazards are autoclaved out of the containment area. The door between the ABSL-2 and ABSL-3 areas allows for the entire area to be operated as an ABSL-3 facility.

an entire facility. The primary difference is that with the room level barrier system, the cages and supplies are wrapped and autoclaved elsewhere in the facility before being transported to the animal rooms. In a barrier area of a larger facility, the cages and supplies are autoclaved into the barrier area; once inside the barrier, they are handled in a conventional manner, thus eliminating the need for wrapping and unwrapping. Some larger barrier facilities are designed with cage sanitation equipment inside the barrier, which offers the option of not autoclaving cages and relying on the level of sanitation provided by the cage washing equipment. Large rodent barriers may include a cage sanitation facility inside the barrier. This offers the option of relying on the level of sanitation provided by the cage washing equipment operating at a minimum temperature of 82.2°C (180°F) and not routinely autoclaving cages unless there is a disease outbreak. The use of irradiated feed and bedding also eliminates the need for autoclaving them.

Barrier facilities are designed and managed at various levels of microbiological control, which translates to the degree of control over how supplies and personnel enter the facility. The highest level barrier facilities may have one or more double-door pass-through autoclaves, preferably pit mounted, floor loading bulk autoclaves; one or more ventilated entry and exit vestibules with interlocking doors, where packaged sterile supplies and animals in filtered containers are passed into the barrier after having the exterior surface of the package chemically sanitized, or soiled equipment and trash are passed out of the barrier. Sometimes a pass-through dip tank filled with high-level disinfectants may be used to pass sterile items packaged in watertight containers into the barrier. Personnel may be required to shower and change clothing prior to entering the barrier, but more typically, at least in research barrier facilities, personnel enter through a vestibule with interlocking doors where they put on sterile outergarments over street clothes or uniforms along with head and shoe covers, a face mask, and gloves. Air showers using mass quantities of HEPA filter air may be added to a personnel entry vestibule.

Depending on the intended use of the barrier, space may be required inside the barrier for wet laboratories, animal procedure laboratories, TG/KO laboratories, specialized imaging equipment, irradiation equipment, etc. A research rodent barrier may require a quarantine area inside the barrier. This is especially important for a TG/KO facility, because quarantine is recommended for all foster mothers coming out of the TG/KO laboratory until the young are weaned and the mothers' health statuses are determined. Animal cubicles are useful for this purpose, even if the animals are housed in microisolation cages.

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