Use of PCR for the detection of airborne tuberculosis (TB): a novel sampling and analytical method.
Schafer-MP; Fernback-J; Martinez-K
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas. Fairfax, VA: American Industrial Hygiene Association, 1997 May; :12
No rapid, sensitive method exists to detect airborne TB expelled from the human respiratory tract in indoor air. Previous attempts to detect airborne TB using Andersen N6 single stage samplers containing Middlebrook 7H11 agar plates, for example, resulted in fungal overgrowth, and the detection of bacteria not related to acid fast mycobacteria. No slow-growing mycobacteria, such as TB, were detected. Currently, medical and epidemiologic surveillance of populations is conducted in order to detect TB skin-test conversions as an indicator of aerial dissemination in an institution. A rapid, specific, in vitro DNA amplification technique, the polymerase chain reaction (PCR) was evaluated using an avirulent mycobacteria strain, H37Ra, as a model for pathogenic TB. The assay detected as little as 3fg (< 1 copy) of purified H37Ra DNA and less than 5 H37Ra mycobacteria. In order to evaluate collection efficiency, liquid cultures of H37Ra were prepared for aerosolization in a bioaerosol chamber. The size distribution of the H37Ra mycobacteria present in the liquid cultures was determined using the NIH Image system (version 1.57). The initial number of mycobacteria per mL was obtained by counting an aliquot of the culture in a Petroff-Hausser counting chamber. The Andersen 6-Stage, 28.3 L/min, was employed as a reference sampler. Two plastic disposable filter cassettes with 1.0 micron teflon filters were operated at 5 L/min as test samplers, and the filters subjected to the PCR assay. The mycobacteria agar plates from the Andersen 6-Stage were placed in a 75% CO2 incubator at 37 degrees C for 6-8 weeks. Results to date indicate that the PCR is comparable to the Andersen 6-Stage in sensitivity. However, the PCR results can be obtained in 1 day. No culturing or sample purification is required. Preliminary field testing of the PCR method was conducted in a hospital.
Airborne-particles; Humans; Men; Women; Respiration; Bacteria; Epidemiology; Skin-tests; Sampling; Sampling-methods; Analytical-methods
American Industrial Hygiene Conference and Exposition, May 19-23, 1997, Dallas, Texas