Bacterial and fungal components in house dust of farm children, Rudolf Steiner school children and reference children--the PARSIFAL Study

Bioaerosol and microbial exposures from residential evaporative coolers and their potential health outcomes: A review

Evaporative cooling is an energy efficient form of air conditioning in dry climates that functions by pulling hot, dry outdoor air across a wet evaporative pad. While evaporative coolers can help save energy, they also have the potential to influence human health. Studies have shown residential evaporative coolers may pull outdoor air pollutants into the home or contribute to elevated levels of indoor bioaerosols that may be harmful to health. There is also evidence that evaporative coolers can enable a diverse microbial environment that may confer early-life immunological protection against the development of allergies and asthma or exacerbate these same hypersensitivities. This review summarizes the current knowledge of bioaerosol and microbiological studies associated with evaporative coolers, focusing on harmful and potentially helpful outcomes from their use. We evaluate the effects of evaporative coolers on indoor bacterial endotoxins, fungal β-(1 → 3)-D-glucans, dust mite antigens, residential microbial communities, and Legionella pneumophila. To our knowledge, this is the first review to summarize and evaluate studies on the influence that evaporative coolers have on the bioaerosol and microbiological profile of homes. This brings to light a gap in the literature on evaporative coolers, which is the lack of data on health effects associated with their use.

The maternal gut microbiome during pregnancy and offspring allergy and asthma

Environmental exposures during pregnancy that alter both the maternal gut microbiome and the infant's risk of allergic disease and asthma include a traditional farm environment and consumption of unpasteurized cow's milk, antibiotic use, dietary fiber and psychosocial stress. Multiple mechanisms acting in concert may underpin these associations and prime the infant to acquire immune competence and homeostasis following exposure to the extrauterine environment. Cellular and metabolic products of the maternal gut microbiome can promote the expression of microbial pattern recognition receptors, as well as thymic and bone marrow hematopoiesis relevant to regulatory immunity. At birth, transmission of maternally derived bacteria likely leverages this in utero programming to accelerate postnatal transition from a Th2 to Th1 and Th17 dominant immune phenotypes and maturation of regulatory immune mechanisms, which in turn reduce the child's risk of allergic disease and asthma. Although our understanding of these phenomena is rapidly evolving, the field is relatively nascent, and we are yet to translate existing knowledge into interventions that substantially reduce disease risk in humans. Here we review evidence that the maternal gut microbiome impacts the offspring's risk of allergic disease and asthma, discuss challenges and future directions for the field, and propose the hypothesis that maternal carriage of Prevotella copri during pregnancy decreases the offspring's risk of allergic disease via production of succinate which in turn promotes bone marrow myelopoiesis of dendritic cell precursors in the fetus.

Microbial diversity in homes and the risk of allergic rhinitis and inhalant atopy in two European birth cohorts

BACKGROUND

Microbial exposures in early childhood direct the development of the immune system and their diversity may influence the risk of allergy development. We aimed to determine whether the indoor microbial diversity at early-life is associated with the development of allergic rhinitis and inhalant atopy.

METHODS

The study population included children within two birth cohorts: Finnish rural-suburban LUKAS (N = 312), and German urban LISA from Munich and Leipzig study centers (N = 248). The indoor microbiota diversity (Chao1 richness and Shannon entropy) was characterized from floor dust samples collected at the child age of 2-3 months by Illumina MiSeq sequencing of bacterial and fungal DNA amplicons. Allergic rhinitis and inhalant atopy were determined at the age of 10 years and analyzed using logistic regression models.

RESULTS

High bacterial richness (aOR 0.19, 95%CI 0.09-0.42 for middle and aOR 0.12, 95%CI 0.05-0.29 for highest vs. lowest tertile) and Shannon entropy were associated with lower risk of allergic rhinitis in LISA, and similar trend was seen in LUKAS. We observed some significant associations between bacterial and fungal diversity measured and the risk of inhalant atopy, but the associations were inconsistent between the two cohorts. High bacterial diversity tended to be associated with increased risk of inhalant atopy in rural areas, but lower risk in more urban areas. Fungal diversity tended to be associated with increased risk of inhalant atopy only in LISA.

CONCLUSIONS

Our study suggests that a higher bacterial diversity may reduce the risk of allergic rhinitis later in childhood. The environment-dependent heterogeneity in the associations with inhalant atopy - visible here as inconsistent results between two differing cohorts - suggests that specific constituents of the diversity may be relevant.

Atopic dermatitis in West Highland white terriers - Part III: early life peripheral blood regulatory T cells are reduced in atopic dermatitis

BACKGROUND

Regulatory T (Treg) cells are involved in homeostasis of immune regulation and suppression of inflammation and T-cell polarisation. Current knowledge regarding the role of Treg cells in the initiation of allergic disease is limited for both people and dogs.

OBJECTIVES

To explore the role of circulating Treg cells and their possible influencing factors, on the development of atopic dermatitis (AD).

METHODS AND MATERIALS

This study followed part of a birth cohort of West Highland white terrier dogs and classified them according to eventual clinical signs of AD (i.e. allergic versus healthy). The Treg phenotypes were assessed longitudinally by flow cytometry at 3, 3-12 and 12-36 months of age, and associated with development of AD. Different early life antigenic factors [endotoxins and allergens in house dust, Toxocara canis-specific immunoglobulin (Ig)E/IgG, allergen-specific and total IgE, skin microbiota] were measured at three months of age, and a possible association with Treg cell levels was assessed.

RESULTS

The percentages of CD4⁺ CD25⁺ Foxp3⁺ Treg cells in healthy dogs were significantly higher at in 3-month-old (mean 4.5% healthy versus 3.3% allergic; P = 0.021) and <1-year-old (4.0% healthy versus 2.9% allergic; P = 0.028) dogs when compared to percentages of Treg cells in dogs that developed AD. There was a significantly positive correlation between the relative abundance of Lachnospiraceae on the skin and CD4⁺ CD25⁺ Foxp3⁺ Treg cells in puppies that became allergic (r = 0.568, P = 0.017).

CONCLUSION AND CLINICAL IMPORTANCE

Further large-scale studies are needed to identify the practical value of these findings in AD diagnosis, treatment and prevention.

House dust endotoxin, asthma and allergic sensitization through childhood into adolescence

Background

House dust endotoxin may have beneficial effects on allergic sensitization and asthma in children. Evidence is scarce for adolescents and most studies so far have been cross‐sectional and limited to a single exposure measurement.

Objective

We assessed associations of house dust endotoxin with asthma and allergic sensitization from birth to age 17 years longitudinally taking into account exposure early in life and at primary school age.

Methods

We used data of 854 participants of the prospective Dutch PIAMA birth cohort study with house dust endotoxin measurements at 3 months and/or 5‐6 years and data on asthma and/or allergic sensitization from at least one of 11 follow‐ups until age 17. We assessed overall and age‐specific associations of the prevalence of asthma and sensitization with mattress and living room floor dust concentrations (per gram of dust) and loads (per m² of sampling surface).

Results

Higher living room floor dust endotoxin concentrations at 3 months were associated with lower odds of asthma until age 4 [odds ratio (95% confidence interval) ranging from 0.70 (0.51‐0.97) at age 1 to 0.76 (0.57‐1.00) at age 3 per interquartile range increase], but not thereafter in children of allergic mothers. Higher living room floor dust endotoxin at 5‐6 years was associated with higher odds of sensitization at 8‐16 years [eg odds ratio (95% confidence interval) 1.70 (1.17‐2.47) per interquartile range increase in endotoxin load].

Conclusions and clinical relevance

House dust endotoxin may have beneficial effects on asthma in preschool children of allergic mothers, which do not persist into adolescence. Beneficial associations with allergic sensitization could not be confirmed.

