Proinflammatory effects of bacterial cell wall of Pantoea agglomerans: A possible explanation of airborne dermatitis to bioaerosols

Background: Bioaerosol-related airborne dermatitis was reported on e.g. in farmers and sewage workers. Bioaerosols consist of Gram-negative bacteria and so-called microvesicles (MV) emerging as a result of disruption of the bacteria. The present study was aimed at assessing the proinflammatory properties of microvesicles in vitro.

Methods: MV were produced through disruption of the bacterial wall of the Gram-negative bacterium Pantoea agglomerans (Erwinia herbicola). Peripheral blood mononuclear cells (PBMC) of five healthy volunteers were cultured for 6 h, 24 h, 3 days, and 5 days with dilution series of MV ranging from 0.48 - 1500 µg/ml. The following variables were observed: secretion of IFN-γ and TNF-α (ELISA and ELISPOT assays), intensity of cell proliferation (LPT), expression of surface markers CD8, CD14, CD16, CD25, CD69, CD80, CD83, HLA-DR, the apoptosis marker Annexin V, and PI permeability (flow cytometry).

Results: After 24 hours, a clear dose-dependent response to MV was seen for IFN-γ production starting already with the lowest MV concentration of 0.48 µg/ml (p=0.042). As for TNF-α, a significant (p=0.05) increase in the production of this cytokine was seen after 3 days at MV concentrations of 300 µg/ml or higher. On the LPT, there was a clear and significant dose-response to MV after 5 days (p=0.001). Regarding expression of cell surface markers, the only phenomenon seen in all donors was the decrease in the number of CD14(+)CD83(+) cells with increasing MV concentration (probably due to increased MoDC maturation).

Conclusion: We have shown that microvesicles are biologically active in PBMC cultures in a dose-dependent manner. IFN-γ production was increased already at lowest MV doses tested. These results explain clinical observations on the proinflammatory effect of bioaerosols on the skin.

Related articles:

1. Spiewak R, Skorska C, Gora A, Horoch A, Dutkiewicz J. Young farmers with cellular reactivity to airborne microbes suffer more frequently from work-related skin symptoms and allergic dermatitis. Ann Agric Environ Med 2001; 8 (2): 255-259.
2. Spiewak R, Gora A, Dutkiewicz J. Work-related skin symptoms and type I allergy among eastern-Polish farmers growing hops and other crops. Ann Agric Environ Med 2001; 8 (1): 51-56.
3. Spiewak R, Skorska C, Dutkiewicz J. Occupational airborne contact dermatitis caused by thyme dust. Contact Dermatitis 2001; 44 (4): 235-239.
4. Spiewak R, Krysinska-Traczyk E, Sitkowska J, Dutkiewicz J. Microflora of allergenic pollens - a preliminary study. Ann Agric Environ Med 1996; 3 (2): 127-130.
5. Spiewak R, Skorska C, Prazmo Z, Dutkiewicz J. Bacterial endotoxin associated with pollen as a potential factor aggravating pollinosis. Ann Agric Environ Med 1996; 3 (1): 57-59.
6. Spiewak R. Occupational dermatoses among Polish private farmers, 1991-1999. Am J Ind Med 2003; 43 (6): 647-655.
7. Spiewak R, Dutkiewicz J. Occupational airborne and hand dermatitis to hop (Humulus lupulus) with non-occupational relapses. Ann Agric Environ Med 2002; 9 (2): 249-252.
8. Spiewak R, Gora A, Horoch A, Dutkiewicz J. Atopy, allergic diseases and work-related symptoms among students of agricultural schools: first results of the Lublin Study. Ann Agric Environ Med 2001; 8 (2): 261-267.

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Institute of Dermatology, Krakow, Poland

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Specjalista dermatolog i wenerolog, Kraków