Microorganisms in the Indoor Environment Analysis and Structure-Bioactivity Relationships

University dissertation from Divison of Medical Microbiology

Abstract: Inhalation of air-borne microorganisms and components thereof can cause illnesses and diseases. However, lack of specific and sensitive methods for exposure assessment can pose problems in predicting health outcomes. Characterization of microbial load from indoor environments using gas chromatography-mass spectrometry (GC-MS) and/or tandem mass spectrometry (GC-MSMS) as well as various bioassays (Limulus assay and in-vitro cell stimulation analysis using the A549 cell line) was the focus of this thesis. GC-MS and GC-MSMS make use of the fact that microorganisms contain unique chemical structures that can be used as markers. Three chemical markers, namely, 3-hydroxy fatty acids (3-OH FAs; marker of LPS), muramic acid (MuAc; marker of peptidoglycan) and ergosterol (marker of fungi) were analyzed. The specificity of GC-MSMS was superior to GC-MS with regard to co-eluting compounds. The selective hydrolysis and extraction methods enabled simultaneous analysis of different markers from a single sample aliquot. The amounts of LPS present in house dust (calculated using 3-OH FAs with chain lengths of 10-14 carbon atoms) and bioactivity (as measured by Limulus analysis) gave correlation coefficients (r) of 0.60 and 0.88. In a study involving exposure of human subjects to airborne material in a swine confinement building, serum IL-6 correlated with 3-OH FAs and MuAc (r=0.50 and r=0.46 respectively). MuAc also related with change in body temperature (r=0.57). In-vitro analysis using the cell line A549 showed house dust to be a potent stimulant of IL-8 and IL-6 production by this cell line.

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