Early Life Domestic Pet Ownership, and the Risk of Pet Sensitization and Atopic Dermatitis in Preschool Children: A Prospective Birth Cohort in Shanghai

Background: Although domestic pet ownership is on the rise, the impact of early life pet ownership on children's pet sensitization and atopic dermatitis (AD) remains controversial. Methods: Shanghai Allergy Cohort is an ongoing prospective study followed up to the age of 5 years. Pregnant mothers were recruited and their offspring were followed up every year by a group of pediatricians. Information on furred pet ownership was collected by the questionnaire. AD was diagnosed by dermatologists according to disease history and Williams criteria at 5 years ± 1 months. Skin prick test (SPT) was performed to determine sensitization to specific allergens. Multiple logistic regression models were used to evaluate the associations between pet ownership and AD, dog/cat sensitization. Results: In the 538 children at preschool age, 112 (20.82%) were diagnosed with AD. Dermatophagoides pteronyssinus and Dermatophagoides farina were the most common allergens, and almost 10% of children were positive to dog and cat. The percentage of positive SPT reactors at 5-year old was 65.28% in the group of children with AD, higher than that in non-AD group (44.57%). Domestic pet ownership at both infant and preschool period was positively associated with an increased risk of sensitization to dog (OR _adjusted = 2.85 [95% CI: 1.08-7.50 for infant exposure], OR _adjusted = 2.73 [95% CI: 1.33-5.61] for preschool exposure), and interestingly, pet ownership at infant period negatively associated with higher risk of AD at 5-year old (OR adjusted = 0.33 [95% CI: 0.12-0.88]). Conclusion: This is the first prospective birth cohort study in Shanghai that found half of preschool children had positive allergen sensitization even in the non-AD children. Although early life exposure to dog may increase the risk of dog sensitization, it significantly decreased the risk of AD. The underlying mechanisms warrant further investigations.

Associations between evaporative cooling and dust-mite allergens, endotoxins, and β-(1 → 3)-d-glucans in house dust: A study of low-income homes

Recent work suggests that evaporative coolers increase the level and diversity of bioaerosols, but this association remains understudied in low-income homes. We conducted a cross-sectional study of metropolitan, low-income homes in Utah with evaporative coolers (n = 20) and central air conditioners (n = 28). Dust samples (N = 147) were collected from four locations in each home and analyzed for dust-mite allergens Der p1 and Der f1, endotoxins, and β-(1 → 3)-d-glucans. In all sample locations combined, Der p1 or Der f1 was significantly higher in evaporative cooler versus central air conditioning homes (OR = 2.29, 95% CI = 1.05-4.98). Endotoxin concentration was significantly higher in evaporative cooler versus central air conditioning homes in furniture (geometric mean (GM) = 8.05 vs 2.85 EU/mg, P < .01) and all samples combined (GM = 3.60 vs 1.29 EU/mg, P = .03). β-(1 → 3)-d-glucan concentration and surface loads were significantly higher in evaporative cooler versus central air conditioning homes in all four sample locations and all samples combined (P < .01). Our study suggests that low-income, evaporative cooled homes have higher levels of immunologically important bioaerosols than central air-conditioned homes in dry climates, warranting studies on health implications and other exposed populations.

Bovine Allergens in a Ruminant Clinic and Dairy Barns: Exposure Levels, Determinants, and Variability

Background

Dairy farmers may develop specific sensitization and allergic airway diseases due to bovine allergens. However, dose-response relationships are lacking, and as yet little is known on bovine allergen exposure levels.

Objective

To investigate bovine allergen exposure levels in a ruminant clinic and dairy barns, and to assess exposure determinants and variability of exposure.

Methods

Samples were collected using active and passive airborne dust measurements in a ruminant clinic and several dairy barns. Bovine allergen levels were determined by sandwich enzyme-linked immunosorbent assay. Linear mixed models were applied to explore the association between bovine allergen exposure levels and potential exposure determinants. Day-to-day within-worker and between-worker exposure variability was determined, as well as how exposure determinants affect exposure variability.

Results

Bovine allergens were measureable in all samples. Personal bovine allergen exposure levels in the ruminant clinic ranged from 0.10 to 24.8 µg/m3, geometric mean (GM) 1.34 µg/m3. Exposure levels varied dependent on job titles. Personal exposure levels in dairy barns ranged from 0.10 to 46.8 µg/m3, GM 1.47 µg/m3. Type of bedding materials in the barns appeared to be a significant determinant of bovine allergen levels. Compost bedding, particularly, increased allergen levels. Milking by robot was the most important determinant explaining between-worker exposure variability, while bedding was important as well. Bovine allergen levels in stationary measurements were somewhat lower than personal measurements (GM ratio 0.47). Bovine allergens could be readily detected in electrostatic dust-fall collector measurements.

Conclusion

This study provides insight in bovine allergen exposure levels and their determinants, which is a first step to investigate dose-response relationships between sensitization/allergy associated with exposure to bovine allergen levels in future studies.

Maternal exposure to farming environment protects offspring against allergic diseases by modulating the neonatal TLR-Tregs-Th axis

Background

As the development of urbanization in China, the morbidity of allergic disease rise up prominently even in children, which may be partially associated with the excessively clean environment. It has been reported that common microorganism in rural environment shows protective effects on allergic disease by modulating TLRs-Tregs/Th cell axis. But the mechanism of this protection still needs to be elucidated in detail. We investigated the effects of maternal exposure to farming environment on the neonatal innate immune system, especially on the TLR-Treg-Th (Th1, Th2, Th9, and Th17) axis, in the Jilin province of China.

Methods

Eighty-four non-farming and 42 farming pregnant women were recruited. Endotoxins and glucans in dust from the living rooms of the pregnant mothers were measured. Cord blood mononuclear cells were challenged with phytohemagglutinin, lipopolysaccharide, or peptidoglycan. Proliferative response of lymphocyte was measured by 3H-TdR incorporation methods, CD4 + CD25 + FOXP3 + T cells percentage was assessed with flow cytometry, Tregs specific genes (FOXP3, LAG3, GITR, CTLA-4 and TGF-β) and TLR2, TLR4 genes expression were detected by RT-PCR, specific cytokines of Th1, Th2, Th9, Th17 and Tregs were measured with flow cytometer, suppressive capacity of Tregs was tested by culturing with effector cells in vitro, and TLR2/4 gene polymorphism was detected.

Results

Higher endotoxin content was observed in the living rooms of the farming mothers. Compared with that in the non-farming group, in farming neonatal CBMCs, lymphocyte proliferation declined; the IFN-γ/IL-13 ratio increased; and the quantity of Tregs and gene expression of FOXP3, GITR, CTLA4 and TLR2 increased significantly (P < 0.05). Isolated Tregs suppressed the proliferation of effector T cells and IL-13 production more strongly in vitro (P = 0.04, 0.03, respectively), and the TLR2 polymorphism affected FOXP3 expression and IFN-γ and IL-13 production.

Conclusions

Maternal exposure to farming affected the quantity and function of neonatal Tregs upon stimulation with PPG and LPS, which partly contributed to reducing the risk for allergic diseases in the offspring. The results of our study will lay the theoretical foundation for allergic disease prevention in early life.

Electronic supplementary material

The online version of this article (10.1186/s13601-018-0220-0) contains supplementary material, which is available to authorized users.

The association between endotoxin in house dust with atopy and exercise-induced bronchospasm in children with asthma

BACKGROUND

Studies have reported protective and adverse associations between microbial exposure and childhood asthma. However, among children with asthma the relationships between endotoxin and exercise-induced bronchospasm (EIB) is less clear.

OBJECTIVE

We investigated the association between exposure to endotoxin in house dust with atopy and EIB in children with asthma.

METHODS

A cross-sectional survey was conducted among schoolchildren (aged 7-17 years) in the province of Saskatchewan, Canada. A subpopulation with asthma (n = 116) were identified from 335 participants using a validated asthma algorithm. We determined atopy among the asthma subpopulation by skin prick testing (SPT) while EIB was evaluated using exercise challenge testing (ECT). Dust samples were collected from mattress and play area floors, and endotoxin was measured in dust extracts. Logistic regression analyses were used to explore associations between endotoxin with atopy and EIB.

