Polymerase chain reaction used for the detection of airborne Mycobacterium tuberculosis in health care settings

Background: Tuberculosis (TB) has re-emerged as a major infectious disease in several areas in the world. Airborne tubercle bacilli produced by individuals with pulmonary TB and droplet nuclei remain suspended in the air for a long time. This study attempts to use a sensitive polymerase chain reaction (PCR) analytic method coupled with a filter sampling method to detect the presence of airborne Mycobacterium tuberculosis (MTb) in health care settings. Methods: Patients with TB history were recruited from a medical intensive care department and negative-pressure isolation rooms at Chang Gung Memorial Hospital in Taichung City, Taiwan, Republic of China. The exhaled gas from different patients with TB who were mechanically ventilated in the intensive care department was collected using a polycarbonate (PC) membrane or polytetrafluoroethylene (PTFE) filter. Airborne MTb concentrations in air exhausted through a bacterial filter attached to a mechanic ventilator were studied. Indoor air samples were taken through a 3-piece cassette with a filter (PC/PTFE) in patient rooms. MTb concentrations in these filters were analyzed using the PCR method. Results: Overall, 75% (12/16) of the exhaled-gas samples in PTFE filters and 25% (4/16) of samples in PC filters were detected as having positive MTb-specific DNA products. Exhausted air from the bacterial filters in mechanic ventilators was found to have positive PCR results (57% in PC filters and 14% in PTFE filters) for MTb. Both negative-pressure isolation rooms and outpatient department areas in the TB center had positive samples (40%-60% in PC/PTFE filters) containing MTb by PCR amplification. Conclusions: Health care settings were sufficient for various risk factors, including physical, chemical, and biologic hazards. Infectious agents are produced by aerosolization that results in human respiratory-related diseases. The indoor air quality of the entire hospital environment should, therefore, be monitored by health care personnel and the public.