title: Face mask sampling for the detection of Mycobacterium tuberculosis in expelled aerosols.
abstract: BACKGROUND
  Although 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.
  
  
  METHODS
  In 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.
  
  
  RESULTS
  In 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.
  
  
  CONCLUSIONS
  Mask 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.
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
authors.forename: Caroline M L
authors.initials: CM
authors.lastname: Williams
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
authors.forename: Eddy S G
authors.initials: ES
authors.lastname: Cheah
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom; Department of Clinical Microbiology, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom.
authors.forename: Joanne
authors.initials: J
authors.lastname: Malkin
authors.affiliation: Department of Clinical Microbiology, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom.
authors.forename: Hemu
authors.initials: H
authors.lastname: Patel
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Jacob
authors.initials: J
authors.lastname: Otu
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Kodjovi
authors.initials: K
authors.lastname: Mlaga
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Jayne S
authors.initials: JS
authors.lastname: Sutherland
authors.affiliation: Medical Research Council Unit, Banjul, The Gambia.
authors.forename: Martin
authors.initials: M
authors.lastname: Antonio
authors.affiliation: Department of Clinical Microbiology, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom.
authors.forename: Nelun
authors.initials: N
authors.lastname: Perera
authors.affiliation: Department of Respiratory Medicine, Glenfield Hospital, Leicester, United Kingdom.
authors.forename: Gerrit
authors.initials: G
authors.lastname: Woltmann
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom; Department of Respiratory Medicine, Glenfield Hospital, Leicester, United Kingdom; National Institute of Health Research Respiratory Biomedical Research Unit, Glenfield Hospital, Leicester, United Kingdom.
authors.forename: Pranabashis
authors.initials: P
authors.lastname: Haldar
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom.
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Garton
authors.affiliation: Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom; Department of Clinical Microbiology, University Hospitals of Leicester NHS Trust, Leicester, United Kingdom.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Barer
mesh_terms: D000336:Aerosols; D000391:Air Microbiology; D005714:Gambia; D006801:Humans; D008397:Masks / Q000382:microbiology*; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D006113:United Kingdom
chemical_list: D000336:Aerosols