RESULTS

Among the 116 children with asthma, 99 completed SPT and all had completed ECT. Of these, 71/99 (71.7%) were atopic and 26/116 (22.4%) had EIB. Exposure to high play area endotoxin concentration [adjusted odds ratio (aOR) = 0.15, 95% CI: 0.03-0.85] and load (aOR = 0.11, 95% CI: 0.02-0.73) were negatively associated with atopy. In contrast, EIB was positively associated with high mattress endotoxin concentration (aOR = 6.01, 95% CI: 1.20-30.13).

CONCLUSION

Indoor microbial endotoxin exposure has varied associations with atopy and exercise-induced bronchospasm among children with asthma.

An approach to the asthma-protective farm effect by geocoding: Good farms and better farms

BACKGROUND

The highly consistent association of growing up on a farm with a reduced asthma risk has so far been attributed to direct farm exposure. In contrast, geographic determinants of the larger environment have never been assessed. In this study, the effects of proximity to farms and environmental variables in relation to the residential address on asthma and atopy were assessed.

METHODS

Addresses of 2265 children of the Bavarian arm of the GABRIELA study were converted into geocodes. Proximity to the nearest cow farm was calculated, and environmental characteristics were derived from satellite data or terrestrial monitoring. Bacterial diversity in mattress dust samples was assessed in 501 children by sequencing of the 16S rRNA amplicons. Logistic regression models were used to calculate associations between outcomes and exposure variables.

RESULTS

Asthma and atopy were inversely associated with the presence of a farm within a radius of maximum 100 m. The environmental variables greenness, tree cover, soil sealing, altitude, air pollution differed not only between farm and non-farm children but also between farm children with and without another farm nearby. The latter distinction revealed strong associations with characteristics of traditional farms including a broader diversity of microbial exposure, which mainly contributed to the protective effect on asthma. In non-farm children, the protective effect of a farm nearby was completely explained by consumption of farm milk.

CONCLUSIONS

Clustering of farms within a neighborhood of 100 m is strongly associated with the protective effect on asthma and may represent a more traditional style of farming with broader microbial exposure.

Quantitative assessment of microbes from samples of indoor air and dust

Different types of house dust samples are widely used as surrogates of airborne inhalation exposure in studies assessing health effects of indoor microbes. Here we studied-in a quantitative assessment-the representativeness of different house dust samples of indoor air (IA) and investigated seasonality and reproducibility of indoor samples. Microbial exposure was measured five times over 1 year in four rural and five urban Finnish homes. Six sampling methods were used: button inhalable aerosol sampler (actively collected personal and indoor air sampling), settled dust, floor dust, mattress dust and vacuum cleaner dust bag dust; the latter three referred to herein as "reservoir dust samples". Using quantitative PCR, we quantified the fungal species Cladosporium herbarum, the fungal group Penicillium/Aspergillus/Paecilomyces variotii, total fungal DNA, and Gram-positive and Gram-negative bacteria. We observed significant differences in microbial levels between rural and urban homes, most pronounced for personal air samples. Fungal species and groups but not total fungal DNA in indoor air correlated moderately to well with reservoir dust and with personal air samples. For bacterial groups, the correlations between air and dust were generally lower. Samples of indoor air and settled dust reflected similarly seasonal variation in microbial levels and were also similar compositionally, as assessed by ratios of qPCR markers. In general, determinations from mattress dust and other reservoir samples were better reproducible in repeated assessments over time than from indoor air or settled dust. This study indicates that settled dust reflects the microbial composition of indoor air and responds similarly to environmental determinants. Reservoir dusts tend to predict better microbial levels in indoor air and are more reproducible. Sampling strategies in indoor studies need to be developed based on the study questions and may need to rely on more than one type of sample.

Pediatric Asthma and the Indoor Microbial Environment

The global increase in the prevalence of asthma has been related to several risk factors; many of them linked to the "westernization" process and the characteristics of the indoor microbial environment during early life may play an important role. Living in moisture damaged homes contributes to the exacerbation and development of asthma. However, living in homes with a rich variety and high levels of microbes (e.g., traditional farming environments) may confer protection. While the results of previous research are rather consistent when it comes to observation/report of indoor moisture damage or when comparing farming versus non-farming homes, when actual measures targeting indoor microbial exposure are included, the picture becomes less clear and the associations appear inconsistent. This may partly be due to limitations of sampling and measurement techniques that make comparisons difficult and provide an incomplete picture of the indoor microbial environment and in particular also human exposure. In this regard, new generation sequencing techniques represent a potential revolution in better understanding the impact of the indoor microbiome on human health.

Differential effects of air conditioning type on residential endotoxin levels in a semi-arid climate

Residential endotoxin exposure is associated with protective and pathogenic health outcomes. Evaporative coolers, an energy-efficient type of air conditioner used in dry climates, are a potential source of indoor endotoxins; however, this association is largely unstudied. We collected settled dust biannually from four locations in homes with evaporative coolers (n=18) and central air conditioners (n=22) in Utah County, Utah (USA), during winter (Jan-Apr) and summer (Aug-Sept), 2014. Dust samples (n=281) were analyzed by the Limulus amebocyte lysate test. Housing factors were measured by survey, and indoor temperature and relative humidity measures were collected during both seasons. Endotoxin concentrations (EU/mg) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons. Endotoxin surface loads (EU/m² ) were significantly higher in homes with evaporative coolers from mattress and bedroom floor samples during both seasons and in upholstered furniture during winter. For the nine significant season-by-location comparisons, EU/mg and EU/m² were approximately three to six times greater in homes using evaporative coolers. A plausible explanation for these findings is that evaporative coolers serve as a reservoir and distribution system for Gram-negative bacteria or their cell wall components in homes.

Allergic disease in 8-year-old children is preceded by delayed B cell maturation

BACKGROUND

We previously reported that exposure to a farming environment is allergy-protective, while high proportions of neonatal immature/naïve CD5⁺ B cells and putative regulatory T cells (Tregs) are risk factors for development of allergic disease and sensitization up to 3 years of age.

OBJECTIVE

To examine if B and T cell maturation are associated with allergic disease and farming environment over the first 8 years in life.

METHODS

In the prospective FARMFLORA study, including both farming and non-farming families, 48 of 65 children took part in the 8-year follow-up study. Various B and T cell maturation variables were examined in blood samples obtained at several occasions from birth to 8 years of age and related to doctors' diagnosed allergic disease and sensitization, and to farming environment.

RESULTS

We found that the incidence of allergic disease was lower among farmers' compared to non-farmers' children during the 8-year follow-up period, and that farmers' children had higher proportions of memory B cells at 8 years of age. Moreover, a high proportion of neonatal CD5⁺ B cells was a risk factor for and may predict development of allergic disease at 8 years of age. A high proportion of Tregs was not protective against development of these conditions.

CONCLUSION AND CLINICAL RELEVANCE

High proportions of neonatal naïve B cells remained as a risk factor for allergic disease in school-aged children. Thus, the accelerated B cell maturation observed among farmers' children may be crucial for the allergy-protective effect of a farming environment.

Are Cockroaches an Important Source of Indoor Endotoxins?

Endotoxins are common indoor biocontaminants. Their levels have been shown to link to many sources and factors. One of them is cockroach infestation but the role of cockroaches and contamination mechanisms are unclear. We hypothesized that not only is cockroach infestation a sign of poor hygiene, but it also contributes to indoor endotoxins via fecal contamination. In this study, different cockroach species were caught in homes. The endotoxin and allergen levels and their ratios in cockroach feces were determined. To estimate the amount of indoor endotoxins that originated from cockroaches, a new approach of using these new cockroach endotoxin and allergen ratios to compare with environmental data was employed. We found that Supella (S.) longipalpa, Periplaneta (P.) australasiae, and Blattella (B.) germanica were dominant in homes. On average, P. australasiae feces had a higher level but greater variation of endotoxins. B. germanica feces had the highest levels of allergens measured. Depending on environmental bacterial load and the type of cockroaches present, cockroach endotoxins in the environment may vary greatly. Cockroaches directly contribute to indoor endotoxins rather than just being a sign of poor hygiene. The type and extent of cockroach infestation should be taken into consideration when assessing and remediating indoor endotoxin contamination.

