Face Mask Sampling for the Detection of Mycobacterium tuberculosis in Expelled Aerosols

Abstract

BackgroundAlthough tuberculosis is transmitted by the airborne route, direct information on the natural output of bacilli into air by source cases is very limited. We sought to address this through sampling of expelled aerosols in face masks that were subsequently analyzed for mycobacterial contamination.MethodsIn series 1, 17 smear microscopy positive patients wore standard surgical face masks once or twice for periods between 10 minutes and 5 hours; mycobacterial contamination was detected using a bacteriophage assay. In series 2, 19 patients with suspected tuberculosis were studied in Leicester UK and 10 patients with at least one positive smear were studied in The Gambia. These subjects wore one FFP30 mask modified to contain a gelatin filter for one hour; this was subsequently analyzed by the Xpert MTB/RIF system.ResultsIn series 1, the bacteriophage assay detected live mycobacteria in 11/17 patients with wearing times between 10 and 120 minutes. Variation was seen in mask positivity and the level of contamination detected in multiple samples from the same patient. Two patients had non-tuberculous mycobacterial infections. In series 2, 13/20 patients with pulmonary tuberculosis produced positive masks and 0/9 patients with extrapulmonary or non-tuberculous diagnoses were mask positive. Overall, 65% of patients with confirmed pulmonary mycobacterial infection gave positive masks and this included 3/6 patients who received diagnostic bronchoalveolar lavages.ConclusionMask sampling provides a simple means of assessing mycobacterial output in non-sputum expectorant. The approach shows potential for application to the study of airborne transmission and to diagnosis.

Twenty-four hour face mask sampling in pulmonary tuberculosis reveals three distinct patterns of bacterial aerosol production dissociated from conventional markers of transmission risk

“…We cannot say what proportion of the signals detected here represent potentially infective bacteria as our PCR would have detected DNA from both alive and dead bacteria. We note that signals from viable bacteria comparable to those detected here, were reported in our previous study 4 . Moreover, the culturable signals noted above in association with cough 2,3,19 would not have detected in the bacterial that are incapable of forming colonies on solid media and require liquid culture and supplementation for their growth 25 .…”

“…As in our previous work 4 , we have assigned bacillary output recovered from this mask sample to be in aerosols, although we acknowledge that a range of particles including those outside the respirable range are likely included. We have used the terms mask and aerosol sampling interchangeably to denote results from this sample.…”

“…We have previously reported on a novel Mask Aerosol Sampling System (MASS) that captures Mtb directly from patients under natural conditions 4 , offering the possibility for studying this important question.…”

Capture and visualization of liveMycobacterium tuberculosisbacilli from tuberculosis bioaerosols

“…While molecular methods have enabled consistent and reliable detection of Mtb DNA in bioaerosols (30)(31)(32), these approaches cannot distinguish live from dead organisms nor do they allow investigations of the physiological state(s) of the aerosolized bacilli. The method of bacillary capture is also key: approaches based on forced or induced cough might not reflect natural transmission events (33,34), whereas face-mask and related aerosol sampling methodologies either make live-cell analyses impossible (35) or require downstream in vitro propagation (via microbiological culture) (36), unavoidably altering the physiological and metabolic state of the captured samples.…”

Mitteilungsseiten des Deutschen Zentralkomitees zur Bekämpfung der Tuberkulose (DZK)

“…Die Entwicklung eines wirksamen Impfstoffes ist einer der Kernpunkte in der von der WHO entwickelten End-TB-Strategie. [5,6]. Für die Resistenztestung gilt die kulturelle Untersuchung als Goldstandard.…”