Characterisation of indoor viable microorganisms in residential homes

摘要

Background: Inhalation of airborne microorganisms in indoor environments has been associated with the development of respiratory disorders. Aim: Assessment of culturable microorganisms (bacteria and fungi) in different residential indoor environments and to examine the role of temperature, humidity, and indoor air quality. Methods: The study was performed using single-stage viable cascade impactor (Biostage) and VersaTrap spore trap cassette with the help of QuickTake 30 sample pump. The sampling device was equipped with an electronic data logger (HOBO) to record temperature and relative humidity during the sample collection. Air was passed through different selective media for growth of bacteria and fungi. Numbers of colonies were counted and identified to the genus level was done by staining and biochemical tests. Sampling characteristics included housing condition, room occupancy, cooking procedure, and seasonal variation. Results: The average concentration of bacteria and fungi in indoor air was 840±320 CFU/m3 and 105±28 CFU/m3 respectively. The predominant bacterial species identified by culture techniques were Coliforms, Pseudomonas, Staphylococcus, Streptococcus, and Clostridium. Actinomycetes and Aspergillus were dominant fungal species in indoor air samples. We found a significant correlation between indoor microbial content in kitchens using biomass fuel compared to other rooms. Bacteria levels also exhibited a seasonal variation, usually higher in the summer. Ongoing studies are comparing incidence and types of health outcomes in the inhabitants in multiple sets of households with varying degree of humidity (some with molds on walls), that use biomass fuel vs. liquid petroleum gas, taking into consideration seasonal variations. Conclusions: Our study indicates that apart from typical health impacts due to various particles in indoor air, these environments can promote the survival and growth of microorganisms. When in synergy, these factors may have negative influence on respiratory health outcomes of the inhabitants.