Maternal allergic disease history affects childhood allergy development through impairment of neonatal regulatory T-cells

BACKGROUND

Maternal allergic disease history and impaired regulatory T-cells (Tregs) are critical risk factors for allergy development in children. However, the mechanisms that underlie these risk factors remain poorly defined. Therefore, the aim of this study was to assess whether maternal allergies affect the Tregs of offspring and lead to allergy development in childhood.

METHODS

A total of 332 mothers of healthy newborns (234 from no allergic mothers, 98 from allergic mothers) were recruited to this study. Detailed questionnaires were administered yearly to determine the allergy status of the mothers and the newborns from birth to 3 years of age. Cord blood samples obtained at the time of birth were analysed for Treg counts, as well Treg activity, based on their response to Toll-like receptor (TLR) stimuli such as lipid A (LPA) and peptidoglycans (PPG). Surface markers, associated genes, suppressive capacity, and cytokine levels of Tregs were also measured. Possible correlations between Treg activity and maternal or neonate allergies were assessed. In addition, environmental microbial content and other known risk factors for allergies were measured.

RESULTS

Cord blood mononuclear cells (CBMCs) from offspring with allergic mothers showed fewer CD4(+)CD25(+)FOXP3(+) T cells, lower expression levels of associated genes, and reduced cytokine production of interleukin (IL)-10 and interferon-γ (P < 0.05), especially via the PPG-TLR2 pathway. Suppression of effector T cells by Tregs from children of mothers with allergies was impaired, especially IL-13 production by Type 2 T helper (Th2) cells (P = 0.026). Children who developed allergies in the first 3 years of life had lower numbers of CD4(+)CD25(+)FOXP3(+) T cells and reduced FOXP3 expression and IL-10 production as newborns (P < 0.05). Maternal allergic background was identified as a risk factor for allergy development in the children (Odds ratio (OR) = 2.46, 95 % CI = 1.05-5.79); while declining Treg numbers, IL-10 production, and FOXP3 expression in neonates (PPG and LPA stimulated) were identified as independent risk factors for allergic diseases in offspring at 3 years of age after adjusting for maternal allergic history and environmental factors (P < 0.05).

CONCLUSION

Maternal allergy correlated with impaired Tregs in neonates, and this could enhance the susceptibility of offspring to allergic diseases in early childhood due to an imbalance of Th1 and Th2 cells.

Allergy protection by cowshed bacteria - recent findings and future prospects

Since the first publication in 1999, numerous epidemiologic studies provided strong evidence that frequent contact to a traditional farm environment in early life protects children from the development of allergic airway diseases. These consistent findings prompted enormous efforts to identify and characterize the potential causative factors and the underlying immunologic mechanisms in experimental studies. The cumulating evidence for the role of the cowshed-associated bacterial flora led to enhanced efforts not only to identify the relevant species but also to examine their specific immunomodulatory capacity, the bacterial components involved, and particularly the cellular and molecular mechanisms of their interaction with the immune system. We review here the methods applied to identify relevant bacterial species, the species which emerged thereof, and the similarities and differences in their mode of action as revealed so far. We further consider the impact of the current knowledge on worthwhile clinical application and reflect on the required next steps to foster the translation of the encouraging scientific progress which has been made in recent years.

Exposure to high endotoxin concentration increases wheezing prevalence among laboratory animal workers: a cross-sectional study

Background

Endotoxin from Gram-negative bacteria are found in different concentrations in dust and on the ground of laboratories dealing with small animals and animal houses.

Methods

Cross-sectional study performed in workplaces of two universities. Dust samples were collected from laboratories and animal facilities housing rats, mice, guinea pigs, rabbits or hamsters and analyzed by the “Limulus amebocyte lysate” (LAL) method. We also sampled workplaces without animals. The concentrations of endotoxin detected in the workplaces were tested for association with wheezing in the last 12 months, asthma defined by self-reported diagnosis and asthma confirmed by bronchial hyperresponsiveness (BHR) to mannitol.

Results

Dust samples were obtained at 145 workplaces, 92 with exposure to animals and 53 with no exposure. Exposed group comprised 412 subjects and non-exposed group comprised 339 subjects. Animal-exposed workplaces had higher concentrations of endotoxin, median of 34.2 endotoxin units (EU) per mg of dust (interquartile range, 12.6–65.4), as compared to the non-exposed group, median of 10.2 EU/mg of dust (interquartile range, 2.6–22.2) (p < 0.001). The high concentration of endotoxin (above whole sample median, 20.4 EU/mg) was associated with increased wheezing prevalence (p < 0.001), i.e., 61 % of workers exposed to high endotoxin concentration reported wheezing in the last 12 months compared to 29 % of workers exposed to low endotoxin concentration. The concentration of endotoxin was not associated with asthma report or with BHR confirmed asthma.

Conclusion

Exposure to endotoxin is associated with a higher prevalence of wheezing, but not with asthma as defined by the mannitol bronchial challenge test or by self-reported asthma. Preventive measures are necessary for these workers.

Earlier infantile immune maturation is related to higher DTP vaccine responses in children

There are large inter-individual variations in vaccine-specific antibody responses in children. We sought to investigate whether early-life environmental factors and/or adaptive immune maturation were related to diphtheria–tetanus–pertussis (DTP) vaccine-specific antibody levels at 18 months of age. In the prospective FARMFLORA birth-cohort, including both farming and non-farming families, children were immunized with DTP vaccine at 3, 5 and 12 months of age. DTP vaccine-induced antibody levels were measured in plasma at 18 months of age. Infants' blood samples obtained at birth, 3–5 days, 4, 18 and 36 months and at 8 years of age were analyzed for total CD4⁺ T- and B-cell counts, proportions of naïve and memory T and B cells, and fractions of putative regulatory T cells by flow cytometry. Multivariate factor analysis was used to examine associations between immune variables and vaccine responses. The most apparent multivariate pattern was that higher anti-DTP antibody titers at 18 months of age were associated with lower infantile total counts of T and B cells in the blood. Furthermore, lower infantile total T- and B-cell blood counts were associated with higher proportions of circulating CD45RO⁺ memory T cells and to lower proportions of α4β7⁺ naïve T cells later in childhood. The multivariate findings were corroborated in univariate correlation analyses. Sex, delivery mode and dairy farm exposure were unrelated to the magnitude of DTP-specific antibody responses. Our results thus suggest that children with a more mature/activated infantile adaptive immunity respond with higher vaccine-induced anti-DTP antibody levels at 18 months of age.

Cow allergen (Bos d2) and endotoxin concentrations are higher in the settled dust of homes proximate to industrial-scale dairy operations

Airborne contaminants produced by industrial agricultural facilities contain chemical and biological compounds that can impact the health of residents living in close proximity. Settled dust can be a reservoir for these contaminants and can influence long-term exposures. In this study, we sampled the indoor- and outdoor-settled dust from 40 homes that varied in proximity to industrial-scale dairies (ISD; industrial-scale dairy, a term used in this paper to describe a large dairy farm and adjacent waste sprayfields, concentrated animal feeding operation or animal feeding operation, that uses industrial processes) in the Yakima Valley, Washington. We analyzed settled dust samples for cow allergen (Bos d2, a cow allergen associated with dander, hair, sweat and urine, it is a member of the lipocalin family of allergens associated with mammals), mouse allergen (Mus m1; major mouse allergen, a mouse urinary allergen, in the lipocalin family), dust mite allergens (Der p1 (Dermatophagoides pteronissinus 1) and Der f1 (Dermatophagoides farinae 1)), and endotoxin (a component of the cell walls of gram negative bacteria, lipopolysaccharide, which can be found in air and dust and can produce a strong inflammatory response). A concentration gradient was observed for Bos d2 and endotoxin measured in outdoor-settled dust samples based on proximity to ISD. Indoor-settled dust concentrations of Bos d2 and endotoxin were also highest in proximal homes. While the associated health effects of exposure to cow allergen in settled dust is unknown, endotoxin at concentrations observed in these proximal homes (100 EU/mg) has been associated with increased negative respiratory health effects. These findings document that biological contaminants emitted from ISDs are elevated in indoor- and outdoor-settled dust samples at homes close to these facilities and extend to as much as three miles (4.8 km) away.

