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Detection and characterization of airborne Mycobacterium tuberculosis H37Ra particles, a surrogate for airborne pathogenic M. tuberculosis.

Schafer MP; Fernback JE; Ernst MK
Aerosol Sci Tech 1999 Feb; 30(2):161-173
There is currently no direct sampling and analytical method available for monitoring airborne environmental Mycobacterium tuberculosis (M. tuberculosis ) expelled from the human respiratory tract. Traditional sampling and analytical methods fail to detect airborne environmental M. tuberculosis . To circumvent the need for traditional microbial culturing in order to detect and identify environmental M. tuberculosis , a commercial DNA diagnostic method involving the polymerase chain reaction (PCR) coupled with an enzymatically-generated color reaction was interfaced with air sampling methods. Using a laboratory-conditioned avirulent mycobacteria strain, M. tuberculosis H37Ra, as a surrogate for pathogenic M. tuberculosis , a single copy of purified M. tuberculosis H37Ra DNA could be detected. A small number of lysed mycobacteria particles, < 10 particles, could also be detected. To develop a sampling method for airborne M. tuberculosis , liquid suspensions of M. tuberculosis H37Ra were aerosolized in a bioaerosol chamber 3.7 m long with a square cross-sectional area of 0.61 m. Samples were collected for PCR analyses using polytetrafluoroethylene filters. Two types of samplers were employed, a plastic, disposable filter cassette and an eightstage cascade impactor called a micro-orifice uniform deposit impactor (MOUDITM ). An Andersen six-stage (viable) particle sizing sampler was employed as a reference sampler since laboratory-conditioned aerosolized M. tuberculosis strains can be cultured. Although the M. tuberculosis H37Ra rod-shaped particles had a mean length of 6.6 mu m, the airborne particles were predominantly collected on the Andersen 4-6 stages representing an aerodynamic diameter 50% cut point range of 0.6-2.1 mu m and on the MOUDITM 4-7 stages representing an aerodynamic diameter 50% cut point range of 0.3 to 1.8 mu m. The PCR analyses could be completed in 1-1.5 days, in contrast to the traditional culturing methods which required a minimum of 3-5 weeks. This approach could be used to study the expulsion of infectious particles from patients and may permit risk-assessment studies in regard to personal respiratory protection and the evaluation of environmental controls.
Sampling-methods; Sampling-equipment; Sampling; Analytical-methods; Analytical-processes; Airborne-fibers; Airborne-particles; Air-sampling; Air-sampling-equipment; Aerosols; Aerosol-sampling; Aerosol-particles; Pathogens; Respiratory-infections; Respiratory-system-disorders; Pulmonary-disorders; Pulmonary-system-disorders; Bacterial-cultures; Bacterial-disease; Bacterial-dusts; Statistical-analysis
Millie P. Schafer, U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, MS R-7, Cincinnati, OH 45226-1099
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Aerosol Science and Technology
Page last reviewed: August 1, 2022
Content source: National Institute for Occupational Safety and Health Education and Information Division