Aleksandra Sebastian

Characterization of the microbial community in indoor environments: a chemical-analytical approach.

ABSTRACT An integrated procedure is presented whereby gas chromatography-ion trap mass spectrometry is used to determine chemical markers of gram-negative bacterial lipopolysaccharide (3-hydroxy fatty acids with 10 to 18 carbon atoms), gram-positive bacteria (branched-chain fatty acids with 15 and 17 carbon atoms), bacterial peptidoglycan (muramic acid), and fungal biomass (ergosterol) in samples of settled house dust. A hydrolysate of 13C-labeled cyanobacterial cells is used as an internal standard for the first three markers. These analyses require two dust samples, one for 3-OH fatty acids, branched-chain fatty acids, and muramic acid and another for ergosterol. The method may be used to characterize microbial communities in environmental samples.

Asthmatic symptoms among pupils in relation to microbial dust exposure in schools in Taiyuan, China

Microbial exposure has been indicated as significant in the development of asthma and allergy among children. The aim of the study was to test whether microbial exposure and allergens in the school environment are associated with asthmatic symptoms in pupils. Data on asthmatic symptoms and respiratory infections were collected through a questionnaire survey among 1993 pupils aged 11–15 yr in 10 randomly selected schools in Taiyuan, China. Settled dust in classrooms was analysed using tandem gas chromatography‐mass spectrometry for 3‐hydroxy fatty acids, marker of lipopolysaccharide (LPS) from endotoxin, muramic acid (MuA), marker of bacteria and ergosterol (Erg) for fungi, quantifying both culturable and non‐culturable microbes. A total of 29.8% reported daytime attacks of breathlessness, 8.4% wheeze and 1.2% had doctor’s diagnosed asthma. Generally, MuA was negatively associated with wheeze and daytime attacks of breathlessness, the latter of which was negatively associated with Erg to a weaker extent. Total concentration of LPS was positively associated with daytime attacks of breathlessness, but shorter lengths of LPS, C10, C12 and C14 LPS were negatively associated with either wheezing or daytime attacks of breathlessness. For MuA and C10 and C12 of LPS, the associations were independent of airborne allergens and classroom crowdedness, and even independent of the other two microbial markers for MuA. Microbial exposure indicated by certain chemical markers (e.g. MuA) could be protective for asthmatic symptoms, but for LPS (endotoxin), the picture is more complex, varying by different lengths of fatty acids of LPS.

Increased levels of bacterial markers and CO2 in occupied school rooms

Our group previously demonstrated that carbon dioxide (CO2) levels in heavily occupied schools correlate with the levels of airborne bacterial markers. Since CO2 is derived from the room occupants, it was hypothesized that in schools, bacterial markers may be primarily increased in indoor air because of the presence of children; directly from skin microflora or indirectly, by stirring up dust from carpets and other sources. The purpose of this project was to test the hypothesis. Muramic acid (Mur) is found in almost all bacteria whereas 3-hydroxy fatty acids (3-OH FAs) are found only in Gram-negative bacteria. Thus Mur and 3-OH FA serve as markers to assess bacterial levels in indoor air (pmol m(-3)). In our previous school studies, airborne dust was collected only from occupied rooms. However, in the present study, additional dust samples were collected from the same rooms each weekend when unoccupied. Samples were also collected from outside air. The levels of dust, Mur and C10:0, C12:0, C14:0, and C16:0 3-OH FAs were each much higher (range 5-50 fold) in occupied rooms than in unoccupied school rooms. Levels in outdoor air were much lower than that of indoor air from occupied classrooms and higher than the levels in the same rooms when unoccupied. The mean CO2 concentrations were around 420 parts per million (ppm) in unoccupied rooms and outside air; and they ranged from 1017 to 1736 ppm in occupied rooms, regularly exceeding 800-1000 ppm, which are the maximum levels indicative of adequate indoor ventilation. This indicates that the children were responsible for the increased levels of bacterial markers. However, the concentration of Mur in dust was also 6 fold higher in occupied rooms (115.5 versus 18.2 pmole mg(-1)). This further suggests that airborne dust present in occupied and unoccupied rooms is quite distinct. In conclusion in unoccupied rooms, the dust was of environmental origin but the children were the primary source in occupied rooms.