Determinants of house dust, endotoxin, and β-(1→3)-D-glucan in homes of Danish children

Little is known about the geographic variation and determinants of bacterial endotoxin and β-(1,3)-D-glucan in Danish house dust. In a population of 317 children, we: (i) described loads and concentrations of floor dust, endotoxin, and β-(1→3)-D-glucan and (ii) their correlations and (iii) assessed their determinants; (iv) Finally, we compared our findings with previous European studies. Bedroom floor dust was analyzed for endotoxin content by the kinetic limulus amoebocyte lysate assay and for β-(1→3)-D-glucan by the inhibition enzyme immunoassay. The parents answered questions regarding potential determinants. We found: geometric means (geometric standard deviations) 186 mg/m(2) (4.3) for dust; 5.46 × 10(3) EU/m(2) (8.0) and 31.1 × 10(3) EU/g (2.6) for endotoxin; and 142 μg/m(2) (14.3) and 0.71 × 10(3) μg/g (7.3) for β-(1→3)-D-glucan. High correlations (r > 0.75) were found between floor dust and endotoxin and β-(1→3)-D-glucan loads, while endotoxin and β-(1→3)-D-glucan concentrations were moderately correlated (r = 0.36-0.41) with the dust load. Having a carpet was positively associated with dust load and with endotoxin and β-(1→3)-D-glucan concentrations. Pet keeping, dwelling type, and dwelling location were determinants of endotoxin concentrations. No other determinants were associated with β-(1→3)-D-glucan concentrations. Compared with other European studies, we found lower β-(1→3)-D-glucan loads and concentrations but higher endotoxin loads and concentrations suggesting a geographically determined different composition of Danish floor dust compared with other European regions.

Determinants, reproducibility, and seasonal variation of bacterial cell wall components and viable counts in house dust

The objectives of this study were (i) to assess the determinants that affect concentrations of the bacterial cell wall components 3-hydroxy fatty acids (3-OH FAs) and muramic acid and of total viable bacteria and actinomycetes in house dust; and (ii) to examine the seasonal variation and reproducibility of these bacterial cell wall components in house dust. A number of lifestyle and environmental factors, mostly not consistent for different bacterial measures but commonly including the type of dwelling and farming (number of livestock), explained up to 37% of the variation of the bacterial concentrations in 212 homes in Eastern Finland. The reproducibility of 3-OH FAs and muramic acid measurements in house dust were studied in five urban homes and were found to be generally high (ICC 74-84%). Temporal variation observed in repeated sampling of the same home throughout a year was more pronounced for 3-OH FAs determinations (ICC 22%) than for muramic acid (ICC 55-66%). We conclude that determinants vary largely for different types of bacterial measurements in house dust; the measured parameters represent different aspects of the bacterial content indoors. More than one sample is needed to describe bacterial concentrations in house dust in the home environment due to large temporal variation.

Predictors of microbial agents in dust and respiratory health in the Ecrhs

Background

Dampness and mould exposure have been repeatedly associated with respiratory health. However, less is known about the specific agents provoking or arresting health effects in adult populations. We aimed to assess predictors of microbial agents in mattress dust throughout Europe and to investigate associations between microbial exposures, home characteristics and respiratory health.

Methods

Seven different fungal and bacterial parameters were assessed in mattress dust from 956 adult ECRHS II participants in addition to interview based home characteristics. Associations between microbial parameters and the asthma score and lung function were examined using mixed negative binomial regression and linear mixed models, respectively.

Results

Indoor dampness and pet keeping were significant predictors for higher microbial agent concentrations in mattress dust. Current mould and condensation in the bedroom were significantly associated with lung function decline and current mould at home was positively associated with the asthma score. Higher concentrations of muramic acid were associated with higher mean ratios of the asthma score (aMR 1.37, 95%CI 1.17-1.61). There was no evidence for any association between fungal and bacterial components and lung function.

Conclusion

Indoor dampness was associated with microbial levels in mattress dust which in turn was positively associated with asthma symptoms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-015-0042-y) contains supplementary material, which is available to authorized users.

Higher B-cell activating factor levels at birth are positively associated with maternal dairy farm exposure and negatively related to allergy development

BACKGROUND

A high proportion of circulating immature/naive CD5(+) B cells during early infancy is a risk factor for allergy development. B-cell activating factor (BAFF) is an important cytokine for B-cell maturation.

OBJECTIVE

We sought to investigate whether BAFF levels are related to environmental exposures during pregnancy and early childhood and whether BAFF levels are associated with postnatal B-cell maturation and allergic disease.

METHODS

In the FARMFLORA study, including both farming and nonfarming families, we measured BAFF levels in plasma from mothers and their children at birth and at 1, 4, 18, and 36 months of age. Infants' blood samples were also analyzed for B-cell numbers and proportions of CD5(+) and CD27(+) B cells. Allergic disease was clinically evaluated at 18 and 36 months of age.

RESULTS

Circulating BAFF levels were maximal at birth, and farmers' children had higher BAFF levels than nonfarmers' children. Higher BAFF levels at birth were positively associated with proportions of CD27(+) memory B cells among farmers' children and inversely related to proportions of CD5(+) immature/naive B cells among nonfarmers' children. Children with allergic disease at 18 months of age had lower cord blood BAFF levels than nonallergic children. At birth, girls had higher BAFF levels and lower proportions of CD5(+) B cells than boys.

CONCLUSIONS

Farm exposure during pregnancy appears to induce BAFF production in the newborn child, and high neonatal BAFF levels were associated with more accelerated postnatal B-cell maturation, which lend further strength to the role of B cells in the hygiene hypothesis.

Indoor allergens in settled dust from kindergartens in city of Łódź, Poland

OBJECTIVES

The main objective of the study was to determine the levels of house dust mite (Der p1), dog (Can f1), cat (Fel d1) and cockroach (Bla g2) allergens in kindergartens localized in an urban agglomeration.

MATERIAL AND METHODS

A quantitative analysis of allergens was carried out in settled dust samples collected by vacuuming the floor surface in three kindergartens (N = 84) and children's clothing (N = 36). The samples were collected in spring-summer and autumn-winter periods as well as at the beginning and end of the week. The allergen dust concentration was determined by enzyme-linked immunoenzymatic assay (ELISA).

RESULTS

The mean geometric concentrations (±geometric standard deviations) of allergens Der p1, Can f1, Fel d1 and Bla g2 determined in kindergartens were: 0.02 ± 3.21 μg/g of dust; 0.97 ± 4.49 μg/g of dust; 0.30 ± 4.43 μg/g of dust and 0.01 ± 3.08 μg/g of dust, respectively. Younger classrooms (children aged from 3 to 4 years) were characterized by almost twice higher mean concentration of allergen Fel d1, as compared to older classrooms (children aged from 5 to 6 years) (p < 0.05). A significant impact of seasonality on the level of dog allergen Can f1 was found (p < 0.05). No significant weekly variation was found in average concentrations of the allergens. Children who had a dog and/or cat at home were characterized by high concentrations of allergens Can f1 and Fel d1 on their clothes (59.2 ± 5.39 μg Can f1/g of dust; 3.63 ± 1.47 μg Fel d1/g of dust), significantly higher than concentrations of allergens in children who did not have any pets (p < 0.001).

CONCLUSIONS

Special attention should be paid to keeping the kindergarten rooms tidy and clean and to an appropriate choice of furnishings and fittings which would prevent the proliferation of the house dust mite and accumulation of allergens.

Quantity and diversity of environmental microbial exposure and development of asthma: a birth cohort study

Background

Early-life exposure to environmental microbial agents may be associated with the development of allergies. The aim of the study was to identify better ways to characterize microbial exposure as a predictor of respiratory symptoms and allergies.

