Exposure to Antibacterial Chemicals Is Associated With Altered Composition of Oral Microbiome

Abstract

Antimicrobial chemicals are used as preservatives in cosmetics, pharmaceuticals, and food to prevent the growth of bacteria and fungi in the products. Unintentional exposure in humans to such chemicals is well documented, but whether they also interfere with human oral microbiome composition is largely unexplored. In this study, we explored whether the oral bacterial composition is affected by exposure to antibacterial and environmental chemicals. Gingival fluid, urine, and interview data were collected from 477 adults (18-47 years) from the RHINESSA study in Bergen, Norway. Urine biomarkers of triclosan, triclocarban, parabens, benzophenone-3, bisphenols, and 2,4- and 2,5-dichlorophenols (DCPs) were quantified (by mass spectrometry). Microbiome analysis was based on 16S amplicon sequencing. Diversity and differential abundance analyses were performed to identify how microbial communities may change when comparing groups of different chemical exposure. We identified that high urine levels (>75th percentile) of propyl parabens were associated with a lower abundance of bacteria genera TM7 [G-3], Helicobacter, Megasphaera, Mitsuokella, Tannerella, Propionibacteriaceae [G-2], and Dermabacter, as compared with low propylparaben levels (<25^th percentile). High exposure to ethylparaben was associated with a higher abundance of Paracoccus. High urine levels of bisphenol A were associated with a lower abundance of Streptococcus and exposure to another environmental chemical, 2,4-DCP, was associated with a lower abundance of Treponema, Fretibacterium, and Bacteroidales [G-2]. High exposure to antibacterial and environmental chemicals was associated with an altered composition of gingiva bacteria; mostly commensal bacteria in the oral cavity. Our results highlight a need for a better understanding of how antimicrobial chemical exposure influences the human microbiome.

Keywords: ANCOM-BC; RHINESSA; chemicals; differential abundance; oral microbiome.

Figure 1

Percent of urine samples with urine biomarker above the limit of detection (LOD).

Figure 2

Box plot of Shannon diversity index at the genus level. In the box plot, the lower and upper hinges correspond to the first and third quartiles (the 25th and 75th percentiles). The median is represented by a solid line within the box. The upper whisker extends from the hinge to the largest value (maxima) no further than 1.5 times interquartile range (IQR, distance between the first and third quartiles) from the hinge, the lower whisker extends from the hinge to the smallest value (minima) at most 1.5 times IQR of the hinge. Data beyond the end of the whiskers are called “outlying” points. N = 477 samples examined over study groups (denoted by different colors) and the data points are overlaid in each box. p values were given by Wilcoxon rank-sum test. (A) Methylparaben; (B) propylparaben; and (C) benzophenone-3.

Figure 3

Principal coordinates analysis (PCoA) plot of the oral microbiome beta diversity (Bray–Curtis dissimilarity) at the genus level. Ellipses stand for 68% of data coverage. Lines are connected between samples and the corresponding group spatial median. p values from both PERMANOVA and PERMDISP tests are given in the plot. (A) Methylparaben; (B) propylparaben; (C) molar sum of parabens; and (D) 2,4-dichlorophenol.

Figure 4

Pie charts representing the main phyla that constitute the oral microbiome in the study population.

Figure 5

Bar plot of differentially abundant genera obtained from ANCOM-BC pairwise analysis. Data are represented by log-fold change (shown as a column) ± SE (shown as error bars). All log fold changes with p < 0.05 are indicated, *significant at 5% level of significance; **significant at 1% level of significance; and ***significant at 0.1% level of significance. (A) Ethylparaben; (B) propylparaben; (C) bisphenol A; (D) 2,4-DCP; (E) butylparaben; and (F) triclocarban.

Figure 6

Overview of the ANCOM-BC results. Only taxa with a p < 0.01 were presented. Chemicals with sidebar color in orange were categorized into quartiles and chemicals with sidebar color in purple were categorized into below and above the limit of detection. Check mark “✓”: taxon was identified to be differentially abundant in at least one quartile of the chemical; downward arrow “”: taxon was identified to be monotonically decreasing as the increase of the chemical concentration; upward arrow “”: taxon was identified to be monotonically increasing as the chemical concentration increased.