Daycare environment, nasal microbiota, and respiratory health in young children – CRESMINA

Dust microbiota: Dust samples were collected in 103 of the 108 daycare centers included in the study using a vacuum-based sampling system. The composition of the bacterial microbiota in dust was assessed by 16S rRNA sequencing (a “marker gene” approach allowing identification of the bacteria present in a sample).

Nasal microbiota: Nasal samples (swabs) were collected for children under 1 year of age at inclusion. Sampling was performed at home by one of the parents using a dedicated kit. The first sample was collected a few months after the visit to the child’s daycare center. A second sample was collected at the age of 2 years. Detailed illustrated instructions and a video were provided to parents. In total, 205 samples were collected (first sampling for 126 children, second sampling for 79 children) up to summer 2023. Two sequencing methods were applied to characterize the nasal microbiota: 16S rRNA sequencing and whole-genome sequencing (a more precise method).

Respiratory health follow-up: Follow-up questionnaires focusing on children’s respiratory health were sent in summer 2022, winter 2022, and summer 2023 (web-based questionnaires). Telephone follow-up will also be conducted.

Analyses: The first analyses aimed to identify daycare exposures that are detrimental to children’s respiratory health, in particular the role of dust microbiota, exposure to cleaning products, and exposure to indoor air pollutants. Associations between the nasal microbiota and children’s respiratory health were also examined in the subpopulation of children under 1 year of age at inclusion. Across all analyses, wheezing symptoms at inclusion (which may be suggestive of asthma) were characterized in three ways: ever wheezing (32%), recurrent wheezing (≥3 episodes since birth, 13%), and wheezing with the use of inhaled corticosteroids (ICS, 15%).

Daycare dust microbiota and children’s respiratory health: Four microbiota profiles were identified using a classification approach. After accounting for age, the number of children per daycare center, and season, one microbiota profile was associated with a higher risk of recurrent wheezing.

Exposure to cleaning and disinfection products and children’s respiratory health: High use (in terms of frequency and number) of cleaning products in daycare centers was associated with an increased risk of ever wheezing and wheezing with inhaled corticosteroids (ICS). These results accounted for the child’s age, parental smoking status, and parental educational level.

Exposure to indoor air pollutants and children’s respiratory health: Concentrations of 54 indoor air pollutants measured in daycare centers were analyzed. Higher concentrations of four of these pollutants were associated with ever wheezing, with similar results observed for other wheezing symptoms. The analyses accounted for the child’s age, parental smoking status, and educational level.

Nasal microbiota: First analyses focused on the composition of the nasal microbiota characterized by 16S rRNA sequencing. No significant associations were observed between nasal microbiota composition and daycare exposures such as exposure to cleaning and disinfection products or environmental microbiota profiles, nor between nasal microbiota composition and wheezing in children. In future analyses, whole-genome sequencing (WGS) data (providing a more detailed characterization of the nasal microbiota) will be used.

Our results identified several early determinants of children’s respiratory health in the daycare environment. They show, for the first time in the literature, that (1) certain dust microbiota profiles, (2) high use of cleaning and disinfection products, and (3) exposure to certain indoor air pollutants in daycare centers are associated with the risk of wheezing in young children. Accordingly, measures aimed at limiting children’s exposure to cleaning and disinfection products in daycare centers are recommended. Future studies seeking to identify the determinants of dust microbiota and the sources of harmful indoor air pollutants could help to develop preventive strategies.

No scientific article related to this project has been published yet

Asthma is a common chronic respiratory disease, which can cause lifelong respiratory morbidity. It is widely accepted that asthma has origins early in life. Microbial and chemical exposures are two important risk factors for asthma in young children, but current knowledge remains insufficient to develop efficient prevention strategies. The recent development of high-throughput sequencing approaches to characterize both the environmental and the human microbiome has strengthened evidence for the role of microbial communities in asthma pathogenesis. This emerging field is seen as a major opportunity to provide new insight into the pathways linking early-life environment to disease development. However, major questions remain regarding (1) the exact role of specific airway microbiota profiles, and their evolution, in asthma development; (2) the impact of modifiable risk factors in the early-life environment on airway microbiota; and (3) whether airway microbiota mediates and/or modulates the environment-asthma association. The need for large, prospective studies with repeated assessment of airway microbiota in early life has been emphasized.
Our proposal is centered on young children attending daycares, an environment where many of them spend a high amount of time, and which is thought to impact asthma risk. The central goal of the CRESMINA project is to study the relationships between daycare environment, nasal microbiota, and respiratory health in young children attending daycare centers, with 3 specific aims: (1) to determine the association of environmental exposures in daycare with baseline and longitudinal nasal microbiota profiles, for the following daycare-related exposures: number and characteristics of occupants, environmental microbiota (settled dust), indoor air chemical exposures and cleaning/disinfection practices; (2) to determine the association of baseline and longitudinal nasal microbiota profiles with respiratory health (primary outcome: longitudinal wheezing phenotypes from infancy to age 4 years); (3) to examine the mediating and/or modulating role of nasal microbiota in the association between environmental exposures in daycare and respiratory health.
These questions will be examined in the CRESPI study (Respiratory health of Children in daycare), a cohort of 2000 children attending daycare in Paris region, which will be initiated in January 2019 in the context of an ANSES-funded project (CRESPINET), and will include detailed characterization of chemical exposures in daycare centers. The CRESMINA proposal builds on the subset of infants (age <1 year at baseline, n~800) enrolled in the CRESPI cohort. We plan to: characterize the children’s nasal microbiota based on two nasal swab collections, in infancy and at age 24 months; improve characterization of daycare environment by measuring environmental microbiota in settled dust; and improve characterization of respiratory health outcomes by extending follow-up until age 4 years. Composition of both nasal and environment microbiota will be characterized by 16S rRNA gene sequencing, using methods recommended by the NIH Human Microbiome Projects. Statistical analyses of Aims 1 to 3 will include characterization of baseline/longitudinal microbiota profiles and longitudinal wheezing profiles through clustering approaches, multinomial logistic regression models with adjustment for a large set of potential confounders, and use of recent methods (marginal structural models) for mediation analysis based on causal inference approaches.
In summary, the CRESMINA project will identify specific nasal microbiota profiles differentially associated with early-life determinants of asthma and with poor respiratory outcomes; and disentangle their potential mediating / modulating roles. This knowledge could be key to the development of targeted strategies to modulate risk of developing asthma in children.