Medical Applications of Dust-free Rooms. III. Use in an Animal Care Laboratory

Abstract

Bacterial air sampling in an animal care laboratory showed that dense aerosols are generated during cage changing and cage cleaning. Reyniers and Andersen sampling showed that the airborne bacteria numbered 50 to 200 colony-forming units (CFU)/ft3 of air. Of the viable particles collected by Andersen samplers, 78.5% were larger than 5.5 ,m. A low velocity laminar air flow system composed of high-efficiency particulate air (HEPA) filters and a ceiling distribution system maintained the number of airborne viable particles at low levels, generally less than 2 CFU/ft3. Vertical air flow of 15 ft/min significantly reduced the rate of airborne infection by a strain of Proteus mirabilis. Other factors shown to influence airborne infection included type of cage utilized, the use of bedding, the distance between cages, and the number of animals per cage. Accidental airborne infection in an animal care facility can influence the validity of experimental results and the economics of laboratory animal care (6). It is not an uncommon practice to maintain laboratory animals under observation for their normal life span, especially in toxicity

Mass Airflow Cabinet for Control of Airborne Infection of Laboratory Rodents

“…The vertical air velocity used in this hood (19 cm/s) is substantially lower than that conventionally employed in laminar air flow systems (50 cm/s), but we have shown that lowered air velocities are effective in elimination of airborne contamination in tissue culture laboratories and operating rooms and elimination of airborne infection in animal laboratories in controlled studies (5,7,11,12).…”

“…This restriction of infectious foci inside the cabinet may be due to the unidirectional air flow and the absence of bedding. We have previously demonstrated how these two factors can inluence spread of airborne infection (11).…”

“…In animal laboratory applications, we have previously demonstrated that a mass airflow (MAF) system significantly reduced or eliminated airborne spread of bacterial infections depending on conditions of the experiment (11,12). van der Waaij adapted horizontal and vertical laminar airflow cabinets for housing axenic mice without the use of germ-free isolators, and maintained them germ free when the cages were 10 cm from cages of conventional mice (16).…”