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. 2021 Jun 24;16(6):e0244341.
doi: 10.1371/journal.pone.0244341. eCollection 2021.

Exposure to traffic-related air pollution and bacterial diversity in the lower respiratory tract of children

Christine Niemeier-Walsh  1 , Patrick H Ryan  1   2   3 , Jaroslaw Meller  1   2 , Nicholas J Ollberding  2   3 , Atin Adhikari  4 , Tiina Reponen  1
Affiliations

Exposure to traffic-related air pollution and bacterial diversity in the lower respiratory tract of children

Christine Niemeier-Walsh et al. PLoS One. .

Abstract

Background: Exposure to particulate matter has been shown to increase the adhesion of bacteria to human airway epithelial cells. However, the impact of traffic-related air pollution (TRAP) on the respiratory microbiome is unknown.

Methods: Forty children were recruited through the Cincinnati Childhood Allergy and Air Pollution Study, a longitudinal cohort followed from birth through early adolescence. Saliva and induced sputum were collected at age 14 years. Exposure to TRAP was characterized from birth through the time of sample collection using a previously validated land-use regression model. Sequencing of the bacterial 16S and ITS fungal rRNA genes was performed on sputum and saliva samples. The relative abundance of bacterial taxa and diversity indices were compared in children with exposure to high and low TRAP. We also used multiple linear regression to assess the effect of TRAP exposure, gender, asthma status, and socioeconomic status on the alpha diversity of bacteria in sputum.

Results: We observed higher bacterial alpha diversity indices in sputum than in saliva. The diversity indices for bacteria were greater in the high TRAP exposure group than the low exposure group. These differences remained after adjusting for asthma status, gender, and mother's education. No differences were observed in the fungal microbiome between TRAP exposure groups.

Conclusion: Our findings indicate that exposure to TRAP in early childhood and adolescence may be associated with greater bacterial diversity in the lower respiratory tract. Asthma status does not appear to confound the observed differences in diversity. These results demonstrate that there may be a TRAP-exposure related change in the lower respiratory microbiota that is independent of asthma status.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Box plots comparing bacterial alpha diversity indices between sputum and saliva, including Shannon diversity, number of observed amplicon sequence variants (ASVs), and Faith’s phylogenetic diversity.
Fig 2
Fig 2. Non-metric multidimensional scaling (NMDS) of Bray-Curtis distances of bacteria in saliva and sputum samples.
Fig 3
Fig 3. Box plots comparing bacterial diversity indices in sputum between high and low traffic-related air pollution (TRAP) exposure groups; Shannon diversity, number of observed amplicon sequence variants (ASVs), and Faith’s phylogenetic diversity.
Fig 4
Fig 4. Non-metric multidimensional scaling (NMDS) of Bray-Curtis distances of bacteria in sputum microbiota from each TRAP exposure group, asthma status group, and gender.
Fig 5
Fig 5
Bar plots showing the relative abundance of bacterial phyla in sputum across (A) TRAP exposure groups, (B) asthma status groups, and (C) genders.
Fig 6
Fig 6. DESeq2 results showing the log2 fold-change values (x-axis) of bacteria in sputum between TRAP exposure groups.
Each line on the y-axis indicates the family, each point represents an individual ASV within that family, and the color of the point indicates the phylum.
Fig 7
Fig 7. Violin plot comparing the total bacterial load, as measured by qPCR, in the sputum of each TRAP exposure group, each asthma status group, and each gender.
See this image and copyright information in PMC

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