Introduction
In modern societies, people spend most of their time indoors. For Americans, the proportion is up to about 87%. In indoor air, there are a variety of particles that contain living organisms including different kinds of bacteria, viruses and fungi. These particles are named as bioaerosols that could have direct or potential health effects on individuals associated with infectious diseases, respiratory disease and cancer. Apart from indoor air, different indoor surfaces with which residents contact continually harbour lots of microorganism communities as well. Microbial communities live in our homes and are closely related to us. However, little is known about the diversity and composition of these microbial communities. Studies on microbiological communities on surfaces of hospitals, public restroom and kitchens have been carried out. These researches are definitely meaningful to understand microbial composition and assist to improve indoor environment and prevent the spread of human disease.
The structure of microbial communities can be influenced by a multitude of factors. For example, the materials used in building can affect indoor fungal levels highly. Likewise, indoor environment parameters, such as temperature, humidity and ventilation that human can regulate through the use of air conditioning, appear to affect the microbial composition. In addition, frequent cleaning of home can decrease the diversity of microbial community4 and the presence of domestic animals may increase the abundance of microbes. Thus, the microbial communities can be very different according to different environmental conditions and lifestyles. Compared to western societies with low population densities, Hong Kong is one of the most densely populated metropolises. Because of the discrepant living conditions and lifestyles, it would be significant to study the abundance and diversity of indoor microbial communities in Hong Kong with crowded residential units. Such knowledge will be helpful to create a safe living environment and ensure residents’ health.
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