Viable airborne microbial counts from air-cooling units with and without complaints of urine and body odors
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Viable airborne microbial counts are commonly used in indoor air quality (IAQ) assessment, but studies linking the microbial counts to a specific type of indoor microbial contamination are limited. We hypothesize that the airborne microbial counts can differentiate air-cooling units with and without complaints of urine and body odors. The keratinolytic property of some isolated bacteria prompts to the hypothesis that keratinase is present in the units to break down keratins, structural proteins that form human skin scales, as sources of amino acids and ammonium to produce the odors. Seven bacterial species and four fungal species were identified in the units and room air. Airborne Staphylococcus haemolyticus and Methylobacterium organophilum counts contributed the most to the microbial dissimilarities of units with and without odor complaints. Keratinolytic bacteria and a methylotrophic bacterium were abundant in the units. All the units contained ammonium, and keratinase activity was higher in the units with odor complaints. Extracellular keratinase activity was more effective at 20 °C than at 30 or 4 °C. Keratinolytic bacteria produced high levels of ammonium in the culture with skin cells. Viable airborne microbial counts can help IAQ inspectors to identify potential odor-causing air-cooling units. Keratins may be broken down in the units and associated with the odor complaints.
KeywordsIndoor air quality Microbial odor emission Air-conditioning systems Bioaerosols
We thank the HKBU Estate Office and Health and Safety team for assisting the field investigation and the Environment and Conservation Fund (Grant Ref.: ECF89/2015) for supporting this study.
- Anesti, V., Vohra, J., Goonetilleka, S., McDonald, I. R., Straubler, B., Stackebrandt, E., et al. (2004). Molecular detection and isolation of facultatively methylotrophic bacteria, including Methylobacterium podarium sp. nov., from the human foot microflora. Environmental Microbiology, 6(8), 820–830.CrossRefGoogle Scholar
- Bressollier, P., Letourneau, F., Urdaci, M., & Verneuil, B. (1999). Purification and characterization of a keratinolytic serine proteinase from Streptomyces albidoflavus. Applied Environmental Microbiology, 65(6), 2570–2576.Google Scholar
- Clarke, K. R., & Warwick, R. M. (2001). Change in marine communities: An approach to statistical analysis and interpretation. Plymouth: Primer-E.Google Scholar
- Hong Kong Environmental Protection Department. (2003). Indoor Air Quality Management Group. A guide on indoor air quality certification scheme for offices and public places. The Government of the Hong Kong Special Administrative Region.Google Scholar
- Hugenholtz, P., & Fuerst, J. A. (1992). Heterotrophic bacteria in an air-handling system. Applied Environmental Microbiology, 58(12), 3914–3920.Google Scholar
- U.S. EPA. (2013). IRIS toxicological review of ammonia (Revised external review draft). U.S. Environmental Protection Agency, Washington, DC, EPA/635/R-13/139a.Google Scholar
- Uy, M. M., Uy, J., Carvajal, T. M., Castro, C. Z. R., Ho, H. T., & Lee, A. C. (2013). Pink pigmented facultative methylotrophic (PPFM) bacteria isolated from the hair scalp and nasal cavity. Phillippine Journal of Systematic Biology, 7, 13–21.Google Scholar
- Yano, T., Kubota, H., Hanai, J., Hitomi, J., & Tokuda, H. (2013). Stress tolerance of Methylobacterium biofilms in bathrooms. Microbes and Environment, 28(1), 87–95.Google Scholar