The abundance of urban endotoxins as measured with an impinger-based sampling strategy
Endotoxins are components of Gram-negative bacteria with inherently high pro-inflammatory potential. In an urban environment, airborne endotoxins may associate with pollutants such as particulate matter, increasing the severity of the immune response by acting as a natural adjuvant to augment inflammatory respiratory disease development. Here, we present a closer look at outdoor urban endotoxins by applying a microbial-targeted collection strategy. Results from 87 samples distributed throughout the city of Antwerp ranged from 0.45 to 93.71 EU/m3, with a geometric mean of 4.49 EU/m3 and 95% confidence interval of 3.53–5.71 EU/m3. Sample collection was also coupled with the use of a Coulter counter, for which the particle count (2.5–10 μm/m3) showed a significant correlation with endotoxin concentration (R2 = 0.24; p < 0.0001; n = 64). In addition, the analysis of the cultivable bacterial colony-forming units on Reasoner’s 2A agar (expressed CFU/m3) showed to be a good indicator for airborne endotoxins (R2 = 0.57; p < 0.0001; n = 58). Moreover, identification of dominant bacterial colonies on these culture plates gave some indications on potential sources of these urban outdoor bacteria and endotoxins.
KeywordsEndotoxin Urban air quality Particulate matter Lipopolysaccharides Respiratory health
We acknowledge the valuable help of Karin Van den Bergh (SPHERE, University Antwerp, Belgium) for her assistance with the Coulter counter measurements. This research was financially supported by the University of Antwerp (BOF), EUROSA, and the Fund for Scientific Research in Flanders (KaN research Grant Number 1507114N). Serena Moretti is currently holding a Ph.D. scholarship (FWO aspirant).
- Lane, D. J. (1991). 16S/23S rRNA sequencing (Nucleic acid techniques in bacterial systematics). New York: Wiley.Google Scholar
- Morgenstern, V., Carty, C. L., Gehring, U., Cyrys, J., Bischof, W., & Heinrich, J. (2005). Lack of spatial variation of endotoxin in ambient particulate matter across a German metropolitan area. Atmospheric Environment, 39(36), 6931–6941. https://doi.org/10.1016/j.atmosenv.2005.08.022.CrossRefGoogle Scholar
- Ryan, P. H., Bernstein, D. I., Lockey, J., Reponen, T., Levin, L., Grinshpun, S., et al. (2009). Exposure to traffic-related particles and endotoxin during infancy is associated with wheezing at age 3 years. American Journal of Respiratory and Critical Care Medicine, 180(11), 1068–1075. https://doi.org/10.1164/rccm.200808-1307OC.CrossRefGoogle Scholar
- Schins, R. P. F., Lightbody, J. H., Borm, P. J. A., Shi, T., Donaldson, K., & Stone, V. (2004). Inflammatory effects of coarse and fine particulate matter in relation to chemical and biological constituents. Toxicology and Applied Pharmacology, 195(1), 1–11. https://doi.org/10.1016/j.taap.2003.10.002.CrossRefGoogle Scholar
- Spaan, S., Heederik, D. J., Thorne, P. S., & Wouters, I. M. (2007). Optimization of airborne endotoxin exposure assessment: Effects of filter type, transport conditions, extraction solutions, and storage of samples and extracts. Applied and Environmental Microbiology, 73(19), 6134–6143.CrossRefGoogle Scholar
- Thorne, P. S., Bartlett, K. H., Phipps, J., & Kulhankova, K. (2003). Evaluation of five extraction protocols for quantification of endotoxin in metalworking fluid aerosol. Annals of Occupational Hygiene, 47(1), 31–36.Google Scholar
- Thorne, P. S., Perry, S. S., Saito, R., O’Shaughnessy, P. T., Mehaffy, J., Metwali, N., et al. (2010). Evaluation of the Limulus amebocyte lysate and recombinant factor C assays for assessment of airborne endotoxin. Applied and Environmental Microbiology, 76(15), 4988–4995. https://doi.org/10.1128/AEM.00527-10.CrossRefGoogle Scholar
- VMM. (2011). Comparative PM10 and PM2.5 measurements in Flanders, 2010 campaign (Depot number: D/2011/6871/022). Flemish Environmental Agency, Section Air. Philippe D’Hondt (Ed.). Available at https://www.scribd.com/document/139526198/Comparative-PM-2010-TW. Accessed 3 July 2018.