Distribution and characteristics of airborne bacteria in long-term care facilities in Taipei, Taiwan

Objectives: This study investigated the characteristics and determinants of airborne bacteria in long-term care facilities in Taiwan. Methods: We did intensive environmental samplings, including airborne culturable bacteria and major indoor air quality factors, in five long-term care facilities in Taipei. We used statistical models to evaluate the environmental determinants of the levels of indoor bacterial colonies. Results: The average total bacterial colony concentrations in the study facilities ranged from 282 to 812 CFU/m ³. The mean bacterial colony concentrations in several facilities exceeded 500 CFU/m³, the maximum level recommended by the Taiwan Environmental Protection Administration. Bacilli and cocci were the dominant bacteria in the study facilities. The concentrations of Gram-negative bacterial colonies were higher than those of Gram-positive bacteria. In some study facilities, the bacterial colony levels near the diffusers of AC (air conditioner) or HVAC (heating, ventilating and air conditioning) systems were higher than indoor concentrations in general, indicating that AC and HVAC systems might be potential sources of microorganisms. According to the results of multiple regression models, sampling time, different facilities, using an air cleaner or not, carbon dioxide levels, and number of people were significantly associated with indoor bacterial concentrations. Conclusions: Building characteristics, ventilation rate, number of people, and cleaning method and frequency were essential factors influencing indoor microbial distributions in long-term care facilities. Effective environmental control can reduce disease transmission and protect the health and safety of residents and staff in long-term care facilities.