Methods

A birth cohort of 410 children was followed up until 6 years of age. Bacterial endotoxin, 3-hydroxy fatty acids, N-acetyl-muramic acid, fungal extracellular polysaccharides (EPS) from Penicillium and Aspergillus spp., β-D-glucan, ergosterol, and bacterial or fungal quantitative polymerase chain reactions (qPCRs) were analyzed from dust samples collected at 2 months of age. Asthma, wheezing, cough, and atopic dermatitis were assessed using repeated questionnaires. Specific IgEs were determined at the age of 1 and 6 years.

Results

Only few associations were found between single microbial markers and the studied outcomes. In contrast, a score for the total quantity of microbial exposure, that is, sum of indicators for fungi (ergosterol), Gram-positive (muramic acid) bacteria, and Gram-negative (endotoxin) bacteria, was significantly (inverted-U shape) associated with asthma incidence (P < 0.001): the highest risk was found at medium levels (adjusted odds ratio (aOR) 2.24, 95% confidence interval (95% CI) 0.87–5.75 for 3rd quintile) and the lowest risk at the highest level (aOR 0.34, 95% CI 0.09–1.36 for 5th quintile). The microbial diversity score, that is, sum of detected qPCRs, was inversely associated with risk of wheezing and was significantly (inverted-U shape) associated with sensitization to inhalant allergens.

Conclusion

Score for quantity of microbial exposure predicted asthma better than single microbial markers independently of microbial diversity and amount of dust. Better indicators of total quantity and diversity of microbial exposure are needed in studies on the development of asthma.

Effectiveness of interventions to reduce flour dust exposures in supermarket bakeries in South Africa

RATIONALE

A recent study of supermarket bakery workers in South Africa demonstrated that 25% of workers were sensitised to flour allergens and 13% had baker's asthma. Evidence on exposure reduction strategies using specifically designed interventions aimed at reducing the risk of baker's asthma is scarce.

OBJECTIVES

The aim of this study was to evaluate the effectiveness of different control measures to reduce airborne flour dust exposure using a randomised design.

METHODS

A group-randomised study design was used to assign 30 bakeries of a large supermarket chain store to two intervention groups and a control group, of which 15 bakeries were studied. Full-shift environmental personal samples were used to characterise exposure to flour dust and wheat and rye allergens levels pre-intervention (n=176) and post-intervention (n=208).

RESULTS

The overall intervention effect revealed a 50% decrease in mean flour dust, wheat and rye allergen exposure. The reduction in exposure was highest for managers (67%) and bakers (47%), and lowest for counterhands (23%). For bakers, the greatest reduction in flour dust was associated with control measures such as the use of the mixer lid (67%), divider oil (63%) or focused training (54%). However, the greatest reduction (80%) was observed when using a combination of all control measures.

CONCLUSIONS

A specially designed intervention strategy reduced both flour dust and allergen levels. Best results were observed when combining both engineering controls and training. Further studies will investigate the long-term health impact of these interventions on reducing the disease burden among this group of bakers.

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 child's bedroom. We examined the relationship between these fungal agents and degree of parent or inspector-reported home indoor dampness, and microbiological laboratory's 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.

Dampness and moulds in relation to respiratory and allergic symptoms in children: results from Phase Two of the International Study of Asthma and Allergies in Childhood (ISAAC Phase Two)

BACKGROUND

Many studies report that damp housing conditions are associated with respiratory symptoms. Less is known about mechanisms and possible effect modifiers. Studies of dampness in relation to allergic sensitization and eczema are scarce.

OBJECTIVE

We study the influence of damp housing conditions world-wide on symptoms and objective outcomes.

METHODS

Cross-sectional studies of 8-12-year-old children in 20 countries used standardized methodology from Phase Two of the International Study of Asthma and Allergies in Childhood (ISAAC). Symptoms of asthma, rhinitis and eczema, plus residential exposure to dampness and moulds, were ascertained by parental questionnaires (n = 46 051). Skin examination, skin prick tests (n = 26 967) and hypertonic saline bronchial challenge (n = 5713) were performed. In subsamples stratified by wheeze (n = 1175), dust was sampled and analysed for house dust mite (HDM) allergens and endotoxin.

RESULTS

Current exposure to dampness was more common for wheezy children (pooled odds ratio 1.58, 95% CI 1.40-1.79) and was associated with greater symptom severity among wheezers, irrespective of atopy. A significant (P < 0.01) adverse effect of dampness was also seen for cough and phlegm, rhinitis and reported eczema, but not for examined eczema, nor bronchial hyperresponsiveness. HDM sensitization was more common in damp homes (OR 1.16, 1.03-1.32). HDM-allergen levels were higher in damp homes and were positively associated with HDM-sensitization, but not wheeze.

CONCLUSION

A consistent association of dampness with respiratory and other symptoms was found in both affluent and non-affluent countries, among both atopic and non-atopic children. HDM exposure and sensitization may contribute, but the link seems to be related principally to non-atopic mechanisms.

Early life microbial exposure and fractional exhaled nitric oxide in school-age children: a prospective birth cohort study

BACKGROUND

Inflammation is a key factor in the pathogenesis of respiratory diseases. Early life exposure to microbial agents may have an effect on the development of the immune system and on respiratory health later in life.In the present work we aimed to evaluate the associations between early life microbial exposures, and fractional exhaled nitric oxide (FeNO) at school age.

METHODS

Endotoxin, extracellular polysaccharides (EPS) and β(1,3)-D-glucan were measured in living room dust collected at 2-3 months of age in homes of participants of three prospective European birth cohorts (LISA, n = 182; PIAMA, n = 244; and INMA, n = 355). Home dampness and pet ownership were periodically reported by the parents through questionnaires. FeNO was measured at age 8 for PIAMA and at age 10/11 for LISA and INMA. Cohort-specific associations between the indoor microbial exposures and FeNO were evaluated using multivariable regression analyses. Estimates were combined using random-effects meta-analyses.

RESULTS

FeNO at school age was lower in children exposed to endotoxin at age 2-3 months (β -0.05, 95% confidence interval (CI) -0.10;-0.01) and in children with reported dog ownership during the first two years of life (GM ratio 0.82, CI 0.70-0.96). FeNO was not significantly associated with early life exposure to EPS, β(1,3)-D-glucan, indoor dampness and cat ownership.

CONCLUSION

Early life exposure to bacterial endotoxin and early life dog ownership are associated with lower FeNO at school age. Further studies are needed to confirm our results and to unravel the underlying mechanisms and possible clinical relevance of this finding.

The pathophysiology of the hygiene hypothesis

There has been a considerable increase in the diagnosis of allergic diseases over the last decades. Prevalence of allergies in high-income countries and urban areas appears higher than in rural environments. While environmental factors like pollution or nutrition can be important, it is more likely that in the end they have a small association with allergies. Childhood infections and exposure to certain microbial antigens on the other hand seem to present a strong negative correlation with allergies, and therefore the increase of the allergic burden in the Western world has been frequently related to a decline of childhood infections giving birth to the "Hygiene Hypothesis". We address the issue with emphasis on the associated pathophysiology tightrope walking between the skepticism of the critics, which cast doubt on it, and the pilgrims' belief of having discovered allergy's Holy Grail.

Endotoxin, extracellular polysaccharides, and β(1-3)-glucan concentrations in dust and their determinants in four European birth cohorts: results from the HITEA project

Early-life exposure to microbial agents may play a protective role in asthma and allergies development. Geographical differences in the prevalence of these diseases exist, but the differences in early-life indoor microbial agent levels and their determinants have been hardly studied. We aimed to describe the early-life levels of endotoxin, extracellular polysaccharides (EPS), and β(1-3)-glucans in living room dust of four geographically spread European birth cohorts (LISA in Germany, PIAMA in the Netherlands, INMA in Spain, and LUKAS2 in Finland) and to assess their determinants. A total of 1572 dust samples from living rooms of participants were analyzed for endotoxin, Penicillium/Aspergillus EPS, and β(1-3)-glucans. Information on potential determinants was obtained through questionnaires. Concentrations of endotoxin, EPS, and β(1-3)-glucans were different across cohorts. Concentrations of endotoxin and EPS were respectively lower and higher in INMA than in other cohorts, while glucans were higher in LUKAS2. Season of sampling, dog ownership, dampness, and the number of people living at home were significantly associated with concentrations of at least one microbial agent, with heterogeneity of effect estimates of the determinants across cohorts. In conclusion, both early-life microbial exposure levels and exposure determinants differ across cohorts derived from diverse European countries.

