Page:NIOSH Manual of Analytical Methods - 0900.pdf/1

 Rh METHOD: 0900, Issue 1

BIOLOGICAL INDICATOR OF: exposure to M. tuberculosis

SYNONYMS: TB, tubercle bacilli

SAMPLING

FILTER (PFTE filter, 37-mm) 4 L/min or higher [1] if the airborne particle concentration is low, sample for at least 8 hours and/or use high volume sampling; in the laboratory studies, sampling times were 10 min none follow CDC guidelines for interstate shipment of human pathogen (42 CFR Part 72); may ship at ambient temperature 1 week or more at ambient temperature; indefinitely at –20 °C 2 or more field blanks

MEASUREMENT

POLYMERASE CHAIN REACTION (PCR)/MICROPLATE READER [2] M. tuberculosis 450 nm 3 laboratory negative PCR controls, all should read less than 0.25 absorbance units; 2 laboratory positive controls, both should read 2.0 absorbance units or greater purified M. tuberculosis H37Ra DNA, 1–300 copies; H37Ra mycobacteria, approximately 4 to 1950 particles (all higher ranges will test positive) approximately 20 mycobacteria particles (from air samples)

APPLICABILITY: This is a qualitative method which permits the detection of airborne M. tuberculosis particles. It will detect approximately 20 or greater M. tuberculosis particles. This method does not indicate how many particles were detected.

INTERFERENCES: Positive interferences, M. bovis, M. bovis BCG; negative interferences, metals, and other unknown airborne particulate matter. (Note: to detect suspected negative interferences, spike field samples which resulted in negative readings with M. tuberculosis H37Ra DNA or H37Ra particles and rerun assay. Alternately, the Roche positive control may be used instead of H37Ra.)

OTHER METHODS: The measurement technique was originally developed by Roche Diagnostic Systems for the analysis of clinical samples [2]. Various other M. tuberculosis detection methods are now available, such as Gen-Probe [3,4] and Digene [5]. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition