Airborne concentrations of bacteria in a hospital environment in Singapore

A study was undertaken to determine typical concentrations of airborne bacteria in a local hospital in the tropical environment of Singapore. Aerial sampling was conducted at various locations within the air-conditioned hospital building including the main lobby, a visitor restricted ward and a pharmacy. Concentrations of airborne bacteria exceeded available local guidelines for indoor air quality (i.e., 500 colony forming units m(-3) air in an air-conditioned environment) in the lobby and pharmacy, but not in the visitor restricted ward. Results showed that the occupant density was the key factor influencing the level of airborne bacteria, but humidity was also important depending on the particular location within the hospital. Bacteria identified were representative of normal microflora of the skin, respiratory and gastro-intestinal tracts, but also included the opportunistic pathogens Acinetobacter and Flavobacterium spp.