PRACTICAL IMPLICATIONS

This study adds evidence of variability in the levels of indoor endotoxin, extracellular polysaccharide, and β(1-3)-glucans across four geographically spread European regions. Furthermore, we observed heterogeneity across regions in the effect of exposure determinants. We hypothesize that the variations observed in our study may play a role in the differences in asthma and allergies prevalences across countries.

Relationships between molds and asthma suggesting non-allergic mechanisms. A rural-urban comparison

BACKGROUND

A fungal index, based on specific microbial volatile organic compounds (MVOCs) emission, was employed and related to asthma in children from rural and urban dwellings after stratification on the children atopic status.

METHODS

A nested case-control design was used to draw, from 2 cross-sectional surveys, 20 asthmatics and 26 controls living in urban areas, and 24 asthmatics and 25 controls in rural areas. MVOCs levels were assessed in the living-room during one week; during that week, children performed clinical tests and their parents were invited to fill in a questionnaire on respiratory health.

RESULTS

According to the objective fungal index, 70.5% of cases and 49.0% of controls were exposed to molds. More children with current asthma had experienced mold exposure in their homes (OR=3.38, 95% CI (1.16; 9.90)), especially amongst children living in rural areas. Atopic status modified this association: exposure to molds was found to be related to current asthma only in non-atopic children (OR=10.42, 95% CI (2.42; 44.81)). Among urban -dwelling children that could be screened at hospital, asthmatic children living in contaminated dwellings had a higher proportion of blood neutrophils and a lower FEV1 (forced expiratory volume in 1 second) than non-exposed ones.

CONCLUSION

Our findings based on an objective assessment of MVOCs suggest adverse respiratory effects of molds. Our results suggest that when looking at the aetiology of non-atopic asthma, mold exposure should be systematically assessed.

Exposure to microbial agents in house dust and wheezing, atopic dermatitis and atopic sensitization in early childhood: a birth cohort study in rural areas

BACKGROUND

Early-life exposure to environmental microbial agents may be associated with development of wheezing and allergic diseases.

OBJECTIVE

To assess the association of microbial exposure in rural homes with the risk of asthma, wheezing, atopic dermatitis and sensitization.

METHODS

Birth cohorts of rural children (n = 1133), half from farmer families, were followed up from birth to 2 years of age by questionnaires in five European centres. Endotoxin and extracellular polysaccharides (EPS) of Penicillium and Aspergillus spp. were determined from living room floor and mother's mattress dust samples collected at 2 months of age. Specific IgE against 19 allergens was measured at 1 year of age. Discrete-time hazard models, generalized estimations equations (GEE) and logistic regression were used for statistical analyses.

RESULTS

The incidence of asthma was inversely associated with the amount of dust (adjusted odds ratio (aOR) 0.73, 95% CI 0.58-0.93) and the loads (units/m(2)) of EPS (aOR 0.75, 95% CI 0.55-1.04) and endotoxin (aOR 0.79, 95% CI 0.60-1.05) in the mother's mattress. Similar associations were seen with wheezing and with living room floor dust. The microbial markers were highly correlated and their effects could not be clearly separated. The inverse associations were seen especially among non-farmers. The risk of sensitization to inhalant allergens increased with increasing endotoxin exposure from mattress dust. No associations were observed with concentrations (units/g) or with atopic dermatitis.

CONCLUSION AND CLINICAL RELEVANCE

The amount and microbial content of house dust were inversely associated with asthma and wheezing, but due to high correlations between microbial agents and amount of dust, it was not possible to disentangle their individual effects. New ways to better measure and represent exposure to environmental microbes, including indexes of biodiversity, are needed especially among farmers.

Microbiological evaluation of ten French archives and link to occupational symptoms

Fungi that damage documents in archives may harm workers' health, depending on which mold species are inhaled, the concentrations of fungal species inhaled, and individual factors. Our aim was to identify and quantify fungi in archives and to investigate possible links with the symptoms experienced by workers. Ten French archives were sampled using an air impactor and electrostatic dust collectors. Allergies and general symptoms felt by 144 workers were reported using a self-report questionnaire. Utilizing culture-based analysis methods along with qPCR, Penicillium chrysogenum, Cladosporium sphaerospermum, and Aspergillus versicolor were the three main fungi in air and dust in terms of quantity and frequency. Median fungal concentrations in storage areas, ranged from 30 to 465 CFU/m(3). People working in the most contaminated archives did not report more symptoms of allergy than others. However, workers in contact with moldy documents reported more headaches (odds ratio, 2.4; 95% confidence interval, 1.1-5.3), fatigue (OR, 2.9; 95% CI, 1.2-6.7), eye irritation (OR, 5.4; 95% CI, 1.9-14.9), throat irritation (OR, 2.4; 95% CI, 1.0-5.7), coughing (OR, 3.2; 95% CI, 1.2-8.4), and rhinorrhea (OR, 2.6; 95% CI, 1.0-6.4) than others. Other parameters such as dust levels and concentrations of metabolites and chemical substances should be considered as confounding factors in further investigations to isolate the role of molds.

PRACTICAL IMPLICATIONS

Most studies about fungi and archives deal with the conservation of manuscripts and documents, and few discuss workers' health problems. Our study shows that archives do not represent a highly contaminated environment. Symptoms felt by workers were more often linked to direct contact with moldy documents than to high concentrations of mold in the air of archive storage areas. This study provides data on concentration levels in archives that could be used to interpret microbiological investigations in this type of environment in the future.

Environmental bacteria and childhood asthma

BACKGROUND

We have previously found an inverse association of bacterial diversity with childhood asthma. It remains unclear whether certain bacteria account for the protective effect.

METHODS

The high variability of the bacterial 16S rRNA gene allows assessing diversity and specificity of bacterial communities by single-strand configuration polymorphism (SSCP). DNA was extracted from mattress dust samples of 489 school-age children from rural and suburban regions in Germany. A fragment of the bacteria-specific 16S rRNA gene was amplified by PCR, digested to single-strand DNA, and subjected to electrophoresis. The resulting band patterns reflect the underlying DNA sequences. The individual bands were tested for associations with asthma, hay fever, and atopy in quantitative and qualitative multivariable analyses. Significantly associated bands were isolated and sequenced. The sequences were compared to a database, and distinct bacteria were identified.

RESULTS

Seven of 76 independent bands were found to be inversely associated with asthma, atopic sensitization, and hay fever with odds ratios ranging from 0.17 to 0.73. The bands contained the sequences of Acinetobacter sp., Lactobacillus spp., Neisseria spp., Staphylococcus sciuri, Jeotgalicoccus sp., Corynebacterium spp., and others.

CONCLUSIONS

In a diverse microbial environment, certain bacteria may account for the protective effect on the development of asthma and atopy.

Sampling, extraction and measurement of bacteria, endotoxin, fungi and inflammatory potential of settling indoor dust

Selection of sampling device, sampling location and period are important first steps in the measurement of exposure to bioaerosols in indoor air. The steps following the sampling include treatment of samples and laboratory analysis. In this study, settling bacteria, endotoxin, fungi and serine protease have been measured in Danish homes using Electrostatic Dust Fall Collectors (EDCs). The effects of the presence of occupants, sampling on open surfaces versus in bookcases and treatment of samples have been studied. Concentrations of bacteria and endotoxin were significantly higher when occupants were at home than when they were absent. Across homes, higher concentrations of fungi were found in spring than in winter, as was the total inflammatory potential, while higher concentrations of protease were found in winter than in spring. The placement of the EDCs in bookcases versus on an open surface significantly affected the measured concentrations of bacteria and endotoxin. Direct extraction of EDC cloths caused a higher measured concentration of bacteria, fungi and serine protease than if EDC cloths were extracted post-storage at -20 °C. Extraction of EDC cloths caused an average of 51% and 58% extraction of bacteria and fungi respectively. In conclusion, EDCs should be placed on open surfaces during the sampling, how much occupants are present in their home during sampling and sampling season should be considered, EDC cloths should not be stored in a freezer before extraction of microorganisms, but extraction suspensions can be stored at -80 °C without affecting the number of microorganisms significantly.

