Culture and real-time quantitative PCR to detect environmental nontuberculous mycobacteria in a clinical care center

Nontuberculous mycobacteria (NTM) are opportunistic pathogens widely distributed in natural and human-built environments. Despite their environmental frequency, the airborne presence and distribution of NTM in clinical settings remain poorly understood. In this study, we assessed NTM in air and floor surface samples within a clinical care center using both culture-based and qPCR methods. Air and floor samples were collected across three days from patient rooms, a dictation room, and a hallway using a wetted wall cyclone (WWC), a gelatin filter-based air sampler, and foam swabs. Using the culture-based method, viable NTM were recovered from three floor surface swabs, while all other samples were culture-negative. qPCR analysis revealed frequent NTM detection in air samples, with a higher positivity rate from WWC samples compared to gelatin filters, despite total bacterial count (TBC) being two orders of magnitude higher in gelatin filter samples. The highest frequency of qPCR-tested NTM-positive samples was observed in the clinic hallway, suggesting that airflow dynamics and patient movement influence bacterial redistribution. Floor swabs showed transient NTM detection patterns, likely influenced by environmental deposition and routine cleaning. Despite confirmed Mycobacterium avium complex (MAC) infections among patients, M. avium was not detected in any environmental samples, suggesting species-specific aerosolization differences. Although viable NTM were not recovered from air samples, the high qPCR positivity suggests the potential presence of airborne NTM that may not have been captured by culture due to viability loss or sampling limitations. These findings emphasize the role of air sampling methodologies in capturing NTM and highlight the need to better understand the factors influencing the persistence and distribution of airborne NTM in clinical environments.