Potential association of vacuum cleaning frequency with an altered gut microbiota in pregnant women and their 2-year-old children

Cleaning

In the IMPACT study, there were 358 mother-child pairs with complete information about
monthly cleaning and vacuum cleaning frequency. The cleaning frequencies were generally
stable throughout the period investigated from late pregnancy until the child was
2 years (Additional file 1: Table S1), with an average frequency of 2.9 washings and 6.6 vacuum cleanings per
month. We found a slight positive correlation between washing and vacuum cleaning
frequencies (R²
?=?0.13, p??0.001, Pearson), while there were very minor or no correlations between cleaning
and introduction of rice, corn, wheat, bread, cooked vegetables, raw vegetables, fruits,
commercial pre-made dinner, homemade dinner, fish, milk, or eggs into infants’ diet
(R²
??0.01, p??0.05, Pearson).

Association between cleaning frequency and the gut microbiota

We found no significant associations for alpha-diversity for any of the age categories,
but for beta-diversity, we found a significant association. Based on the microbiota
composition, the mothers clustered into three distinct clusters (Cluster 1 to 3; Fig. 1), where Cluster 1 showed association with high vacuum cleaning frequency and Cluster
3 with low (p??0.0005, likelihood ratio chi-square test).

Fig. 1. Association between beta-diversity and vacuum cleaning for pregnant mothers. The color code represents the three main clusters detected by Ward’s analyses based on Euclidean
distances for the OTU abundance data

For the compositional association between the microbiota and cleaning frequencies
by ASCA, we found no significant associations for washing, while we detected significant
associations for vacuum cleaning at pregnancy and 2-year children (Figs. 2a and 3a, respectively). However, only a few OTUs were important for these associations (Figs. 2b and 3b, respectively). Random Forest revealed a significant discrimination between high-
and low vacuum cleaning frequency only for mothers (p?=?0.007, Kruskal-Wallis test), while for the 2-year old, this discrimination was
at the border of significance (p?=?0.058; Kruskal-Wallis test). As for the ASCA, only a few OTUs were influential
in the models (Additional file 2: Figure S1).

Fig. 2. Association between the pregnant mother’s microbiota and vacuum cleaning frequency
determined by ASCA analyses. a Overall association of microbiota with vacuum cleaning. b Phylogenetic association of the OTUs contributing to explaining the differences in
the microbiota. The inner circle indicates the importance of the OTUs, where blue indicates positive association and red negative (ASCA loads spanning ±0.6)

Fig. 3. Association between the 2-year microbiota and vacuum cleaning determined by ASCA analyses.
a Overall association of microbiota with vacuum cleaning. b Phylogenetic association of the OTUs contributing to explaining the differences in
the microbiota. The inner circle indicates the importance of the OTUs, where blue indicates positive association and red negative (ASCA loads spanning ±0.6)

At pregnancy, OTU851141 related to Faecalibacterium prausnitzii showed the strongest positive influence on the ASCA model for vacuum cleaning. This
OTU also showed a significant direct association with vacuuming (median 6.3 % (high)
vs 1.8 % (low), p?=?0.006 Kruskal-Wallis test). OTU567381 related to Roseburia faecis was identified as the most influential for Random Forest. This OTU also showed significant
direct association with vacuum cleaning frequency (median 1.2 % (high) vs 0.33 % (low),
p?=?0.003 Kruskal-Wallis test). As for the negative associations during pregnancy,
only OTU584375 related to Bifidobacterium adolescentis was detected as influential by ASCA, with a median of 2.7 % for low vacuum cleaning
and 1.3 % for high vacuum cleaning frequency (p?=?0.034, Kruskal-Wallis test). For the 2-year-olds, OTU1104433 classified as Blautia sp. was the most influential as determined by ASCA (median 4.9 %, vs 2.8 % for high
and low vacuum cleaning frequency, respectively; p?=?0.015 Kruskal-Wallis test), while OTU844941 related to Oscillospira sp. was identified by Random Forest (median 0.23 % vs 0.05 % for high and low vacuum
cleaning frequency, respectively; p?=?0.001, Kruskal-Wallis test).

To determine potential quantitative associations, we investigated the OTUs directly
correlated with vacuum cleaning after FDR correction for mothers and 2-year-old children
using Spearman non-parametric correlation. We identified the same positively associated
OTUs, as identified by ASCA and Random Forest, while the negatively associated OTU
identified by ASCA did not show significance. In addition to the ASCA and Random Forest
identified OTUs, a set of low abundant OTUs were also identified for the Spearman
correlations (Table 1).

Table 1. Direct correlation of OTUs for dust cleaning mother and 2-year children