Effect of endotoxin and allergens on neonatal lung function and infancy respiratory symptoms and eczema

BACKGROUND

Exposure to endotoxin and allergens in house dust has been found to be associated with childhood wheeze and asthma. Neonatal lung function is rarely examined in relation to this exposure.

OBJECTIVES

To assess the association between exposure to endotoxin, house dust mite and cat allergens and neonatal lung function, and respiratory symptoms and eczema in infancy.

METHODS

In the Wheezing Illnesses Study Leidsche Rijn (WHISTLER) birth cohort study, levels of endotoxin, house dust mite allergens, and cat allergen have been measured in dust samples collected in the child's home. Lung function was measured before age 2 months, and respiratory symptoms and eczema were recorded in a daily diary during the first year of life. Associations of lung function (N = 302), respiratory symptoms (N = 361), and eczema (N = 342) with endotoxin and allergen levels have been studied by means of linear and logistic regression, respectively.

RESULTS

Mattress dust endotoxin was associated with a significant increase in neonatal respiratory compliance [adjusted mean difference (95% confidence interval) 2.31 (0.33; 4.29) ml/kPa per interquartile range increase in exposure] and a non-significant decrease in neonatal airway resistance [0.32 (-0.77; 0.14) kPa/l/s]. There were no associations between allergen exposure and neonatal lung function and respiratory symptoms.

CONCLUSIONS

Environmental exposure to endotoxin may have an important role in the development of lung function.

Positive associations between respiratory outcomes and fungal index in rural inhabitants of a representative sample of French dwellings

Our study aims at estimating exposure to molds at home, based on microbial Volatile Organic Compounds (MVOCs) assessment, and evaluating its effect on respiratory diseases in a representative sample of dwellings. In the framework of a national campaign, indoor pollution was monitored in a sample of the 24 million dwellings of metropolitan France (n=567). 727 subjects answered to a standardized questionnaire on respiratory diseases and had MVOCs sampled in their bedrooms and a fungal index (FI) defined. Among the 431 dwellings with complete data, one out of three was contaminated by molds as assessed by a positive FI: 27.0% in urban, 38.2% in periurban and 34.9% in rural dwellings respectively. Positive associations were observed between fungal index and current asthma (8.6%) and chronic bronchitis-like symptoms (8.4%), especially in rural areas (OR=2.95, 95%CI (1.10; 7.95) and 3.35, 95%CI (1.33; 8.48) respectively). Our study, based on objective assessments of fungal contamination, is in agreement with previous results suggesting mold-related respiratory effects. Moreover associations found among rural population could indicate specific pollution and impact in this environment.

Geographical variation and the determinants of domestic endotoxin levels in mattress dust in Europe

Endotoxin exposures have manifold effects on human health. The geographical variation and determinants of domestic endotoxin levels in Europe have not yet been extensively described. To investigate the geographical variation and determinants of domestic endotoxin concentrations in mattress dust in Europe using data collected in the European Community Respiratory Health Survey follow-up (ECRHS II). Endotoxin levels were measured in mattress dust from 974 ECRHS II participants from 22 study centers using an immunoassay. Information on demographic, lifestyle, and housing characteristics of the participants was obtained in face-to-face interviews. The median endotoxin concentration in mattress dust ranged from 772 endotoxin units per gram (EU/g) dust in Reykjavik, Iceland, to 4806 EU/g in Turin, Italy. High average outdoor summer temperature of study center, cat or dog keeping, a high household crowding index, and visible damp patches in the bedroom were significantly associated with a higher endotoxin concentrations in mattress dust. There is a large variability in domestic endotoxin levels across Europe. Average outdoor summer temperature of study center, which explains only 10% of the variation in domestic endotoxin level by center, is the strongest meteorological determinant. The observed variation needs to be taken into account when evaluating the health effects of endotoxin exposures in international contexts.

PRACTICAL IMPLICATIONS

The incoherent observations of the health effects of endotoxin may be partly owing to the geographical heterogeneity of endotoxin exposure. Therefore, the observed variation should be considered in further studies. Measurements of indoor endotoxin are recommended as an indicator for the level of exposures of individual domestic environments.

Airborne fungal volatile organic compounds in rural and urban dwellings: detection of mould contamination in 94 homes determined by visual inspection and airborne fungal volatile organic compounds method

Moulds can both degrade the materials and structures they colonise and contribute to the appearance of symptoms and diseases in the inhabitants of contaminated dwellings. Only few data have compared the levels of contamination in urban and rural environments and the results are not consistent. The aim of this study was to use a fungal contamination index, based on the detection of specific Microbial Volatile Organic Compounds (MVOC), to determine the exposure to moulds of individuals living in urban and rural dwellings. For this purpose, 94 dwellings (47 in an urban setting in Clermont-Ferrand and 47 in rural areas of the Auvergne region, France) were studied. By demonstrating marked disparities between the proportion of visible contamination (19%) and that of active, visible and/or hidden contamination (59%) and the fact that almost all visible contamination was identified by MVOC, we were able to show that use of the index seemed relevant to confirm the actual presence of fungal contamination in a dwelling. Furthermore, it was possible to demonstrate a relationship between moulds and the presence of water on surfaces (condensation, infiltrations, water damage, etc.). A higher proportion of positive fungal contamination index in rural homes was observed compared to the proportion in urban ones (68% versus 49%; p<0.05).

Association between endotoxin and mite allergen exposure with asthma and specific sensitization at age 7 in high-risk children

The role of endotoxin and house dust mite allergen (HDM) in allergen sensitization and asthma is unclear. The timeframe of exposure and asthma assessment appears critical. We aimed to determine, in children at 7 yr of age, the association between current exposure to endotoxin and HDM and risks of recurrent wheeze, paediatric allergist diagnosed asthma and allergen sensitization. Three hundred and eighty children who had an increased risk of asthma because of family background were assessed at age 7 yr by a questionnaire-standardized interview, allergen skin testing and clinical examination by a paediatric allergist. Dust samples were collected from their homes and analysed for levels of endotoxin and HDM (Der p 1 and Der f 1). Levels of endotoxin in dust samples were associated with protection from paediatric allergist diagnosed asthma with inhaled steroid use (OR 0.69, 95% CI 0.53-0.91) and specific sensitization to dog allergen (OR 0.68, 95% CI 0.51-0.90) at the age of 7 yr; both endotoxin and HDM were associated with decreased risk of sensitization to dog allergen. In high-risk children at age 7, endotoxin levels were associated with decreased sensitization to dog, as well as with decreased asthma.

The hygiene hypothesis revisited: role of materno-fetal interactions

For 20 years, the hygiene hypothesis has dominated attempts to explain the increasing prevalence of allergic disease. A causal link between maternal innate immune response during pregnancy and disease protection in the offspring was recently demonstrated. Central to this was a systemically diffused signal that downregulated Toll-like receptor expression in placental tissues. Herein we develop the hypothesis that maternal systemic regulatory mechanisms operational during pregnancy could impact allergic disease risk of the offspring, depending on the type of inflammatory response from which they originate. Classic microbial-derived, mild, subacute inflammation provides a protective signal, whereas allergic inflammation provides a negative one. Mild, subacute inflammation of pregnant women leads to systemically diffused signals manifest in the gestation-associated tissues and by the fetus and newborn as a dampened inflammatory response. The converse is true if the mother has allergic inflammation during pregnancy. In both cases, these impact on development of the airways and of balanced immune function at birth and in early postnatal life. Thus, we seem to be at the dawn of a new incarnation of the hygiene hypothesis in which the pregnant woman's inflammatory response is crucial to determining the child's likelihood of developing allergic disease.