Do non-conventional types of respiratory control (Queen Charlotte, buff, bandana) reduce the infectiousness of patients with tuberculosis?

Abstract

Tuberculosis (TB) is an airborne disease spread through person-to-person transmission. To reduce TB burden, transmission needs to be interrupted. This is especially true for extensively-and multi-drug resistant TB. The City of Cape Town aims to reduce TB transmission (and other airborne diseases) by promoting the use of alternative forms of respiratory protection (RP) that are more acceptable by communities outside health facilities, however, need data on if these RPs reduce infectiousness. This study was initiated pre-COVID-19. We aimed to test the degree to which different RP reduce respirable infectious Mycobacterium tuberculosis (Mtb) particles in aerosols made naturally by TB patients. We did this using a Human Aerosol Chamber that simultaneously captures infectious aerosols on solid media using a Anderson Cascade Impactor and in liquid media using SKC Biosamplers. These can be cultured (MGIT 960 culture) or quantified using molecular tests like Xpert MTB/RIF Ultra. Digital data such as particle counts, humidity and CO2 were also captured. We did this for both tidal breathing and coughing for TB-positive pre-treatment patients (n=28) who were allocated to wear a form of RP (surgical mask=8, queen charlotte=8, cyclist buff=8, bandana=4) and compared the values obtained on an adjacent day when no RP was worn. We found that 6/28 and 5/28 (p=0.736) patients were positive (by either ACI, MGIT and/or Ultra) for tidal breathing, 12/28 and 7/28 (p=0.158) for spontaneous cough and 15/28 and 7/28 (p=0.028) for forced cough with NRP and RP respectively. Particle counts (median interquartile range) for tidal breathing with NRP and RP were 115 (27.2-21500) vs IQR: 8260 (19.3-32600; p=0.610) respectively for tidal breathing, 65.2 (15.3-11600) vs. 27.3 (13-11300; p=0.461) for spontaneous cough and 65.2 (17.9-28075) vs 20.3 (13-18775; p = 0. 001) for forced cough, respectively. Our results show that that non-conventional RPs might be effective at reducing culturable respiratory particles in TB patients, however, larger sample sizes are needed to accurately determine effectiveness, especially across different respiratory manoeuvres.