Characterizing microbial exposure with ergosterol, 3-hydroxy fatty acids, and viable microbes in house dust: Determinants and association with childhood asthma

The authors assessed determinants of ergosterol, 3-OH fatty acids (FAs), and viable microbes in vacuum cleaner dust, and investigated the association between these microbial markers and childhood asthma. The authors studied the homes of 36 children who were new cases of childhood asthma and the homes of 36 controls. Home characteristics explained 34% to 44% of the variation in levels of different microbial groups. Determinants of 3-OH FAs were a lower level of cleanliness, having a fireplace, having livestock, and moisture damage; determinants of viable bacteria were the level of home repair needed and the material used in the building frame of the home. Ergosterol was associated with the presence of livestock and the practice of cleaning rugs outside; viable fungi was associated with the material used in the building frame, visible mold, and the practice of cleaning rugs outside. Exposure to mesophilic actinomycetes was nonsignificantly associated with risk of asthma. The authors concluded that the variation of microbial levels in dust could be explained relatively well by home characteristics, and suggested that exposure to mesophilic actinomycetes may increase the risk of new asthma.

A longitudinal study of sick building syndrome among pupils in relation to microbial components in dust in schools in China

There are few longitudinal studies on sick building syndrome (SBS), which include ocular, nasal, throat, and dermal symptoms, headache, and fatigue. We studied the associations between selected microbial components, fungal DNA, furry pet allergens, and incidence and remission of SBS symptoms in schools in Taiyuan, China. The study was based on a two-year prospective analysis in pupils (N=1143) in a random sample of schools in China. Settled dust in the classrooms was collected by vacuum cleaning and analyzed for lipopolysaccharide (LPS), muramic acid (MuA), and ergosterol (Erg). Airborne dust was collected in Petri dishes and analyzed for cat and dog allergens and fungal DNA. The relationship between the concentration of allergens and microbial compounds and new onset of SBS was analyzed by multi-level logistic regression. The prevalence of mucosal and general symptoms was 33% and 28%, respectively, at baseline, and increased during follow-up. At baseline, 27% reported at least one symptom that improved when away from school (school-related symptoms). New onset of mucosal symptoms was negatively associated with concentration of MuA, total LPS, and shorter lengths of 3-hydroxy fatty acids from LPS, C14, C16, and C18. Onset of general symptoms was negatively associated with C18 LPS. Onset of school-related symptoms was negatively associated with C16 LPS, but positively associated with total fungal DNA. In general, bacterial compounds (LPS and MuA) seem to protect against the development of mucosal and general symptoms, but fungal exposure measured as fungal DNA could increase the incidence of school-related symptoms.

Residential culturable fungi, (1-3, 1-6)-β-d-glucan, and ergosterol concentrations in dust are not associated with asthma, rhinitis, or eczema diagnoses in children

Qualitative reporting of home indoor moisture problems predicts respiratory diseases. However, causal agents underlying such qualitative markers remain unknown. In the homes of 198 multiple allergic case children and 202 controls in Sweden, we cultivated culturable fungi by directly plating dust, and quantified (1-3, 1-6)-β-D-glucan and ergosterol in dust samples from the childs bedroom. We examined the relationship between these fungal agents and degree of parent or inspector-reported home indoor dampness, and microbiological laboratorys mold index. We also compared the concentrations of these agents between multiple allergic cases and healthy controls, as well as IgE-sensitization among cases. The concentrations of culturable fungal agents were comparable between houses with parent and inspector-reported mold issues and those without. There were no differences in concentrations of the individual or the total summed culturable fungi, (1-3, 1-6)-β-D-glucan, and ergosterol between the controls and the multiple allergic case children, or individual diagnosis of asthma, rhinitis, or eczema. Culturable fungi, (1-3, 1-6)-β-D-glucan, and ergosterol in dust were not associated with qualitative markers of indoor dampness or mold or indoor humidity. Furthermore, these agents in dust samples were not associated with any health outcomes in the children.

Extremely low electrical current generated by porcine small intestine smooth muscle alters bacterial autolysin production.

The effect of extremely low electrical currents, identical to those generated by the gut smooth muscle, on bacterial autolysin production in vitro was tested in the present study. When stimulated with these electrical currents, the bacteria Pediococcus pentosaceus 16:1 produced groups of peptidoglycan hydrolases that differed from those produced by the unstimulated (control) bacteria. The autolysins synthesized by the P. pentosaceus 16:1 under extremely low electrical currents were effective against peptidoglycans from the cell walls of various lactic acid bacteria strains, whereas the autolysins from the control bacteria acted exclusively against P. pentosaceus 16:1 cell walls. Thus, it can be predicted that in vivo the electrical currents generated by the intestinal smooth muscles, which can be recorded as the myoelectrical migrating complexes, could regulate lactic acid bacteria strain growth in the gut.