Environmental and structural factors associated with bacterial diversity in household dust across the Arizona-Sonora border

Abstract

We previously reported that asthma prevalence was higher in the United States (US) compared to Mexico (MX) (25.8% vs. 8.4%). This investigation assessed differences in microbial dust composition in relation to demographic and housing characteristics on both sides of the US-MX Border. Forty homes were recruited in the US and MX. Home visits collected floor dust and documented occupants' demographics, asthma prevalence, housing structure, and use characteristics. US households were more likely to have inhabitants who reported asthma when compared with MX households (30% vs. 5%) and had significantly different flooring types. The percentage of households on paved roads, with flushing toilets, with piped water and with air conditioning was higher in the US, while dust load was higher in MX. Significant differences exist between countries in the microbial composition of the floor dust. Dust from Mexican homes was enriched with Alishewanella, Paracoccus, Rheinheimera genera and Intrasporangiaceae family. A predictive metagenomics analysis identified 68 significantly differentially abundant functional pathways between US and MX. This study documented multiple structural, environmental, and demographic differences between homes in the US and MX that may contribute to significantly different microbial composition of dust observed in these two countries.

Figure 1

(A) Unweighted UniFrac beta diversity plot comparing the United States of America (US) and Mexico (MX) house dust (PERMANOVA pseudo-F = 3.02 p < 0.001, q < 0.0015). (B) Random Forest classifier trained to differentiate the neighborhoods using the dust microbiome compositions. The classifier achieved an overall accuracy of 0.87594. US samples were accurately labeled 87.5100% of the time, and Mexican samples were accurately labeled 89% of the time. (C) Unweighted UniFrac beta diversity plot comparing high SES NMX neighborhood vs low SES NMX, vs NUS vs TUS. (D) Random Forest classifier trained to differentiate the neighborhoods using the dust microbiome compositions the model predicted NUS accurately 10,075% of the time; TUS 560% of the time: high SES NMX 75% of the time; and low SES NMX 100% of the time. LSES = low socioeconomic status Nogales, Sanora, Mexico; HSES = high socioeconomic status Nogales, Sanora, Mexico; MX = Mexico; USA = United States of America.

Figure 2

ANCOM and Sample Classifier comparing the house dust from homes in the United States versus Mexico. Top is Mexico and bottom is United States of America. The x-axes in these figures represent the relative abundance of the taxon that is highlighted in the panel, while the y-axes represent the categorizations of the samples. Each point therefore represents the relative abundance of a taxon in a single sample, and the box plots and the histograms show the distribution of the relative abundances in each sample group.