PM2.5-associated bacteria in ambient air: Is PM(2.5)exposure associated with the acquisition of community-acquired staphylococcal infections?

Abstract

Particulate matter (PM), a major component of air pollution, is an important carrier medium of various chemical and microbial compounds. Air pollution due to PM could increase the level of bacteria and associated adverse health effects. Staphylococci as important opportunistic pathogens that cause hospital- and community-acquired infections may transmit through air. This study aimed to obtain knowledge about the concentration of airborne bacteria as well as staphylococci associated with particulate matter with a diameter of less than 2.5 micrometers (PM2.5) in ambient air. The impact of meteorological factors including ultraviolet (UV) index, wind speed, temperature, and moisture on microbial concentrations was also investigated. Quartz filters were used to collect PM(2.5)and associated bacteria in ambient air of a semiarid area. Airborne bacteria were quantified by culture method andStaphylococcusspecies identified by molecular methods. The mean (SD) concentration of PM(2.5)and airborne bacteria was 64.83 (24.87) mu g/m(3)and 38 (36) colony forming unit (CFU)/m(3), respectively. The results showed no significant correlation between the levels of PM(2.5)and concentrations of bacteria (p < 0.05). Staphylococcus species were detected in 8 of 37 (22) samples in a concentration from 3 to 213 CFU/m(3).S. epidermidiswas detected with the highest frequency followed byS. gallinarumandS. hominis, butS. aureusand methicillin-resistantStaphylococcus aureus(MRSA) were not detected. No significant correlation between the concentrations of bacteria with meteorological parameters was observed (p < 0.05). Our finding showed that, although the study area is sometimes subject to air pollution from PM2.5, the concentration of PM2.5- associated bacteria is relatively low. According to the results, PM(2.5)may not be a source of community-associated staphylococcal infections.