Recommended biocontainment features for research and diagnostic facilities where animal pathogens are used. First International Veterinary Biosafety Workshop.

Recommendations are presented for the minimum structural components, special utilities, installations, and other design and operational features which define a microbiologically-secure animal containment facility. These biocontainment parameters are expected to enable the safe housing and handling of livestock and poultry infected with pathogenic agents. Physical testing and certification requirements for commissioning such facilities are described. Such a facility will minimise personnel exposure to infectious agents, limit cross-contamination between experiments, minimise horizontal transmission between research animals, and reduce the likelihood of pathogenic agents being released to the outside environment.

Microbiological hazard from the exhaust of a high-vacuum sterilizer.

Data are presented which show the potential for release of viable microorganisms into the atmosphere from high-vacuum steam sterilizers during the evacuation cycle preceding application of steam under pressure. Bacillus subtilis var. niger spores, Serratia marcescens cells, and T1 coliphage disseminated into the sterilizer chamber as small particles from liquid suspensions, and dried spores of B. subtilis var. niger distributed on bulk discard materials were recovered from the atmosphere around pipes venting steam from the steam ejectors used to create chamber vacuum. Evaluation of the hazard involved is discussed, and the design, fabrication, and installation of a valved filter system for preventing release of viable microorganisms are presented. The filtration system utilized an F-700 water-resistant filter and was shown to eliminate the release of viable airborne microorganisms from a high-vacuum sterilizer. A method is presented for determining size requirements for an atmospheric vent filter in relation to the volume of a sterilizer.

Biohazards assessment in large-scale zonal centrifugation.

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both the centrifuge chamber interior and rotor surfaces.

Paraformaldehyde for surface sterilization and detoxification.

Paraformaldehyde powder, depolymerized by heat, produced formaldehyde gas that was effective in sterilizing laboratory rooms, a mobile laboratory trailer, various surfaces, fiberglass filter medium, and specialized laboratory equipment. A sporulating and nonsporulating strain of bacteria, a virus, and a bacterial toxin were used as test agents. The dissemination procedures and equipment, the assay techniques, and the facilities and equipment sterilized were described.

Containment of microbial aerosols in a microbiological safety cabinet.

A microbiological safety cabinet was evaluated to determine conditions under which microorganisms might escape. Tests were conducted under three cabinet-closure conditions, various airflow velocities, and different laboratory operations, with 10(5), 1.1 x 10(5), and 10(6) microorganisms per cubic foot of cabinet space released per min for 5 min. The data revealed that (i) escape of a human infectious dose is possible when the cabinet is used with the glove panel off; (ii) the number of organisms that escaped from the cabinet increased with a decrease in air velocity; and (iii) an increase in the number of laboratory operations resulted in an increase in the number of organisms that escaped. Thus, when the glove panel was off, the cabinet was only safe for operations that released a small number of microorganisms into the cabinet, whereas the cabinet was safe for operations of significantly greater hazard when used with the glove panel on but with the gloves unattached.

Microbiological evaluation of a large-volume air incinerator.

Two semiportable metal air incinerators, each with a capacity of 1,000 to 2,200 standard ft(3) of air per min, were constructed to sterilize infectious aerosols created for investigative work in a microbiological laboratory. Each unit has about the same air-handling capacity as a conventional air incinerator with a brick stack but costs only about one-third as much. The units are unique in that the burner housing and combustion chamber are air-tight and utilize a portion of the contaminated air stream to support combustion of fuel oil. Operation is continuous. Aerosols of liquid and dry suspensions of Bacillus subtilis var. niger spores and dry vegetative cells of Serratia marcescens were disseminated into the two incinerators to determine the conditions required for sterilization of contaminated air. With the latter organisms (concentration 2.03 x 10(7) cells/ft(3) of air), a temperature of 525 F (274 C), measured at the firebox in front of the heat exchanger, was sufficient for sterilization. To sterilize 1.74 x 10(7) and 1.74 x 10(9) wet spores of B. subtilis per ft(3), the required temperature ranged from 525 to 675 F (274 to 357 C) and 625 to 700 F (329 to 371 C), respectively. Air-sterilization temperature varied with each incinerator. This was because of innate differences of fabrication, different spore concentrations, and use of one or two burners With dry B. subtilis spores (1.86 x 10(8)/ft(3)), a temperature of 700 F was required for sterilization. With dry spores, no difference was noted in the sterilization temperature for the two incinerators.

Micriobiological safety evaluation of an industrial refuse incinerator.

An industrial refuse incinerator was tested to determine minimal operating temperatures required to prevent release of viable microorganisms into the atmosphere. A liquid suspension of Bacillus subtilis var. niger spores was disseminated into the firebox as an aerosol, and dry spores mixed with animal bedding were dumped into the firebox. The minimal requirement for wet spores was 575 F (302 C) for the firebox air temperature and 385 F (196 C) for the firebrick refractory lining. When dry spores were used, these temperatures were 700 and 385 F (371 and 196 C), respectively.

Microbiological laboratory hazard of bearded men.

An investigation was conducted to evaluate the hypothesis that a bearded man subjects his family and friends to risk of infection if his beard is contaminated by infectious microorganisms while he is working in a microbiological laboratory. Bearded and unbearded men were tested with Serratia marcescens and Bacillus subtilis var. niger. Contact aerosol transmission from a contaminated beard on a mannequin to a suitable host was evaluated with both Newcastle disease virus and Clostridium botulinum toxin, type A. The experiments showed that beards retained microorganisms and toxin despite washing with soap and water. Although washing reduced the amount of virus or toxin, a sufficient amount remained to produce disease upon contact with a suitable host.